WorldWideScience

Sample records for wave gas sensors

  1. Vehicle exhaust gas chemical sensors using acoustic wave resonators

    Energy Technology Data Exchange (ETDEWEB)

    Cernosek, R.W.; Small, J.H.; Sawyer, P.S.; Bigbie, J.R. [Sandia National Labs., Albuquerque, NM (United States); Anderson, M.T. [3M Industrial and Consumer Sector Research Lab., St. Paul, MN (United States)

    1998-03-01

    Under Sandia`s Laboratory Directed Research and Development (LDRD) program, novel acoustic wave-based sensors were explored for detecting gaseous chemical species in vehicle exhaust streams. The need exists for on-line, real-time monitors to continuously analyze the toxic exhaust gases -- nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC) -- for determining catalytic converter efficiency, documenting compliance to emission regulations, and optimizing engine performance through feedback control. In this project, the authors adapted existing acoustic wave chemical sensor technology to the high temperature environment and investigated new robust sensor materials for improving gas detection sensitivity and selectivity. This report describes one new sensor that has potential use as an exhaust stream residual hydrocarbon monitor. The sensor consists of a thickness shear mode (TSM) quartz resonator coated with a thin mesoporous silica layer ion-exchanged with palladium ions. When operated at temperatures above 300 C, the high surface area film catalyzes the combustion of the hydrocarbon vapors in the presence of oxygen. The sensor acts as a calorimeter as the exothermic reaction slightly increases the temperature, stressing the sensor surface, and producing a measurable deviation in the resonator frequency. Sensitivities as high as 0.44 (ppm-{Delta}f) and (ppm-gas) have been measured for propylene gas, with minimum detectable signals of < 50 ppm of propylene at 500 C.

  2. Langasite surface acoustic wave gas sensors: modeling and verification

    Energy Technology Data Exchange (ETDEWEB)

    Peng Zheng,; Greve, D. W.; Oppenheim, I. J.

    2013-03-01

    We report finite element simulations of the effect of conductive sensing layers on the surface wave velocity of langasite substrates. The simulations include both the mechanical and electrical influences of the conducting sensing layer. We show that three-dimensional simulations are necessary because of the out-of-plane displacements of the commonly used (0, 138.5, 26.7) Euler angle. Measurements of the transducer input admittance in reflective delay-line devices yield a value for the electromechanical coupling coefficient that is in good agreement with the three-dimensional simulations on bare langasite substrate. The input admittance measurements also show evidence of excitation of an additional wave mode and excess loss due to the finger resistance. The results of these simulations and measurements will be useful in the design of surface acoustic wave gas sensors.

  3. Gas Sensors: A Review

    Directory of Open Access Journals (Sweden)

    Zainab Yunusa

    2014-04-01

    Full Text Available In this paper a review of different technologies for gas sensors is presented. The different types of gas sensors technologies including catalytic gas sensor, electrochemical gas sensors, thermal conductivity gas sensor, optical gas sensor and acoustic gas sensor are discussed together with their principle of operation. The Surface Acoustic Wave Gas Sensor technology is discussed in greater detail. The advantages and disadvantages of each sensor technology are also highlighted. All these technologies have been used for several decades for the development of highly sensitive and responsive gas sensors for the detection of flammable and hazardous gases. However, for improved sensitivity and selectivity for these sensors, future trends and outlook for researchers are suggested in the conclusion of this article.

  4. Gas Sensor

    KAUST Repository

    Luebke, Ryan

    2015-01-22

    A gas sensor using a metal organic framework material can be fully integrated with related circuitry on a single substrate. In an on-chip application, the gas sensor can result in an area-efficient fully integrated gas sensor solution. In one aspect, a gas sensor can include a first gas sensing region including a first pair of electrodes, and a first gas sensitive material proximate to the first pair of electrodes, wherein the first gas sensitive material includes a first metal organic framework material.

  5. Design of a Low Voltage 0.18 mm CMOS Surface Acoustic Wave Gas Sensor

    Directory of Open Access Journals (Sweden)

    M. MOGHAVVEMI

    2011-02-01

    Full Text Available a Surface Acoustic Wave (SAW gas sensor is designed and tested in this paper. The objective of the designed SAW Gas sensor is to detect H2S and NOX gases. The inter-digital transducers (IDT antennas in the proposed sensor are coated with thin film WO3, which mass is sensitive to mentioned gas concentrations upon close contact. The changes in WO3 mass are registered as frequency shift from 300 to 500 MHz. The sensor blocks are simulated, fabricated and tested for an operating frequency of 300 MHz to 350 MHz. A relatively linear response is achieved with a step of 0.1 V for 10 MHz step frequency shift emitted from WO3 coated IDTs. This fully integrated signal processing circuitry designed by 0.18 mm CMOS process is simple, cost effective, small in size, has low power consumption, and fast real-time operation response as well.

  6. Temporal window system: A new approach for dynamic detection application to surface acoustic wave gas sensors

    Energy Technology Data Exchange (ETDEWEB)

    Bordieu, C.; Rebiere, D.; Pistre, J. [and others

    1996-12-31

    Pattern recognition techniques based on artificial neural networks are now frequently used with good results for gas sensor signal processing (this includes the detection, the identification and the quantification of gases). In the literature, data sets needed for neural networks are practically always built with steady state sensor responses. This situation prevents these techniques from being used in real time applications. Nevertheless, for example in the case of surface acoustic wave (SAW) gas sensors, because of quite long response times due to kinetic factors concerning the gas adsorption and because gases are sometimes extremely dangerous and/or toxic (NO{sub x}, SO{sub 2}, organophosphorus compounds,...), the detection speed is an essential parameter and hence must be monitored in a real time mode. The purpose of this paper is to propose a new dynamic approach and to illustrate it with SAW sensor responses.

  7. An Improved Negative Pressure Wave Method for Natural Gas Pipeline Leak Location Using FBG Based Strain Sensor and Wavelet Transform

    Directory of Open Access Journals (Sweden)

    Qingmin Hou

    2013-01-01

    Full Text Available Methods that more quickly locate leakages in natural gas pipelines are urgently required. In this paper, an improved negative pressure wave method based on FBG based strain sensors and wavelet analysis is proposed. This method takes into account the variation in the negative pressure wave propagation velocity and the gas velocity variation, uses the traditional leak location formula, and employs Compound Simpson and Dichotomy Searching for solving this formula. In addition, a FBG based strain sensor instead of a traditional pressure sensor was developed for detecting the negative pressure wave signal produced by leakage. Unlike traditional sensors, FBG sensors can be installed anywhere along the pipeline, thus leading to high positioning accuracy through more frequent installment of the sensors. Finally, a wavelet transform method was employed to locate the pressure drop points within the FBG signals. Experiment results show good positioning accuracy for natural gas pipeline leakage, using this new method.

  8. Simultaneous measurement of gas concentration and temperature by the ball surface acoustic wave sensor

    Science.gov (United States)

    Yamanaka, Kazushi; Akao, Shingo; Takeda, Nobuo; Tsuji, Toshihiro; Oizumi, Toru; Tsukahara, Yusuke

    2017-07-01

    We have developed a ball surface acoustic wave (SAW) trace moisture sensor with an amorphous silica sensitive film and realized wide-range measurement from 0.017 ppmv [a frost point (FP) of -99 °C] to 6.0 × 103 ppmv (0 °C FP). However, since the sensitivity of the sensor depends on the temperature, measurement results are disturbed when the temperature largely changes. To overcome this problem, we developed a method to simultaneously measure temperature and gas concentration using a ball SAW sensor. Temperature and concentration is derived by solving equations for the delay time change at two frequencies. When the temperature had a large jump, the delay time change was significantly disturbed, but the water concentration was almost correctly measured, by compensating the sensitivity change using measured temperature. The temperature measured by a ball SAW sensor will also be used to control the ball temperature. This method will make a ball SAW sensor reliable in environments of varying temperatures.

  9. Fast Surface Acoustic Wave-Based Sensors to Investigate the Kinetics of Gas Uptake in Ultra-Microporous Frameworks.

    Science.gov (United States)

    Paschke, Benjamin; Wixforth, Achim; Denysenko, Dmytro; Volkmer, Dirk

    2017-06-23

    Observation of the kinetics and measurement of the activation energies for gas diffusion in porous materials requires very fast and sensitive sensors. In this work, thin films of metal-organic frameworks (MOFs) with different pore sizes are grown on a surface acoustic wave (SAW) substrate, resulting in very sensitive and specific sensor systems for the detection of various gases at very short time scales. Using specially designed SAW delay lines for the detection, up to 200-nm-wide cubic MOF crystals were grown directly from a solution on the sensitive sensor chip area. One example, MFU-4, exhibits a smallest pore aperture of 2.5 Å and shows a highly sensitive and specific response to CO2, H2, He, NH3, and H2O. It is shown that such a MOF@SAW sensor responds within milliseconds to gas loading and its sensitivity reaches levels as low as 1 ppmv, currently only limited by the gas mixing system. This unique combination of sensitivity and fast response characteristics allows even for real-time investigations of the sorption kinetics during gas uptake and release. As is typical for SAW sensors, the production of the chips is very straightforward and inexpensive and-combined with the unique properties of the MOFs with their tunable pore sizes and adjustable internal surface properties-holds promise for different sensor applications.

  10. An Effective Quality Control of Pharmacologically Active Volatiles of Houttuynia cordata Thunb by Fast Gas Chromatography-Surface Acoustic Wave Sensor

    National Research Council Canada - National Science Library

    Oh, Se Yeon

    2015-01-01

    Fast gas chromatography-surface acoustic wave sensor (GC/SAW) has been applied for the detection of the pharmacological volatiles emanated from Houttuynia cordata Thunb which is from South Korea. H...

  11. Titanium Dioxide-Based 64∘ YX LiNbO3 Surface Acoustic Wave Hydrogen Gas Sensors

    Directory of Open Access Journals (Sweden)

    A. Z. Sadek

    2008-01-01

    Full Text Available Amorphous titanium dioxide (TiO2 and gold (Au doped TiO2-based surface acoustic wave (SAW sensors have been investigated as hydrogen gas detectors. The nanocrystal-doped TiO2 films were synthesized through a sol-gel route, mixing a Ti-butoxide-based solution with diluted colloidal gold nanoparticles. The films were deposited via spin coating onto 64∘ YX LiNbO3 SAW transducers in a helium atmosphere. The SAW gas sensors were operated at various temperatures between 150 and 310∘C. It was found that gold doping on TiO2 increased the device sensitivity and reduced the optimum operating temperature.

  12. Fiber optic gas sensor

    Science.gov (United States)

    Chen, Peng (Inventor); Buric, Michael P. (Inventor); Swinehart, Philip R. (Inventor); Maklad, Mokhtar S. (Inventor)

    2010-01-01

    A gas sensor includes an in-fiber resonant wavelength device provided in a fiber core at a first location. The fiber propagates a sensing light and a power light. A layer of a material is attached to the fiber at the first location. The material is able to absorb the gas at a temperature dependent gas absorption rate. The power light is used to heat the material and increases the gas absorption rate, thereby increasing sensor performance, especially at low temperatures. Further, a method is described of flash heating the gas sensor to absorb more of the gas, allowing the sensor to cool, thereby locking in the gas content of the sensor material, and taking the difference between the starting and ending resonant wavelengths as an indication of the concentration of the gas in the ambient atmosphere.

  13. Characterization of an array of Love-wave gas sensors developed using electrospinning technique to deposit nanofibers as sensitive layers.

    Science.gov (United States)

    Matatagui, D; Fernández, M J; Fontecha, J; Sayago, I; Gràcia, I; Cané, C; Horrillo, M C; Santos, J P

    2014-03-01

    The electrospinning technique has allowed that very different materials are deposited as sensitive layers on Love-wave devices forming a low cost and successful sensor array. Their excellent sensitivity, good linearity and short response time are reported in this paper. Several materials have been used to produce the nanofibers: polymers as Polyvinyl alcohol (PVA), Polyvinylpyrrolidone (PVP) and Polystirene (PS); composites with polymers as PVA+SnCl4; combined polymers as PS+Poly(styrene-alt-maleic anhydride) (PS+PSMA) and metal oxides (SnO2). In order to test the array, well-known chemical warfare agent simulants (CWAs) have been chosen among the volatile organic compounds due to their importance in the security field. Very low concentrations of these compounds have been detected by the array, such as 0.2 ppm of DMMP, a simulant of sarin nerve gas, and 1 ppm of DPGME, a simulant of nitrogen mustard. Additionally, the CWA simulants used in the experiment have been discriminated and classified using pattern recognition techniques, such as principal component analysis and artificial neural networks. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Microfabricated Formaldehyde Gas Sensors

    OpenAIRE

    Cheung, Karen C.; Ko, Frank K.; Jonas Flueckiger

    2009-01-01

    Formaldehyde is a volatile organic compound that is widely used in textiles, paper, wood composites, and household materials. Formaldehyde will continuously outgas from manufactured wood products such as furniture, with adverse health effects resulting from prolonged low-level exposure. New, microfabricated sensors for formaldehyde have been developed to meet the need for portable, low-power gas detection. This paper reviews recent work including silicon microhotplates for metal oxide-based d...

  15. Shock Waves in Gas Dynamics

    Directory of Open Access Journals (Sweden)

    Abdolrahman Razani

    2007-11-01

    Full Text Available Shock wave theory was studied in literature by many authors. This article presents a survey with references about various topics related to shock waves: Hyperbolic conservation laws, Well-posedness theory, Compactness theory, Shock and reaction-diffusion wave, The CJ and ZND theory, Existence of detonation in Majda's model, Premixed laminar flame, Multidimensional gas flows, Multidimensional Riemann problem.

  16. Electrodes for Semiconductor Gas Sensors

    Science.gov (United States)

    Lee, Sung Pil

    2017-01-01

    The electrodes of semiconductor gas sensors are important in characterizing sensors based on their sensitivity, selectivity, reversibility, response time, and long-term stability. The types and materials of electrodes used for semiconductor gas sensors are analyzed. In addition, the effect of interfacial zones and surface states of electrode–semiconductor interfaces on their characteristics is studied. This study describes that the gas interaction mechanism of the electrode–semiconductor interfaces should take into account the interfacial zone, surface states, image force, and tunneling effect. PMID:28346349

  17. Liquid level sensor using ultrasonic Lamb waves.

    Science.gov (United States)

    Sakharov, V E; Kuznetsov, S A; Zaitsev, B D; Kuznetsova, I E; Joshi, S G

    2003-06-01

    This paper describes a novel, noninvasive method for measurement of liquid level in closed metal tanks that are under high pressure. It is based on the use of ultrasonic Lamb waves propagating along the tank wall. Contact with liquid substantially changes the characteristics of these waves and this can be used as an indicator of liquid presence. Theoretical analysis shows that the symmetric and antisymmetric Lamb wave modes, both fundamental and higher order, are sensitive to presence of the liquid. The optimal wave frequency depends on the thickness of the tank wall and wall material. A prototype level sensor based on this principle has been developed. It uses two pairs of wedge transducers to generate and detect Lamb waves propagating along the circumference of the gas tank. An operating frequency of 100 kHz is found to be optimal for use with tanks having a wall thickness of 30-50 mm. Prototype sensors developed under this program have been used successfully in oil fields in the far northern region of Russia.

  18. Surface acoustic wave sensors/gas chromatography; and Low quality natural gas sulfur removal and recovery CNG Claus sulfur recovery process

    Energy Technology Data Exchange (ETDEWEB)

    Klint, B.W.; Dale, P.R.; Stephenson, C.

    1997-12-01

    This topical report consists of the two titled projects. Surface Acoustic Wave/Gas Chromatography (SAW/GC) provides a cost-effective system for collecting real-time field screening data for characterization of vapor streams contaminated with volatile organic compounds (VOCs). The Model 4100 can be used in a field screening mode to produce chromatograms in 10 seconds. This capability will allow a project manager to make immediate decisions and to avoid the long delays and high costs associated with analysis by off-site analytical laboratories. The Model 4100 is currently under evaluation by the California Environmental Protection Agency Technology Certification Program. Initial certification focuses upon the following organics: cis-dichloroethylene, chloroform, carbon tetrachloride, trichlorethylene, tetrachloroethylene, tetrachloroethane, benzene, ethylbenzene, toluene, and o-xylene. In the second study the CNG Claus process is being evaluated for conversion and recovery of elemental sulfur from hydrogen sulfide, especially found in low quality natural gas. This report describes the design, construction and operation of a pilot scale plant built to demonstrate the technical feasibility of the integrated CNG Claus process.

  19. An Effective Quality Control of Pharmacologically Active Volatiles of Houttuynia cordata Thunb by Fast Gas Chromatography-Surface Acoustic Wave Sensor

    Directory of Open Access Journals (Sweden)

    Se Yeon Oh

    2015-06-01

    Full Text Available Fast gas chromatography-surface acoustic wave sensor (GC/SAW has been applied for the detection of the pharmacological volatiles emanated from Houttuynia cordata Thunb which is from South Korea. H. cordata Thunb with unpleasant and fishy odors shows a variety of pharmacological activities such as anti-microbial, anti-inflammatory, anti-cancer, and insect repellent. The aim of this study is to show a novel quality control by GC/SAW methodology for the discrimination of the three different parts of the plant such as leaves, aerial stems, and underground stems for H. cordata Thunb. Sixteen compounds were identified. β-Myrcene, cis-ocimene and decanal are the dominant volatiles for leaves (71.0% and aerial stems (50.1%. While, monoterpenes (74.6% are the dominant volatiles for underground stems. 2-Undecanone (1.3% and lauraldehyde (3.5% were found to be the characteristic components for leaves. Each part of the plant has its own characteristic fragrance pattern owing to its individual chemical compositions. Moreover, its individual characteristic fragrance patterns are conducive to discrimination of the three different parts of the plant. Consequently, fast GC/SAW can be a useful analytical method for quality control of the different parts of the plant with pharmacological volatiles as it provides second unit analysis, a simple and fragrant pattern recognition.

  20. Nanowire-based gas sensors

    NARCIS (Netherlands)

    Chen, X.; Wong, C.K.Y.; Yuan, C.A.; Zhang, G.

    2013-01-01

    Gas sensors fabricated with nanowires as the detecting elements are powerful due to their many improved characteristics such as high surface-to-volume ratios, ultrasensitivity, higher selectivity, low power consumption, and fast response. This paper gives an overview on the recent process of the

  1. Dual-Mode Gas Sensor Composed of a Silicon Nanoribbon Field Effect Transistor and a Bulk Acoustic Wave Resonator: A Case Study in Freons.

    Science.gov (United States)

    Chang, Ye; Hui, Zhipeng; Wang, Xiayu; Qu, Hemi; Pang, Wei; Duan, Xuexin

    2018-01-25

    In this paper, we develop a novel dual-mode gas sensor system which comprises a silicon nanoribbon field effect transistor (Si-NR FET) and a film bulk acoustic resonator (FBAR). We investigate their sensing characteristics using polar and nonpolar organic compounds, and demonstrate that polarity has a significant effect on the response of the Si-NR FET sensor, and only a minor effect on the FBAR sensor. In this dual-mode system, qualitative discrimination can be achieved by analyzing polarity with the Si-NR FET and quantitative concentration information can be obtained using a polymer-coated FBAR with a detection limit at the ppm level. The complementary performance of the sensing elements provides higher analytical efficiency. Additionally, a dual mixture of two types of freons (CFC-113 and HCFC-141b) is further analyzed with the dual-mode gas sensor. Owing to the small size and complementary metal-oxide semiconductor (CMOS)-compatibility of the system, the dual-mode gas sensor shows potential as a portable integrated sensing system for the analysis of gas mixtures in the future.

  2. Sensitivity analysis of steering-wheel gas sensor against diverse core air hole sizes and core materials in terahertz wave band

    Science.gov (United States)

    Ramachandran, A.; Babu, P. Ramesh; Senthilnathan, K.

    2017-11-01

    We design a photonic crystal fiber (PCF) based gas sensor, which works based on evanescent field, by introducing a steering-wheel shape of large noncircular air-hole structure in the cladding region. Further, using the full-vectorial finite element method (FEM), we compute the relative sensitivities of the proposed sensor as 83% and 91% when the operating frequencies are 1THz and 0.5THz, respectively. The proposed sensor is suitable for detecting any kind of chemical and biological gases.

  3. Surface Acoustic Wave Strain Sensor Model

    OpenAIRE

    Wilson, William; Gary ATKINSON

    2011-01-01

    NASA Langley Research Center is investigating Surface Acoustic Wave (SAW) sensor technology for harsh environments aimed at aerospace applications. To aid in development of sensors a model of a SAW strain sensor has been developed. The new model extends the modified matrix method to include the response of Orthogonal Frequency Coded (OFC) reflectors and the response of SAW devices to strain. These results show that the model accurately captures the strain response of a SAW sensor on a Langasi...

  4. Gas sensor with attenuated drift characteristic

    Science.gov (United States)

    Chen, Ing-Shin [Danbury, CT; Chen, Philip S. H. [Bethel, CT; Neuner, Jeffrey W [Bethel, CT; Welch, James [Fairfield, CT; Hendrix, Bryan [Danbury, CT; Dimeo, Jr., Frank [Danbury, CT

    2008-05-13

    A sensor with an attenuated drift characteristic, including a layer structure in which a sensing layer has a layer of diffusional barrier material on at least one of its faces. The sensor may for example be constituted as a hydrogen gas sensor including a palladium/yttrium layer structure formed on a micro-hotplate base, with a chromium barrier layer between the yttrium layer and the micro-hotplate, and with a tantalum barrier layer between the yttrium layer and an overlying palladium protective layer. The gas sensor is useful for detection of a target gas in environments susceptible to generation or incursion of such gas, and achieves substantial (e.g., >90%) reduction of signal drift from the gas sensor in extended operation, relative to a corresponding gas sensor lacking the diffusional barrier structure of the invention

  5. Gas Sensors Based on Conducting Polymers

    Directory of Open Access Journals (Sweden)

    Gaoquan Shi

    2007-03-01

    Full Text Available The gas sensors fabricated by using conducting polymers such as polyaniline (PAni, polypyrrole (PPy and poly (3,4-ethylenedioxythiophene (PEDOT as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review.

  6. Surface Acoustic Wave Strain Sensor Model

    Directory of Open Access Journals (Sweden)

    William WILSON

    2011-04-01

    Full Text Available NASA Langley Research Center is investigating Surface Acoustic Wave (SAW sensor technology for harsh environments aimed at aerospace applications. To aid in development of sensors a model of a SAW strain sensor has been developed. The new model extends the modified matrix method to include the response of Orthogonal Frequency Coded (OFC reflectors and the response of SAW devices to strain. These results show that the model accurately captures the strain response of a SAW sensor on a Langasite substrate. The results of the model of a SAW Strain Sensor on Langasite are presented.

  7. Wave effects on a pressure sensor

    Digital Repository Service at National Institute of Oceanography (India)

    Joseph, A.; DeSa, E.J.; Desa, E.; McKeown, J.; Peshwe, V.B.

    for improvement seems to have been a much reduced value of the wave-induced oscillatory boundary layer flow, in the vicinity of the pressure inlet, as compared to the mainstream oscillatory flow. The sensor's performance wa better for the case of waves riding...

  8. Formaldehyde Gas Sensors: A Review

    Directory of Open Access Journals (Sweden)

    Chia-Yen Lee

    2013-04-01

    Full Text Available Many methods based on spectrophotometric, fluorometric, piezoresistive, amperometric or conductive measurements have been proposed for detecting the concentration of formaldehyde in air. However, conventional formaldehyde measurement systems are bulky and expensive and require the services of highly-trained operators. Accordingly, the emergence of sophisticated technologies in recent years has prompted the development of many microscale gaseous formaldehyde detection systems. Besides their compact size, such devices have many other advantages over their macroscale counterparts, including a real-time response, a more straightforward operation, lower power consumption, and the potential for low-cost batch production. This paper commences by providing a high level overview of the formaldehyde gas sensing field and then describes some of the more significant real-time sensors presented in the literature over the past 10 years or so.

  9. Optical Temperature Sensor For Gas Turbines

    Science.gov (United States)

    Mossey, P. W.

    1987-01-01

    New design promises accuracy even in presence of contamination. Improved sensor developed to measure gas temperatures up to 1,700 degree C in gas-turbine engines. Sensor has conical shape for mechanical strengths and optical configuration insensitive to deposits of foreign matter on sides of cone.

  10. Temperature Modulation of a Catalytic Gas Sensor

    Directory of Open Access Journals (Sweden)

    Eike Brauns

    2014-10-01

    Full Text Available The use of catalytic gas sensors usually offers low selectivity, only based on their different sensitivities for various gases due to their different heats of reaction. Furthermore, the identification of the gas present is not possible, which leads to possible misinterpretation of the sensor signals. The use of micro-machined catalytic gas sensors offers great advantages regarding the response time, which allows advanced analysis of the sensor response. By using temperature modulation, additional information about the gas characteristics can be measured and drift effects caused by material shifting or environmental temperature changes can be avoided. In this work a miniaturized catalytic gas sensor which offers a very short response time (<150 ms was developed. Operation with modulated temperature allows analysis of the signal spectrum with advanced information content, based on the Arrhenius approach. Therefore, a high-precise electronic device was developed, since theory shows that harmonics induced by the electronics must be avoided to generate a comprehensible signal.

  11. Development of Sic Gas Sensor Systems

    Science.gov (United States)

    Hunter, G. W.; Neudeck, P. G.; Okojie, R. S.; Beheim, G. M.; Thomas, V.; Chen, L.; Lukco, D.; Liu, C. C.; Ward, B.; Makel, D.

    2002-01-01

    Silicon carbide (SiC) based gas sensors have significant potential to address the gas sensing needs of aerospace applications such as emission monitoring, fuel leak detection, and fire detection. However, in order to reach that potential, a range of technical challenges must be overcome. These challenges go beyond the development of the basic sensor itself and include the need for viable enabling technologies to make a complete gas sensor system: electrical contacts, packaging, and transfer of information from the sensor to the outside world. This paper reviews the status at NASA Glenn Research Center of SiC Schottky diode gas sensor development as well as that of enabling technologies supporting SiC gas sensor system implementation. A vision of a complete high temperature microfabricated SiC gas sensor system is proposed. In the long-term, it is believed that improvements in the SiC semiconductor material itself could have a dramatic effect on the performance of SiC gas sensor systems.

  12. Gas Composition Sensor for Natural Gas and Biogas

    NARCIS (Netherlands)

    Boersma, A.; Sweelsen, J.; Blokland, H.

    2016-01-01

    The calorific value of energetic gasses is an important parameter in the quality assessment of gas steams, and can be calculated from the chemical composition of the gas. An array of capacitive sensor electrodes was developed, each functionalized with a gas responsive coating to measure the

  13. Millimeter-wave sensor image enhancement

    Science.gov (United States)

    Wilson, William J.; Suess, Helmut

    1989-01-01

    Images from an airborne, scanning radiometer operating at a frequency of 98 GHz have been analyzed. The millimeter-wave images were obtained in 1985-1986 using the JPL millimeter-wave imaging sensor. The goal of this study was to enhance the information content of these images and make their interpretation easier. A visual-interpretative approach was used for information extraction from the images. This included application of nonlinear transform techniques for noise reduction and for color, contrast, and edge enhancement. Results of using the techniques on selected millimeter-wave images are discussed.

  14. Airborne Multi-Gas Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Mesa Photonics proposes to develop an Airborne Multi-Gas Sensor (AMUGS) based upon two-tone, frequency modulation spectroscopy (TT-FMS). Mesa Photonics has developed...

  15. Gas Sensors Based on Electrodeposited Polymers

    Directory of Open Access Journals (Sweden)

    Boris Lakard

    2015-07-01

    Full Text Available Electrochemically deposited polymers, also called “synthetic metals”, have emerged as potential candidates for chemical sensing due to their interesting and tunable chemical, electrical, and structural properties. In particular, most of these polymers (including polypyrrole, polyaniline, polythiophene and their derivatives can be used as the sensitive layer of conductimetric gas sensors because of their conducting properties. An important advantage of polymer-based gas sensors is their efficiency at room temperature. This characteristic is interesting since most of the commercially-available sensors, usually based on metal oxides, work at high temperatures (300–400 °C. Consequently, polymer-based gas sensors are playing a growing role in the improvement of public health and environment control because they can lead to gas sensors operating with rapid detection, high sensitivity, small size, and specificity in atmospheric conditions. In this review, the recent advances in electrodeposited polymer-based gas sensors are summarized and discussed. It is shown that the sensing characteristics of electrodeposited polymers can be improved by chemical functionalization, nanostructuration, or mixing with other functional materials to form composites or hybrid materials.

  16. First Fifty Years of Chemoresistive Gas Sensors

    Directory of Open Access Journals (Sweden)

    Giovanni Neri

    2015-01-01

    Full Text Available The first fifty years of chemoresistive sensors for gas detection are here reviewed, focusing on the main scientific and technological innovations that have occurred in the field over the course of these years. A look at advances made in fundamental and applied research and leading to the development of actual high performance chemoresistive devices is presented. The approaches devoted to the synthesis of novel semiconducting materials with unprecedented nanostructure and gas-sensing properties have been also presented. Perspectives on new technologies and future applications of chemoresistive gas sensors have also been highlighted.

  17. A Rapid Process for Fabricating Gas Sensors

    Directory of Open Access Journals (Sweden)

    Chun-Ching Hsiao

    2014-07-01

    Full Text Available Zinc oxide (ZnO is a low-toxicity and environmentally-friendly material applied on devices, sensors or actuators for “green” usage. A porous ZnO film deposited by a rapid process of aerosol deposition (AD was employed as the gas-sensitive material in a CO gas sensor to reduce both manufacturing cost and time, and to further extend the AD application for a large-scale production. The relative resistance change (△R/R of the ZnO gas sensor was used for gas measurement. The fabricated ZnO gas sensors were measured with operating temperatures ranging from 110 °C to 180 °C, and CO concentrations ranging from 100 ppm to 1000 ppm. The sensitivity and the response time presented good performance at increasing operating temperatures and CO concentrations. AD was successfully for applied for making ZnO gas sensors with great potential for achieving high deposition rates at low deposition temperatures, large-scale production and low cost.

  18. Langasite Surface Acoustic Wave Sensors: Fabrication and Testing

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Peng; Greve, David W.; Oppenheim, Irving J.; Chin, Tao-Lun; Malone, Vanessa

    2012-02-01

    We report on the development of harsh-environment surface acoustic wave sensors for wired and wireless operation. Surface acoustic wave devices with an interdigitated transducer emitter and multiple reflectors were fabricated on langasite substrates. Both wired and wireless temperature sensing was demonstrated using radar-mode (pulse) detection. Temperature resolution of better than ±0.5°C was achieved between 200°C and 600°C. Oxygen sensing was achieved by depositing a layer of ZnO on the propagation path. Although the ZnO layer caused additional attenuation of the surface wave, oxygen sensing was accomplished at temperatures up to 700°C. The results indicate that langasite SAW devices are a potential solution for harsh-environment gas and temperature sensing.

  19. Carbon Nanotube Gas Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Sensing gas molecules is critical to environmental monitoring, control of chemical processes, space missions as well as agricultural and medical applications....

  20. Long Wave Infrared Cavity Enhanced Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Taubman, Matthew S.; Scott, David C.; Cannon, Bret D.; Myers, Tanya L.; Munley, John T.; Nguyen, Vinh T.; Schultz, John F.

    2005-12-01

    The principal goal of Pacific Northwest National Laboratory's (PNNL's) long wave infrared (LWIR) cavity enhanced sensor (CES) task is to explore ultra-sensitive spectroscopic chemical sensing techniques and apply them to detecting proliferation of weapons of mass destruction (WMD). Our primary application is detecting signatures of WMD production, but LWIR CES techniques are also capable of detecting chemical weapons. The LWIR CES task is concerned exclusively with developing novel point sensors; stand-off detection is addressed by other PNNL tasks and projects. PNNL's LWIR CES research is distinguished from that done by others by the use quantum cascade lasers (QCLs) as the light source. QCLs are novel devices, and a significant fraction of our research has been devoted to developing the procedures and hardware required to implement them most effectively for chemical sensing. This report details the progress we have made on LWIR CES sensor development.

  1. Ultra-Low-Power MEMS Selective Gas Sensors

    Science.gov (United States)

    Stetter, Joseph

    2012-01-01

    This innovation is a system for gas sensing that includes an ultra-low-power MEMS (microelectromechanical system) gas sensor, combined with unique electronic circuitry and a proprietary algorithm for operating the sensor. The electronics were created from scratch, and represent a novel design capable of low-power operation of the proprietary MEMS gas sensor platform. The algorithm is used to identify a specific target gas in a gas mixture, making the sensor selective to that target gas.

  2. Graphene Based Flexible Gas Sensors

    Science.gov (United States)

    Yi, Congwen

    Graphene is a novel carbon material with great promise for a range of applications due to its electronic and mechanical properties. Its two-dimensional nature translates to a high sensitivity to surface chemical interactions thereby making it an ideal platform for sensors. Graphene's electronic properties are not degraded due to mechanical flexing or strain (Kim, K. S., et al. nature 07719, 2009) offering another advantage for flexible sensors integrated into numerous systems including fabrics, etc. We have demonstrated a graphene NO2 sensor on a solid substrate (100nm SiO2/heavily doped silicon). Three different methods were used to synthesize graphene and the sensor fabrication process was optimized accordingly. Water is used as a controllable p-type dopant in graphene to study the relationship between doping and graphene's response to NO2 . Experimental results show that interface water between graphene and the supporting SiO2 substrate induces higher p-doping in graphene, leading to a higher sensitivity to NO2, consistent with theoretical predications (Zhang, Y. et al., Nanotechnology 20(2009) 185504). We have also demonstrated a flexible and stretchable graphene-based sensor. Few layer graphene, grown on a Ni substrate, is etched and transferred to a highly stretchable polymer substrate (VHB from 3M) with preloaded stress, followed by metal contact formation to construct a flexible, stretchable sensor. With up to 500% deformation caused by compressive stress, graphene still shows stable electrical response to NO2. Our results suggest that higher compressive stress results in smaller sheet resistance and higher sensitivity to NO2. A possible molecular detection sensor utilizing Surface Enhanced Raman Spectrum (SERS) based on a graphene/gallium nanoparticles platform is also studied. By correlating the enhancement of the graphene Raman modes with metal coverage, we propose that the Ga transfers electrons to the graphene creating local regions of enhanced

  3. The development of a surface acoustic wave strain sensor

    OpenAIRE

    Donohoe, Brian

    2011-01-01

    Multi sensors networks are becoming increasingly prevalent in modern engineering applications. In multi sensor networks, wireless sensors are preferred over traditional wired methods. Sensors based upon the surface acoustic wave resonators (SAWR) are often identified as a potential candidate to act as wireless and passive strain sensors. This thesis details the design, fabrication, modelling, calibration and packaging of SAW strain sensors as a general purpose modular strain sensor. The motiv...

  4. A bubble-based microfluidic gas sensor for gas chromatographs.

    Science.gov (United States)

    Bulbul, Ashrafuzzaman; Kim, Hanseup

    2015-01-07

    We report a new proof-of-concept bubble-based gas sensor for a gas chromatography system, which utilizes the unique relationship between the diameters of the produced bubbles with the gas types and mixture ratios as a sensing element. The bubble-based gas sensor consists of gas and liquid channels as well as a nozzle to produce gas bubbles through a micro-structure. It utilizes custom-developed software and an optical camera to statistically analyze the diameters of the produced bubbles in flow. The fabricated gas sensor showed that five types of gases (CO2, He, H2, N2, and CH4) produced (1) unique volumes of 0.44, 0.74, 1.03, 1.28, and 1.42 nL (0%, 68%, 134%, 191%, and 223% higher than that of CO2) and (2) characteristic linear expansion coefficients (slope) of 1.38, 2.93, 3.45, 5.06, and 5.44 nL/(kPa (μL s(-1))(-1)). The gas sensor also demonstrated that (3) different gas mixture ratios of CO2 : N2 (100 : 0, 80 : 20, 50 : 50, 20 : 80 and 0 : 100) generated characteristic bubble diameters of 48.95, 77.99, 71.00, 78.53 and 99.50 μm, resulting in a linear coefficient of 10.26 μm (μL s(-1))(-1). It (4) successfully identified an injection (0.01 μL) of pentane (C5) into a continuous carrier gas stream of helium (He) by monitoring bubble diameters and creating a chromatogram and demonstrated (5) the output stability within only 5.60% variation in 67 tests over a month.

  5. Gas Sensors Based on Molecular Imprinting Technology.

    Science.gov (United States)

    Zhang, Yumin; Zhang, Jin; Liu, Qingju

    2017-07-04

    Molecular imprinting technology (MIT); often described as a method of designing a material to remember a target molecular structure (template); is a technique for the creation of molecularly imprinted polymers (MIPs) with custom-made binding sites complementary to the target molecules in shape; size and functional groups. MIT has been successfully applied to analyze; separate and detect macromolecular organic compounds. Furthermore; it has been increasingly applied in assays of biological macromolecules. Owing to its unique features of structure specificity; predictability; recognition and universal application; there has been exploration of the possible application of MIPs in the field of highly selective gas sensors. In this present study; we outline the recent advances in gas sensors based on MIT; classify and introduce the existing molecularly imprinted gas sensors; summarize their advantages and disadvantages; and analyze further research directions.

  6. Porous Silicon Structures as Optical Gas Sensors

    Directory of Open Access Journals (Sweden)

    Igor A. Levitsky

    2015-08-01

    Full Text Available We present a short review of recent progress in the field of optical gas sensors based on porous silicon (PSi and PSi composites, which are separate from PSi optochemical and biological sensors for a liquid medium. Different periodical and nonperiodical PSi photonic structures (bares, modified by functional groups or infiltrated with sensory polymers are described for gas sensing with an emphasis on the device specificity, sensitivity and stability to the environment. Special attention is paid to multiparametric sensing and sensor array platforms as effective trends for the improvement of analyte classification and quantification. Mechanisms of gas physical and chemical sorption inside PSi mesopores and pores of PSi functional composites are discussed.

  7. Individually Identifiable Surface Acoustic Wave Sensors, Tags and Systems

    Science.gov (United States)

    Hines, Jacqueline H. (Inventor); Solie, Leland P. (Inventor); Tucker, Dana Y. G. (Inventor); Hines, Andrew T. (Inventor)

    2017-01-01

    A surface-launched acoustic wave sensor tag system for remotely sensing and/or providing identification information using sets of surface acoustic wave (SAW) sensor tag devices is characterized by acoustic wave device embodiments that include coding and other diversity techniques to produce groups of sensors that interact minimally, reducing or alleviating code collision problems typical of prior art coded SAW sensors and tags, and specific device embodiments of said coded SAW sensor tags and systems. These sensor/tag devices operate in a system which consists of one or more uniquely identifiable sensor/tag devices and a wireless interrogator. The sensor device incorporates an antenna for receiving incident RF energy and re-radiating the tag identification information and the sensor measured parameter(s). Since there is no power source in or connected to the sensor, it is a passive sensor. The device is wirelessly interrogated by the interrogator.

  8. Surface acoustic wave devices for sensor applications

    Science.gov (United States)

    Bo, Liu; Xiao, Chen; Hualin, Cai; Mohammad, Mohammad Ali; Xiangguang, Tian; Luqi, Tao; Yi, Yang; Tianling, Ren

    2016-02-01

    Surface acoustic wave (SAW) devices have been widely used in different fields and will continue to be of great importance in the foreseeable future. These devices are compact, cost efficient, easy to fabricate, and have a high performance, among other advantages. SAW devices can work as filters, signal processing units, sensors and actuators. They can even work without batteries and operate under harsh environments. In this review, the operating principles of SAW sensors, including temperature sensors, pressure sensors, humidity sensors and biosensors, will be discussed. Several examples and related issues will be presented. Technological trends and future developments will also be discussed. Project supported by the National Natural Science Foundation of China (Nos. 60936002, 61025021, 61434001, 61574083), the State Key Development Program for Basic Research of China (No. 2015CB352100), the National Key Project of Science and Technology (No. 2011ZX02403-002) and the Special Fund for Agroscientific Research in the Public Interest of China (No. 201303107). M.A.M is additionally supported by the Postdoctoral Fellowship (PDF) program of the Natural Sciences and Engineering Research Council (NSERC) of Canada and the China Postdoctoral Science Foundation (CPSF).

  9. Mechanical Drawing of Gas Sensors on Paper

    OpenAIRE

    Mirica, Katherine A.; Weis, Jonathan G.; Schnorr, Jan M.; Esser, Birgit; Swager, Timothy M.

    2012-01-01

    This communication describes a simple solvent-free method for fabricating chemoresistive gas sensors on the surface of paper. The method involves mechanical abrasion of compressed powders of sensing materials on the fibers of cellulose. We illustrate this approach by depositing conductive layers of several forms of carbon (e.g., single-walled carbon nanotubes [SWCNTs], multi-walled carbon nanotubes, and graphite) on the surface of different papers (Figure 1, Figure S1). The resulting sensors ...

  10. Modular Analytical Multicomponent Analysis in Gas Sensor Aarrays

    OpenAIRE

    Theodor Doll; Gerhard Müller; Simon Ahlers; Olaf Kiesewetter; Rüdiger Traute; Ali Chaiyboun

    2006-01-01

    A multi-sensor system is a chemical sensor system which quantitatively and qualitatively records gases with a combination of cross-sensitive gas sensor arrays and pattern recognition software. This paper addresses the issue of data analysis for identification of gases in a gas sensor array. We introduce a software tool for gas sensor array configuration and simulation. It concerns thereby about a modular software package for the acquisition of data of different sensors. A signal evaluation al...

  11. Meso-/Nanoporous Semiconducting Metal Oxides for Gas Sensor Applications

    OpenAIRE

    Nguyen Duc Hoa; Nguyen Van Duy; Sherif A. El-Safty; Nguyen Van Hieu,

    2015-01-01

    Development and/or design of new materials and/or structures for effective gas sensor applications with fast response and high sensitivity, selectivity, and stability are very important issues in the gas sensor technology. This critical review introduces our recent progress in the development of meso-/nanoporous semiconducting metal oxides and their applications to gas sensors. First, the basic concepts of resistive gas sensors and the recent synthesis of meso-/nanoporous metal oxides for gas...

  12. Construction of a Polyaniline Nanofiber Gas Sensor

    Science.gov (United States)

    Virji, Shabnam; Weiller, Bruce H.; Huang, Jiaxing; Blair, Richard; Shepherd, Heather; Faltens, Tanya; Haussmann, Philip C.; Kaner, Richard B.; Tolbert, Sarah H.

    2008-01-01

    The electrical properties of polyaniline changes by orders of magnitude upon exposure to analytes such as acids or bases, making it a useful material for detection of these analytes in the gas phase. The objectives of this lab are to synthesize different diameter polyaniline nanofibers and compare them as sensor materials. In this experiment…

  13. Development of High Temperature Gas Sensor Technology

    Science.gov (United States)

    Hunter, Gary W.; Chen, Liang-Yu; Neudeck, Philip G.; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai; Zhou, Huan-Jun

    1997-01-01

    The measurement of engine emissions is important for their monitoring and control. However, the ability to measure these emissions in-situ is limited. We are developing a family of high temperature gas sensors which are intended to operate in harsh environments such as those in an engine. The development of these sensors is based on progress in two types of technology: (1) The development of SiC-based semiconductor technology; and (2) Improvements in micromachining and microfabrication technology. These technologies are being used to develop point-contact sensors to measure gases which are important in emission control especially hydrogen, hydrocarbons, nitrogen oxides, and oxygen. The purpose of this paper is to discuss the development of this point-contact sensor technology. The detection of each type of gas involves its own challenges in the fields of materials science and fabrication technology. Of particular importance is sensor sensitivity, selectivity, and stability in long-term, high temperature operation. An overview is presented of each sensor type with an evaluation of its stage of development. It is concluded that this technology has significant potential for use in engine applications but further development is necessary.

  14. An electrothermal carbon nanotube gas sensor.

    Science.gov (United States)

    Kawano, Takeshi; Chiamori, Heather C; Suter, Marcel; Zhou, Qin; Sosnowchik, Brian D; Lin, Liwei

    2007-12-01

    We show both gas pressure and species sensing capabilities based on the electrothermal effect of a multiwalled carbon nanotube (MWCNT). Upon exposure to gaseous environments, the resistance of a heated MWCNT is found to change following the conductive heat-transfer variances of gas molecules. To realize this mechanism, a suspended MWCNT is constructed by synthesis and assembly in localized chemical vapor deposition that is accomplished within seconds via real-time electrical feedback control. Vacuum pressure sensitivity and gas species differentiability are observed and analyzed. Such MWCNT electrothermal sensors are compact, fast and reversible in responses, and fully integratable with microelectronics.

  15. Integrated Mirco-Machined Hydrogen Gas Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Frank DiMeoJr. Ing--shin Chen

    2005-12-15

    The widespread use of hydrogen as both an industrial process gas and an energy storage medium requires fast, selective detection of hydrogen gas. This report discusses the development of a new type of solid-state hydrogen gas sensor that couples novel metal hydride thin films with a MEMS (Micro-Electro-Mechanical System) structure known as a micro-hotplate. In this project, Micro-hotplate structures were overcoated with engineered multilayers that serve as the active hydrogen-sensing layer. The change in electrical resistance of these layers when exposed to hydrogen gas was the measured sensor output. This project focused on achieving the following objectives: (1) Demonstrating the capabilities of micro-machined H2 sensors; (2) Developing an understanding of their performance; (3) Critically evaluating the utility and viability of this technology for life safety and process monitoring applications. In order to efficiently achieve these objectives, the following four tasks were identified: (1) Sensor Design and Fabrication; (2) Short Term Response Testing; (3) Long Term Behavior Investigation; (4) Systems Development. Key findings in the project include: The demonstration of sub-second response times to hydrogen; measured sensitivity to hydrogen concentrations below 200 ppm; a dramatic improvement in the sensor fabrication process and increased understanding of the processing properties and performance relationships of the devices; the development of improved sensing multilayers; and the discovery of a novel strain based hydrogen detection mechanism. The results of this program suggest that this hydrogen sensor technology has exceptional potential to meet the stringent demands of life safety applications as hydrogen utilization and infrastructure becomes more prevalent.

  16. Thin films for gas sensors

    Science.gov (United States)

    Pires, Jose Miguel Alves Correia

    Nos ultimos anos tem-se assistido a um aumento dos investimentos na investigacao de novos materiais para aplicacao em sensores. Apesar de ja existir um bom numero de dispositivos explorados comercialmente, muitas vezes, quer devido aos elevados custos de producao, quer devido a uma crescente exigencia do ponto de vista das caracteristicas de funcionamento, continua a ser necessario procurar novos materiais ou novas formas de producao que permitam baixar os custos e melhorar o desempenho dos dispositivos. No campo dos sensores de gases tem-se verificado continuos avancos nos ultimos anos. Continua todavia a ser necessario conhecer melhor, tanto os processos de producao dos materiais, como os mecanismos que regulam a sensibilidade dos dispositivos aos gases, de modo a orientar adequadamente a investigacao dos novos materiais, nomeadamente no que se refere a optimizacao dos parâmetros que nao satisfazem ainda os requisitos do mercado. Um dos materiais que tem mostrado melhores qualidades para aplicacao em sensores de gases de tipo resistivo e o dioxido de estanho. Este material tem sido produzido sob diversas formas e usando diferentes tecnicas, como sejam: sol-gel [1], pulverizacao catodica (sputtering) por magnetrao [2-4], sinterizacao de pos [5, 6], ablacao laser [7] ou RGTO [8]. Os resultados obtidos revelam que as caracteristicas dos dispositivos sao muito dependentes das tecnicas usadas na sua producao. A deposicao usando sputtering reactivo por magnetrao e uma tecnica que permite obter filmes finos de oxido de estanho com diferentes caracteristicas, quer do ponto de vista da estrutura, quer da composicao, e por isso, tambem, com diferentes sensibilidades aos gases. No âmbito deste trabalho, foram produzidos filmes de SnO2 usando sputtering DC reactivo com diferentes condicoes de deposicao. Os substratos usados foram lâminas de vidro e o alvo foi estanho com 99.9% de pureza. Foi estudada a influencia da atmosfera de deposicao, da pressao parcial do O2, da

  17. Optical sensors of gas on the basis of semiconductor sources of infrared emission

    Directory of Open Access Journals (Sweden)

    Kabatsiy V. N.

    2008-08-01

    Full Text Available Various constructions of optic sensors of gas and gas analyzers on their basis with the use of low-powered semiconductor sources of infrared emission for wave-length of 2,5–5,0 mm made on basis of InGaAs/InAs and InAsSbP/InAs heterostructures are worked out. The experimental results demonstrating the ability of application of semiconductor sources of infrared emission in optic sensors for measuring of metan concentration (CH4 and carbon dioxide (CO2 are given. The availability of use of such sensors in the gas analysis equipment of new generation is shown.

  18. New Vision Sensor to Measure Gas Pressure

    Directory of Open Access Journals (Sweden)

    Murawski Krzysztof

    2015-06-01

    Full Text Available The paper presents the construction and operation of a video sensor developed for video-manometer. In the publication the use of video-manometer for measuring gas pressure is presented. A characteristic feature of the device is pressure measurement based on diaphragm deformation and digital image processing. Presented measuring technique eliminates restrictions in the construction of the measuring apparatus arising from non-linear nature of diaphragm deformation. It also allows performing measurements of gas pressure, also of explosive gas, providing galvanic isolation between the factor measured and the measuring device. The paper presents the results of video-manometer calibration and measurements taken during the laboratory tests. It has been shown that the developed video-manometer, that is equipped with a flat silicone diaphragm, allows measuring the gas pressure in the range of 0 – 100 mbar with an error less than 2 %. In the experiments the CO2 pressure was measured.

  19. Modular Analytical Multicomponent Analysis in Gas Sensor Aarrays

    Science.gov (United States)

    Chaiyboun, Ali; Traute, Rüdiger; Kiesewetter, Olaf; Ahlers, Simon; Müller, Gerhard; Doll, Theodor

    2006-01-01

    A multi-sensor system is a chemical sensor system which quantitatively and qualitatively records gases with a combination of cross-sensitive gas sensor arrays and pattern recognition software. This paper addresses the issue of data analysis for identification of gases in a gas sensor array. We introduce a software tool for gas sensor array configuration and simulation. It concerns thereby about a modular software package for the acquisition of data of different sensors. A signal evaluation algorithm referred to as matrix method was used specifically for the software tool. This matrix method computes the gas concentrations from the signals of a sensor array. The software tool was used for the simulation of an array of five sensors to determine gas concentration of CH4, NH3, H2, CO and C2H5OH. The results of the present simulated sensor array indicate that the software tool is capable of the following: (a) identify a gas independently of its concentration; (b) estimate the concentration of the gas, even if the system was not previously exposed to this concentration; (c) tell when a gas concentration exceeds a certain value. A gas sensor data base was build for the configuration of the software. With the data base one can create, generate and manage scenarios and source files for the simulation. With the gas sensor data base and the simulation software an on-line Web-based version was developed, with which the user can configure and simulate sensor arrays on-line.

  20. Wireless Passive Strain Sensor Based on Surface Acoustic Wave Devices

    OpenAIRE

    Nomura, T.; Kawasaki, K.; Saitoh, A

    2008-01-01

    Surface acoustic wave (SAW) devices offer many attractive features for applications as chemical and physical sensors. In this paper, a novel SAW strain sensor that employs SAW delay lines has been designed. Two crossed delay lines were used to measure the two-dimensional strain. A wireless sensing system is also proposed for effective operation of the strain sensor. In addition, an electronic system for accurately measuring the phase characteristics of the signal wave from the passive strain ...

  1. Sol-Gel Thin Films for Plasmonic Gas Sensors

    Directory of Open Access Journals (Sweden)

    Enrico Della Gaspera

    2015-07-01

    Full Text Available Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform. Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors. In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors.

  2. Gas Main Sensor and Communications Network System

    Energy Technology Data Exchange (ETDEWEB)

    Hagen Schempf

    2006-05-31

    Automatika, Inc. was contracted by the Department of Energy (DOE) and with co-funding from the Northeast Gas Association (NGA), to develop an in-pipe natural gas prototype measurement and wireless communications system for assessing and monitoring distribution networks. This projected was completed in April 2006, and culminated in the installation of more than 2 dozen GasNet nodes in both low- and high-pressure cast-iron and steel mains owned by multiple utilities in the northeastern US. Utilities are currently logging data (off-line) and monitoring data in real time from single and multiple networked sensors over cellular networks and collecting data using wireless bluetooth PDA systems. The system was designed to be modular, using in-pipe sensor-wands capable of measuring, flow, pressure, temperature, water-content and vibration. Internal antennae allowed for the use of the pipe-internals as a waveguide for setting up a sensor network to collect data from multiple nodes simultaneously. Sensor nodes were designed to be installed with low- and no-blow techniques and tools. Using a multi-drop bus technique with a custom protocol, all electronics were designed to be buriable and allow for on-board data-collection (SD-card), wireless relaying and cellular network forwarding. Installation options afforded by the design included direct-burial and external polemounted variants. Power was provided by one or more batteries, direct AC-power (Class I Div.2) and solar-array. The utilities are currently in a data-collection phase and intend to use the collected (and processed) data to make capital improvement decisions, compare it to Stoner model predictions and evaluate the use of such a system for future expansion, technology-improvement and commercialization starting later in 2006.

  3. Compact portable QEPAS multi-gas sensor

    Science.gov (United States)

    Dong, Lei; Kosterev, Anatoliy A.; Thomazy, David; Tittel, Frank K.

    2011-01-01

    A quartz-enhanced photoacoustic spectroscopy (QEPAS) based multi-gas sensor was developed to quantify concentrations of carbon monoxide (CO), hydrogen cyanide (HCN), hydrogen chloride (HCl), and carbon dioxide (CO2) in ambient air. The sensor consists of a compact package of dimensions 25cm x 25cm x 10cm and was designed to operate at atmospheric pressure. The HCN, CO2, and HCl measurement channels are based on cw, C-band telecommunication-style packaged, fiber-coupled diode lasers, while the CO channel uses a TO can-packaged Sb diode laser as an excitation source. Moreover, the sensor incorporates rechargeable batteries and can operate on batteries for at least 8 hours. It can also operate autonomously or interact with another device (such as a computer) via a RS232 serial port. Trace gas detection limits of 7.74ppm at 4288.29cm-1 for CO, 450ppb at 6539.11 cm-1 for HCN, 1.48ppm at 5739.26 cm-1 for HCl and 97ppm at 6361.25 cm-1 for CO2 for a 1sec average time, were demonstrated.

  4. Modular Analytical Multicomponent Analysis in Gas Sensor Aarrays

    Directory of Open Access Journals (Sweden)

    Theodor Doll

    2006-04-01

    Full Text Available A multi-sensor system is a chemical sensor system which quantitatively andqualitatively records gases with a combination of cross-sensitive gas sensor arrays andpattern recognition software. This paper addresses the issue of data analysis foridentification of gases in a gas sensor array. We introduce a software tool for gas sensorarray configuration and simulation. It concerns thereby about a modular software packagefor the acquisition of data of different sensors. A signal evaluation algorithm referred to asmatrix method was used specifically for the software tool. This matrix method computes thegas concentrations from the signals of a sensor array. The software tool was used for thesimulation of an array of five sensors to determine gas concentration of CH4, NH3, H2, COand C2H5OH. The results of the present simulated sensor array indicate that the softwaretool is capable of the following: (a identify a gas independently of its concentration; (bestimate the concentration of the gas, even if the system was not previously exposed to thisconcentration; (c tell when a gas concentration exceeds a certain value. A gas sensor database was build for the configuration of the software. With the data base one can create,generate and manage scenarios and source files for the simulation. With the gas sensor database and the simulation software an on-line Web-based version was developed, with whichthe user can configure and simulate sensor arrays on-line.

  5. Conductive Polymer Nanowire Gas Sensor Fabricated by Nanoscale Soft Lithography.

    Science.gov (United States)

    Tang, Ning; Jiang, Yang; Qu, Hemi; Duan, Xuexin

    2017-10-02

    Resistive devices composed of one dimensional nanostructures are promising candidate for next generation gas sensors. However, the large-scale fabrication of nanowires is still a challenge, restricting the commercialization of such type of devices. Here, we reported a highly efficient and facile approach to fabricate poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) nanowire chemiresistive type of gas sensor by nanoscale soft lithography. Well-defined sub-100 nm nanowires are fabricated on silicon substrate which facilitates the device integration. The nanowire chemiresistive gas sensor is demonstrated for NH3 and NO2 detection at room-temperature and shows a limit of detection at ppb level which is compatible with nanoscale PEDOT:PSS gas sensors fabricated with conventional lithography technique. In comparison with PEDOT:PSS thin film gas sensor, the nanowire gas sensor exhibits a higher sensitivity and much faster response to gas molecules. © 2017 IOP Publishing Ltd.

  6. Conductive polymer nanowire gas sensor fabricated by nanoscale soft lithography

    Science.gov (United States)

    Tang, Ning; Jiang, Yang; Qu, Hemi; Duan, Xuexin

    2017-12-01

    Resistive devices composed of one-dimensional nanostructures are promising candidates for the next generation of gas sensors. However, the large-scale fabrication of nanowires is still challenging, which restricts the commercialization of such devices. Here, we report a highly efficient and facile approach to fabricating poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) nanowire chemiresistive gas sensors by nanoscale soft lithography. Well-defined sub-100 nm nanowires are fabricated on silicon substrate, which facilitates device integration. The nanowire chemiresistive gas sensor is demonstrated for NH3 and NO2 detection at room temperature and shows a limit of detection at ppb level, which is compatible with nanoscale PEDOT:PSS gas sensors fabricated with the conventional lithography technique. In comparison with PEDOT:PSS thin-film gas sensors, the nanowire gas sensor exhibits higher sensitivity and a much faster response to gas molecules.

  7. Optimization of Surface Acoustic Wave-Based Rate Sensors

    Directory of Open Access Journals (Sweden)

    Fangqian Xu

    2015-10-01

    Full Text Available The optimization of an surface acoustic wave (SAW-based rate sensor incorporating metallic dot arrays was performed by using the approach of partial-wave analysis in layered media. The optimal sensor chip designs, including the material choice of piezoelectric crystals and metallic dots, dot thickness, and sensor operation frequency were determined theoretically. The theoretical predictions were confirmed experimentally by using the developed SAW sensor composed of differential delay line-oscillators and a metallic dot array deposited along the acoustic wave propagation path of the SAW delay lines. A significant improvement in sensor sensitivity was achieved in the case of 128° YX LiNbO3, and a thicker Au dot array, and low operation frequency were used to structure the sensor.

  8. Investigation of competitive and thermal-wave effects in photoelectric H{sub 2} sensors

    Energy Technology Data Exchange (ETDEWEB)

    Mandelis, A.; Wagner, R.E. [Toronto Univ., ON (Canada). Dept. of Mechanical Engineering

    1994-12-31

    Detailed experimental comparisons of the two competing signal generation modes in photopyroelectric gas sensors, i.e. the purely chemical and the purely thermal-wave mode, were performed. The purpose was to selectively isolate one or the other detection mode, through total or partial annulment of the effect of the other, using several instrumentation techniques. Competing effects on hydrogen gas concentration and flow-rate, signal optimization with respect to one or the other mode, and new progress on the mechanistic aspects of the sensor signal generation were also discussed. Effectiveness of the photopyroelectric hydrogen sensor was demonstrated. The sensor was more sensitive to optical changes of Pd than sensors which measure the reflectance of a Pd film. It was suggested that judicious choice of the excitation wavelength and the Pd-film thickness would result in detection limits of about 0.1% in air. 13 refs., 6 figs.

  9. Electrochemical high-temperature gas sensors

    Science.gov (United States)

    Saruhan, B.; Stranzenbach, M.; Yüce, A.; Gönüllü, Y.

    2012-06-01

    Combustion produced common air pollutant, NOx associates with greenhouse effects. Its high temperature detection is essential for protection of nature. Component-integration capable high-temperature sensors enable the control of combustion products. The requirements are quantitative detection of total NOx and high selectivity at temperatures above 500°C. This study reports various approaches to detect NO and NO2 selectively under lean and humid conditions at temperatures from 300°C to 800°C. All tested electrochemical sensors were fabricated in planar design to enable componentintegration. We suggest first an impedance-metric gas sensor for total NOx-detection consisting of NiO- or NiCr2O4-SE and PYSZ-electrolyte. The electrolyte-layer is about 200μm thickness and constructed of quasi-single crystalline columns. The sensing-electrode (SE) is magnetron sputtered thin-layers of NiO or NiCr2O4. Sensor sensitivity for detection of total NOx has been measured by applying impedance analysis. The cross-sensitivity to other emission gases such as CO, CO2, CH4 and oxygen (5 vol.%) has been determined under 0-1000ppm NO. Sensor maintains its high sensitivity at temperatures up to 550°C and 600°C, depending on the sensing-electrode. NiO-SE yields better selectivity to NO in the presence of oxygen and have shorter response times comparing to NiCr2O4-SE. For higher temperature NO2-sensing capability, a resistive DC-sensor having Al-doped TiO2-sensing layers has been employed. Sensor-sensitivity towards NO2 and cross-sensitivity to CO has been determined in the presence of H2O at temperatures 600°C and 800°C. NO2 concentrations varying from 25 to 100ppm and CO concentrations from 25 to 75ppm can be detected. By nano-tubular structuring of TiO2, NO2 sensitivity of the sensor was increased.

  10. Conductivity modeling of gas sensors based on copper ...

    African Journals Online (AJOL)

    application, the use of chemical gas sensors constitutes a very attractive alternative [2]. Amongst all ... of our gas sensor device consists in a copper phthalocyanine (CuPc) thin films of 300 nm prepared by physical vapor ..... thin layer, modeling the law of conductivity evolution versus the concentration of the doping gas at ...

  11. Wireless Passive Strain Sensor Based on Surface Acoustic Wave Devices

    Directory of Open Access Journals (Sweden)

    T. Nomura

    2008-04-01

    Full Text Available Surface acoustic wave (SAW devices offer many attractive features for applications as chemical and physical sensors. In this paper, a novel SAW strain sensor that employs SAW delay lines has been designed. Two crossed delay lines were used to measure the two-dimensional strain. A wireless sensing system is also proposed for effective operation of the strain sensor. In addition, an electronic system for accurately measuring the phase characteristics of the signal wave from the passive strain sensor is proposed.

  12. Large-Scale Integrated Carbon Nanotube Gas Sensors

    OpenAIRE

    Joondong Kim

    2012-01-01

    Carbon nanotube (CNT) is a promising one-dimensional nanostructure for various nanoscale electronics. Additionally, nanostructures would provide a significant large surface area at a fixed volume, which is an advantage for high-responsive gas sensors. However, the difficulty in fabrication processes limits the CNT gas sensors for the large-scale production. We review the viable scheme for large-area application including the CNT gas sensor fabrication and reaction mechanism with a practical d...

  13. Gas Sensors Based on Polymer Field-Effect Transistors

    OpenAIRE

    Aifeng Lv; Yong Pan; Lifeng Chi

    2017-01-01

    This review focuses on polymer field-effect transistor (PFET) based gas sensor with polymer as the sensing layer, which interacts with gas analyte and thus induces the change of source-drain current (?I SD). Dependent on the sensing layer which can be semiconducting polymer, dielectric layer or conducting polymer gate, the PFET sensors can be subdivided into three types. For each type of sensor, we present the molecular structure of sensing polymer, the gas analyte and the sensing performance...

  14. Metal/Metal-Oxide Nanoclusters for Gas Sensor Applications

    OpenAIRE

    Ayesh, Ahmad I.

    2016-01-01

    The development of gas sensors that are based on metal/metal-oxide nanoclusters has attracted intensive research interest in the last years. Nanoclusters are suitable candidates for gas sensor applications because of their large surface-to-volume ratio that can be utilized for selective and rapid detection of various gaseous species with low-power consuming electronics. Herein, nanoclusters are used as building blocks for the construction of gas sensor where the electrical conductivity of the...

  15. Large-Scale Integrated Carbon Nanotube Gas Sensors

    Directory of Open Access Journals (Sweden)

    Joondong Kim

    2012-01-01

    Full Text Available Carbon nanotube (CNT is a promising one-dimensional nanostructure for various nanoscale electronics. Additionally, nanostructures would provide a significant large surface area at a fixed volume, which is an advantage for high-responsive gas sensors. However, the difficulty in fabrication processes limits the CNT gas sensors for the large-scale production. We review the viable scheme for large-area application including the CNT gas sensor fabrication and reaction mechanism with a practical demonstration.

  16. Palladium-nanoparticle-coated carbon nanotube gas sensor

    Science.gov (United States)

    Han, Maeum; Jung, Daewoong; Lee, Gil S.

    2014-08-01

    Flexible hydrogen gas sensors were fabricated using multi-walled carbon nanotubes (MWCNTs) decorated with Pd nanoparticles for the detection of H2 gas at room temperature. A comparative gas-sensing study was carried out on both the Pd-nanoparticles-decorated and undecorated MWCNT sheets in order to examine the effect of Pd nanoparticles on the gas-sensing performances at room temperature. Experimental results showed that the MWCNTs/Pd sensor exhibited fast response and recovery as well as high sensitivity compared with the pure MWCNT sensor. The improved sensing properties of this sensor were attributed to the spillover effect of Pd nanoparticles and the highly conductive MWCNT sheet.

  17. A SF6 gas sensor using a dual track SAW device based on multi-wall carbon nanotubes

    Science.gov (United States)

    Wen, Changbao; Zhu, Changchun; Ju, Yongfeng; Liu, Li; Li, Wanlin; Yan, Dong; Xu, Hongke; Qiu, Yanzhang

    2011-03-01

    In this paper, we propose a sulfur hexafluoride (SF6) gas sensor using a dual track surface acoustic wave (SAW) device based on multi-wall carbon nanotubes (MWCNTs). The sensor consists of a dual track SAW device and MWCNT film sensitive to SF6 gas. The measurement acoustic track of the sensor is coated with an MWCNT film treated by an acid process which selectively absorbs SF6 gas, while the reference acoustic track is uncoated. Experimental results confirm that the SF6 gas sensor using a dual track SAW device based on multi-wall CNTs has good response characteristics to different concentrations of SF6 gas from 0.5 to 20 ppm. The sensor has good linearity and reproducibility, and its sensitivity is approximately 7.4 kHz ppm-1. Furthermore, the sensor has a smaller cross-sensitivity for SO2 and HF.

  18. Modeling of a Surface Acoustic Wave Strain Sensor

    Science.gov (United States)

    Wilson, W. C.; Atkinson, Gary M.

    2010-01-01

    NASA Langley Research Center is investigating Surface Acoustic Wave (SAW) sensor technology for harsh environments aimed at aerospace applications. To aid in development of sensors a model of a SAW strain sensor has been developed. The new model extends the modified matrix method to include the response of Orthogonal Frequency Coded (OFC) reflectors and the response of SAW devices to strain. These results show that the model accurately captures the strain response of a SAW sensor on a Langasite substrate. The results of the model of a SAW Strain Sensor on Langasite are presented

  19. Circuit Design of Surface Acoustic Wave Based Micro Force Sensor

    Directory of Open Access Journals (Sweden)

    Yuanyuan Li

    2014-01-01

    Full Text Available Pressure sensors are commonly used in industrial production and mechanical system. However, resistance strain, piezoresistive sensor, and ceramic capacitive pressure sensors possess limitations, especially in micro force measurement. A surface acoustic wave (SAW based micro force sensor is designed in this paper, which is based on the theories of wavelet transform, SAW detection, and pierce oscillator circuits. Using lithium niobate as the basal material, a mathematical model is established to analyze the frequency, and a peripheral circuit is designed to measure the micro force. The SAW based micro force sensor is tested to show the reasonable design of detection circuit and the stability of frequency and amplitude.

  20. Zirconia-based solid state chemical gas sensors

    CERN Document Server

    Zhuiykov, S

    2000-01-01

    This paper presents an overview of chemical gas sensors, based on solid state technology, that are sensitive to environmental gases, such as O sub 2 , SO sub x , NO sub x , CO sub 2 and hydrocarbons. The paper is focussed on performance of electrochemical gas sensors that are based on zirconia as a solid electrolyte. The paper considers sensor structures and selection of electrode materials. Impact of interfaces on sensor performance is discussed. This paper also provides a brief overview of electrochemical properties of zirconia and their effect on sensor performance. Impact of auxiliary materials on sensors performance characteristics, such as sensitivity, selectivity, response time and recovery time, is also discussed. Dual gas sensors that can be applied for simultaneous monitoring of the concentration of both oxygen and other gas phase components, are briefly considered

  1. Study on Hydrogen Gas concentration to Voltage and Resistance using Semiconductor Hydrogen Gas Sensor

    Directory of Open Access Journals (Sweden)

    Ahmad Arif Hasibuan

    2016-10-01

    Full Text Available Study on hydrogen gas concentration to changes in voltage and resistance using semiconductor hydrogen gas sensor has been done. The system which has been designed will measure any changes in the voltage and resistance of the sensor automatically when the sensor is given a variation of concentration on hydrogen gas. On the condition of gas with low concentration, the sensor output voltage obtained worth 0:08 Volt and the sensor resistance value of 180 KΩ. On the increase in gas concentration causes an increase in sensor output voltage and a decrease in the value of resistance Studi tentang pengaruh konsentrasi kadar gas hidrogen terhadap perubahan tegangan dan resistansi menggunakan sensor gas hidrogen berbasis semikonduktor telah berhasil dilakukan. Sistem yang telah dirancang akan mengukur setiap perubahan tegangan dan resistansi secara digital pada sensor saat diberikan variasi terhadap konsentrasi kadar gas hidrogen. Pada kondisi gas dengan konsentrasi rendah diperoleh tegangan output sensor senilai 0.08 Volt dan nilai resistansi sensor sebesar 180 KΩ. Pada peningkatan konsentrasi gas menyebabkan peningkatan tegangan output sensor dan sebaliknya terjadi penurunan pada nilai resistansi

  2. Elastic Wave Measurement Using a MEMS AE Sensor

    Directory of Open Access Journals (Sweden)

    Takahiro Omori

    2017-07-01

    Full Text Available In recent years, with the continuing progress of aging social infrastructures such as bridges and tunnels, there has been high demand for the assessment of deterioration of their performance and conditions. Since current inspection methods for those structures have mainly relied on human resources, it is important to reduce their increasing maintenance cost. One of the key methods for achieving effective maintenance without expensive human costs is to use sensors to discriminate between healthy and unhealthy conditions. In this paper, a MEMS (micro electro mechanical systems wideband frequency sensor, which is referred to as a super acoustic (SA sensor, is evaluated through the pencil lead break (PLB test. Due to its wideband frequency characteristics, the SA sensor is expected to be a promising alternative to the existing vibration sensors, including acoustic emission (AE sensors. Several PLB signals were generated on an aluminum plate (5 mm thick, and propagating Lamb waves were detected by both AE and SA sensors. SA sensors were able to identify the location of PLB sources on the plate by measuring time differences between each sensor. By comparing the wave spectrums of both the AE and SA sensors analyzed by wavelet transform, the applicability of SA sensor for AE measurement is verified.

  3. Wave Monitoring with Wireless Sensor Networks

    NARCIS (Netherlands)

    Marin Perianu, Mihai; Chatterjea, Supriyo; Marin Perianu, Raluca; Bosch, S.; Dulman, S.O.; Kininmonth, Stuart; Havinga, Paul J.M.

    2008-01-01

    Real-time collection of wave information is required for short and long term investigations of natural coastal processes. Current wave monitoring techniques use only point-measurements, which are practical where the bathymetry is relatively uniform. We propose a wave monitoring method that is

  4. Radar and Laser Sensors for High Frequency Ocean Wave Measurement.

    Science.gov (United States)

    Kennedy, C. R.

    2016-02-01

    Experimental measurement of air-sea fluxes invariably take place using shipbourne instrumentation and simultaneous measurement of wave height and direction is desired. A number of researchers have shown that range measuring sensors combined with inertial motion compensation can be successful on board stationary or very slowly moving ships. In order to measure wave characteristics from ships moving at moderate to full speed the sensors are required to operate at higher frequency so as to overcome the Doppler shift caused by ship motion. This work presents results from some preliminary testing of laser, radar and ultrasonic range sensors in the laboratory and on board ship. The characteristics of the individual sensors are discussed and comparison of the wave spectra produced by each is presented.

  5. Potential use of gas sensors in beef manure nutrient content ...

    African Journals Online (AJOL)

    The purpose of this study was to develop a gas sensor array to estimate the manure nutrient contents. Three metal-oxide gas sensors including methane, ammonia and hydrogen sulfide were used. Forty manure samples were collected from four beef operations in Southwest North Dakota. Manure samples were sent to be ...

  6. Potential use of gas sensors in beef manure nutrient content ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-06-17

    Jun 17, 2009 ... between sensor array readings and the lab results. The sensor array was able to estimate manure N, P, and K with correlation coefficients of 0.80, 0.76 and 0.70, respectively. Key words: Waste management, animal manure, crop nutrient, gas sensors. INTRODUCTION. Livestock production is a major ...

  7. Advancement of Miniature Optic Gas Sensor (MOGS) Probe Technology

    Science.gov (United States)

    Chullen, Cinda

    2015-01-01

    Advancement of Miniature Optic Gas Sensor (MOGS) Probe Technology" project will investigate newly developed optic gas sensors delivered from a Small Business Innovative Research (SBIR) Phase II effort. A ventilation test rig will be designed and fabricated to test the sensors while integrated with a Suited Manikin Test Apparatus (SMTA). Once the sensors are integrated, a series of test points will be completed to verify that the sensors can withstand Advanced Suit Portable Life Support System (PLSS) environments and associated human metabolic profiles for changes in pressure and levels of Oxygen (ppO2), carbon dioxide (ppCO2), and humidity (ppH2O).

  8. Temperature control of micro heater using Pt thin film temperature sensor embedded in micro gas sensor

    Science.gov (United States)

    Kang, Jun-gu; Park, Joon-Shik; Park, Kwang-Bum; Shin, Junho; Lee, Eung-An; Noh, Sangsoo; Lee, Hoo-Jeong

    2017-12-01

    Pt thin film temperature sensors (Pt T sensors) are embedded in micro gas sensors to measure and control the working temperature. We characterized electrical resistances of Pt T sensors and micro heaters with temperature changing in the oven and by Joule heating. In order to enhance the accuracy of temperature measurement by the Pt T sensors, we investigated the correlation among the Pt T sensor, micro heater, and the working temperature, which was linear proportional relation expressed as the equation: T2 = 6.466R1-642.8, where T2 = temperature of the Pt micro heater and R1 = the electrical resistance of the Pt T sensor. As the error by physically separated gap between Pt T sensor and micro heater calibrated, measuring and controlling temperature of micro heater in micro gas sensors were possible through the Pt T sensors. For the practical use of Pt T sensor in micro gas sensor, the gas sensing properties of fabricated micro gas sensors to 25 ppm CO and 1 ppm HCHO gases were characterized.

  9. Simulation and Fabrication of SAW-Based Gas Sensor with Modified Surface State of Active Layer and Electrode Orientation for Enhanced H2 Gas Sensing

    Science.gov (United States)

    Hasan, Md. Nazibul; Maity, Santanu; Sarkar, Argha; Bhunia, Chandan Tilak; Acharjee, Debabrata; Joseph, Aneesh M.

    2017-02-01

    The design, analysis, optimization, and fabrication of layered and nanostructure-based surface acoustic wave (SAW) gas sensors are presented. A lithium niobate and zinc oxide (ZnO) nano multilayer structure is proposed to enhance the sensitivity of the SAW-based gas sensor. Different materials are considered for the intermediate layer in the design for optimization purposes. The sensitivity of the sensor could be improved due to increased active surface area obtained by varying the aspect ratio of the nanorods, the thickness of the intermediate layer, and the gap between the electrodes. The total displacement and frequency shift of the device were significantly improved. Overall, the mechanically engineered surface-based (nanorod) SAW gas sensor offered better sensing response than the layered SAW gas sensor in terms of sensitivity performance.

  10. GAS MAIN SENSOR AND COMMUNICATIONS NETWORK SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Hagen Schempf

    2004-09-30

    Automatika, Inc. was contracted by the Department of Energy (DOE) and with co-funding from the New York Gas Group (NYGAS), to develop an in-pipe natural gas prototype measurement and wireless communications system for assessing and monitoring distribution networks. In Phase II of this three-phase program, an improved prototype system was built for low-pressure cast-iron and high-pressure steel (including a no-blow installation system) mains and tested in a serial-network configuration in a live network in Long Island with the support of Keyspan Energy, Inc. The experiment was carried out in several open-hole excavations over a multi-day period. The prototype units (3 total) combined sensors capable of monitoring pressure, flow, humidity, temperature and vibration, which were sampled and combined in data-packages in an in-pipe master-repeater-slave configuration in serial or ladder-network arrangements. It was verified that the system was capable of performing all data-sampling, data-storage and collection as expected, yielding interesting results as to flow-dynamics and vibration-detection. Wireless in-pipe communications were shown to be feasible and the system was demonstrated to run off in-ground battery- and above-ground solar power. The remote datalogger access and storage-card features were demonstrated and used to log and post-process system data. Real-time data-display on an updated Phase-I GUI was used for in-field demonstration and troubleshooting.

  11. Metal/Metal-Oxide Nanoclusters for Gas Sensor Applications

    Directory of Open Access Journals (Sweden)

    Ahmad I. Ayesh

    2016-01-01

    Full Text Available The development of gas sensors that are based on metal/metal-oxide nanoclusters has attracted intensive research interest in the last years. Nanoclusters are suitable candidates for gas sensor applications because of their large surface-to-volume ratio that can be utilized for selective and rapid detection of various gaseous species with low-power consuming electronics. Herein, nanoclusters are used as building blocks for the construction of gas sensor where the electrical conductivity of the nanoclusters changes dramatically upon exposure to the target gas. In this review, recent progress in the fabrication of size-selected metallic nanoclusters and their utilization for gas sensor applications is presented. Special focus will be given to the enhancement of the sensing performance through the rational functionalization and utilization of different nanocluster materials.

  12. Meso-/Nanoporous Semiconducting Metal Oxides for Gas Sensor Applications

    Directory of Open Access Journals (Sweden)

    Nguyen Duc Hoa

    2015-01-01

    Full Text Available Development and/or design of new materials and/or structures for effective gas sensor applications with fast response and high sensitivity, selectivity, and stability are very important issues in the gas sensor technology. This critical review introduces our recent progress in the development of meso-/nanoporous semiconducting metal oxides and their applications to gas sensors. First, the basic concepts of resistive gas sensors and the recent synthesis of meso-/nanoporous metal oxides for gas sensor applications are introduced. The advantages of meso-/nanoporous metal oxides are also presented, taking into account the crystallinity and ordered/disordered porous structures. Second, the synthesis methods of meso-/nanoporous metal oxides including the soft-template, hard-template, and temple-free methods are introduced, in which the advantages and disadvantages of each synthetic method are figured out. Third, the applications of meso-/nanoporous metal oxides as gas sensors are presented. The gas nanosensors are designed based on meso-/nanoporous metal oxides for effective detection of toxic gases. The sensitivity, selectivity, and stability of the meso-/nanoporous gas nanosensors are also discussed. Finally, some conclusions and an outlook are presented.

  13. Surface Acoustic WaveAmmonia Sensors Based on ST-cut Quartz under Periodic Al Structure

    Directory of Open Access Journals (Sweden)

    Ming-Yau Su

    2009-02-01

    Full Text Available Surface acoustic wave (SAW devices are key components for sensing applications. SAW propagation under a periodic grating was investigated in this work. The theoretical method used here is the space harmonic method. We also applied the results of SAW propagation studied in this work to design a two-port resonator with an Al grating on ST-cut quartz. The measured frequency responses of the resonator were similar to the simulation ones. Then, the chemical interface of polyaniline/WO3 composites was coated on the SAW sensor for ammonia detection. The SAW sensor responded to ammonia gas and could be regenerated using dry nitrogen.

  14. Studies of CNT and Polymer Based Gas Sensor

    Directory of Open Access Journals (Sweden)

    Monika JOSHI

    2010-11-01

    Full Text Available Gas sensors of different types are being used for environmental monitoring. Among all the gas sensors CNT based gas sensors are widely used .The gas sensors consist of polymer- CNT as an active layer, where the adsorption of gas molecules leads to a large change in its electrical resistivity. They have merits of being low cost, good sensitivity, and convenient to measure response (a simple change in resistance. In the present investigation purified multi wall carbon nanotubes (MWNT have been used as a sensing material for detecting ammonia gas. In this work, a thick film of Carbon nanotube -polymer was prepared and painted over ring types of electrodes. Carbon nanotubes are highly efficient gas adsorption agents due to their high surface-to-volume ratio. In order to improve the efficiency of the sensor CNT-polyvinyl pyroiodine composite film was prepared. The gas sensing properties of the composite film for ammonia vapor were tested by measuring the resistance during a span of 720 seconds at an interval of 10 seconds each. A composite polymer CNT film showed a high response and rapid sensing to the test gas. The observations were taken by varying the concentration of ammonia at room temperature. An increase in resistance has been observed with the increase in time. The sensing mechanism of the composite has been explained on the basis of volume expansion and polar interaction of various vapors on the carbon nanotubes surface.

  15. Design and characterization of a Raman-scattering-based sensor system for temporally resolved gas analysis and its application in a gas turbine power plant

    Science.gov (United States)

    Kiefer, J.; Seeger, T.; Steuer, S.; Schorsch, S.; Weikl, M. C.; Leipertz, A.

    2008-08-01

    A sensor system for fast gas composition analysis is presented. Using linear Raman scattering the simultaneous detection of virtually all components of fuel gas mixtures such as natural gas and biogas can be achieved. The system consists of commercially available hardware components, in detail a frequency doubled continuous wave laser at 532 nm and a compact spectrometer with an embedded charge coupled device chip. For the evaluation of the Raman spectra a fast software module based on a contour fit algorithm is developed. Moreover, modules for controlling the hardware components are implemented in the sensor software ensuring simple operability of the entire system. In this paper the sensor is characterized in terms of, e.g., accuracy, reproducibility, detection limits and temporal performance. Finally its application for natural gas analysis in a gas turbine power plant is demonstrated, and the results obtained are compared to gas chromatography results.

  16. Gas Sensors Based on Polymer Field-Effect Transistors

    Science.gov (United States)

    Lv, Aifeng; Pan, Yong; Chi, Lifeng

    2017-01-01

    This review focuses on polymer field-effect transistor (PFET) based gas sensor with polymer as the sensing layer, which interacts with gas analyte and thus induces the change of source-drain current (ΔISD). Dependent on the sensing layer which can be semiconducting polymer, dielectric layer or conducting polymer gate, the PFET sensors can be subdivided into three types. For each type of sensor, we present the molecular structure of sensing polymer, the gas analyte and the sensing performance. Most importantly, we summarize various analyte–polymer interactions, which help to understand the sensing mechanism in the PFET sensors and can provide possible approaches for the sensor fabrication in the future. PMID:28117760

  17. Gas Sensors Based on Polymer Field-Effect Transistors

    Directory of Open Access Journals (Sweden)

    Aifeng Lv

    2017-01-01

    Full Text Available This review focuses on polymer field-effect transistor (PFET based gas sensor with polymer as the sensing layer, which interacts with gas analyte and thus induces the change of source-drain current (ΔISD. Dependent on the sensing layer which can be semiconducting polymer, dielectric layer or conducting polymer gate, the PFET sensors can be subdivided into three types. For each type of sensor, we present the molecular structure of sensing polymer, the gas analyte and the sensing performance. Most importantly, we summarize various analyte–polymer interactions, which help to understand the sensing mechanism in the PFET sensors and can provide possible approaches for the sensor fabrication in the future.

  18. Detecting high-frequency gravitational waves with optically levitated sensors.

    Science.gov (United States)

    Arvanitaki, Asimina; Geraci, Andrew A

    2013-02-15

    We propose a tunable resonant sensor to detect gravitational waves in the frequency range of 50-300 kHz using optically trapped and cooled dielectric microspheres or microdisks. The technique we describe can exceed the sensitivity of laser-based gravitational wave observatories in this frequency range, using an instrument of only a few percent of their size. Such a device extends the search volume for gravitational wave sources above 100 kHz by 1 to 3 orders of magnitude, and could detect monochromatic gravitational radiation from the annihilation of QCD axions in the cloud they form around stellar mass black holes within our galaxy due to the superradiance effect.

  19. Harsh Environment Gas Sensor Array for Venus Atmospheric Measurements Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Makel Engineering and the Ohio State University propose to develop a harsh environment tolerant gas sensor array for atmospheric analysis in future Venus missions....

  20. Wave Front Sensor for Solar Concentrator Control

    Science.gov (United States)

    2006-08-31

    absorber used as a model sensor consists of a conical shaped absorber made from one quarter inch (¼”) metal tubing. For actual power conversion, the...tubing would be made from a high temperature metal such as Rhenium or Tungsten. The lens or optic system positions the CCD array to virtual focal...circles to circles with varying amounts of area blackened to represent various stages of misalignment. The experiment proceeded by first using one

  1. PVDF Multielement Lamb Wave Sensor for Structural Health Monitoring.

    Science.gov (United States)

    Ren, Baiyang; Lissenden, Cliff J

    2016-01-01

    The characteristics of Lamb waves, which are multimodal and dispersive, provide both challenges and opportunities for structural health monitoring (SHM). Methods for nondestructive testing with Lamb waves are well established. For example, mode content can be determined by moving a sensor to different positions and then transforming the spatial-temporal data into the wavenumber-frequency domain. This mode content information is very useful because at every frequency each mode has a unique wavestructure, which is largely responsible for its sensitivity to material damage. Furthermore, mode conversion occurs when the waves interact with damage, making mode content an excellent damage detection feature. However, in SHM, the transducers are typically at fixed locations and are immovable. Here, an affixed polyvinylidene fluoride (PVDF) multielement sensor is shown to provide these same capabilities. The PVDF sensor is bonded directly to the waveguide surface, conforms to curved surfaces, has low mass, low profile, low cost, and minimal influence on passing Lamb waves. While the mode receivability is dictated by the sensor being located on the surface of the waveguide, both symmetric and antisymmetric modes can be detected and group velocities measured.

  2. Low cost electrochemical sensor module for measurement of gas concentration

    Science.gov (United States)

    Jasinski, Grzegorz; Strzelczyk, Anna; Koscinski, Piotr

    2016-01-01

    This paper describes a low cost electrochemical sensor module for gas concentration measurement. A module is universal and can be used for many types of electrochemical gas sensors. Device is based on AVR ATmega8 microcontroller. As signal processing circuit a specialized integrated circuit LMP91000 is used. The proposed equipment will be used as a component of electronic nose system employed for classifying and distinguishing different levels of air contamination.

  3. Realisation of porous silicon membranes for gas sensor applications

    Energy Technology Data Exchange (ETDEWEB)

    Gue, A.M. [Centre National de la Recherche Scientifique (CNRS), 31 - Toulouse (France); Taliercio, T.; Massone, E.; Foucaran, A.; Bretagnon, T.; Camassel, J. [Montpellier-2 Univ., 34 (France); Dilhan, M. [C.I.T.A., 31 - Blagnac (France)

    1994-12-31

    In this communication, we report on the elaboration of porous silicon membranes (PSM) for gas sensors application. We have substituted the PTFE membrane of a classical sensor by a porous silicon membrane. The sensor used has been developed by the C.I.T.A. society for the measurement of the oxygen rate dissolved in aqueous solutions. Diffusion curves of oxygen through PSM are discussed further. (author) 10 refs.

  4. Development of gas sensors using ZnO nanostructures

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Different ZnO nanostructures such as nanowires, nanobelts and tetrapods have been grown and used for preparation of thick film (with random grain boundaries) as well as isolated nano- wire/nanobelt gas sensors. Sensitivity of different type of sensors has been studied to H2S and NO gases. The results show ...

  5. Development of gas sensors using ZnO nanostructures

    Indian Academy of Sciences (India)

    Different ZnO nanostructures such as nanowires, nanobelts and tetrapods have been grown and used for preparation of thick film (with random grain boundaries) as well as isolated nanowire/nanobelt gas sensors. Sensitivity of different type of sensors has been studied to H2S and NO gases. The results show that the ...

  6. Quartz crystal microbalance gas sensor with nanocrystalline diamond sensitive layer

    Czech Academy of Sciences Publication Activity Database

    Varga, Marián; Laposa, A.; Kulha, Pavel; Kroutil, J.; Husák, M.; Kromka, Alexander

    2015-01-01

    Roč. 252, č. 11 (2015), s. 2591-2597 ISSN 0370-1972 R&D Projects: GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:68378271 Keywords : gas sensor * nanocrystalline diamond * quartz resonator * thickness shear mode Subject RIV: JB - Sensors, Measurment, Regulation Impact factor: 1.522, year: 2015

  7. Surface Acoustic Wave Vibration Sensors for Measuring Aircraft Flutter

    Science.gov (United States)

    Wilson, William C.; Moore, Jason P.; Juarez, Peter D.

    2016-01-01

    Under NASA's Advanced Air Vehicles Program the Advanced Air Transport Technology (AATT) Project is investigating flutter effects on aeroelastic wings. To support that work a new method for measuring vibrations due to flutter has been developed. The method employs low power Surface Acoustic Wave (SAW) sensors. To demonstrate the ability of the SAW sensor to detect flutter vibrations the sensors were attached to a Carbon fiber-reinforced polymer (CFRP) composite panel which was vibrated at six frequencies from 1Hz to 50Hz. The SAW data was compared to accelerometer data and was found to resemble sine waves and match each other closely. The SAW module design and results from the tests are presented here.

  8. A Review of Carbon Nanotubes-Based Gas Sensors

    Directory of Open Access Journals (Sweden)

    Yun Wang

    2009-01-01

    Full Text Available Gas sensors have attracted intensive research interest due to the demand of sensitive, fast response, and stable sensors for industry, environmental monitoring, biomedicine, and so forth. The development of nanotechnology has created huge potential to build highly sensitive, low cost, portable sensors with low power consumption. The extremely high surface-to-volume ratio and hollow structure of nanomaterials is ideal for the adsorption of gas molecules. Particularly, the advent of carbon nanotubes (CNTs has fuelled the inventions of gas sensors that exploit CNTs' unique geometry, morphology, and material properties. Upon exposure to certain gases, the changes in CNTs' properties can be detected by various methods. Therefore, CNTs-based gas sensors and their mechanisms have been widely studied recently. In this paper, a broad but yet in-depth survey of current CNTs-based gas sensing technology is presented. Both experimental works and theoretical simulations are reviewed. The design, fabrication, and the sensing mechanisms of the CNTs-based gas sensors are discussed. The challenges and perspectives of the research are also addressed in this review.

  9. Temperature-independent polymer optical fiber evanescent wave sensor

    Science.gov (United States)

    Zhong, Nianbing; Liao, Qiang; Zhu, Xun; Zhao, Mingfu; Huang, Yun; Chen, Rong

    2015-06-01

    Although the numerous advantages of polymer optical fibers have been exploited in the fields of sensors and telecommunications, such fibers still experience a critical problem: the temperature dependency. Therefore, we explored the temperature-independent operation of a polymer fiber-optic evanescent wave sensor immersed in distilled water. We investigated variations in the surface morphology, deformation trajectory, refractive index, and weight of the fiber-sensing region with varying water temperature. We also examined the spectral transmission and transmitted light intensity of fibers subjected to a heating-cooling treatment. We observed that the light-transmission modes and sensitivity of the sensor were affected by changes in the surface morphology, diameter, and refractive index of the sensing region caused by changes in temperature. The transmitted light intensity of the sensor was maintained at a constant level after five cycles of the heating-cooling treatment, after which the fibers exhibited a smooth surface, low refractive index, and large fiber diameter. Consequently, we utilized the heating-cooling-treated fiber to realize a temperature-independent, U-shaped polymer fiber-optic evanescent wave sensor. The temperature independence was evaluated using glucose solutions in the range of 10 to 70 °C. The fabricated sensor showed significant temperature independence and high degree of consistency in measuring solutions.

  10. Planar Optical Sensors and Evanescent Wave Effects

    Science.gov (United States)

    Burke, Conor S.; Stránik, Ondrej; McEvoy, Helen M.; MacCraith, Brian D.

    Recent developments in microsystems technology have led to the widespread application of microfabrication techniques for the production of sensor platforms. These techniques have had a major impact on the development of so-called "Lab-on-a-Chip" devices. The major application areas for theses devices are biomedical diagnostics, industrial process monitoring, environmental monitoring, drug discovery, and defence. In the context of biomedical diagnostic applications, for example, such devices are intended to provide quantitative chemical or biochemical information on samples such as blood, sweat and saliva while using minimal sample volume.

  11. Resistive Oxygen Gas Sensors for Harsh Environments

    Directory of Open Access Journals (Sweden)

    Ichiro Matsubara

    2011-03-01

    Full Text Available Resistive oxygen sensors are an inexpensive alternative to the classical potentiometric zirconia oxygen sensor, especially for use in harsh environments and at temperatures of several hundred °C or even higher. This device-oriented paper gives a historical overview on the development of these sensor materials. It focuses especially on approaches to obtain a temperature independent behavior. It is shown that although in the past 40 years there have always been several research groups working concurrently with resistive oxygen sensors, novel ideas continue to emerge today with respect to improvements of the sensor response time, the temperature dependence, the long-term stability or the manufacture of the devices themselves using novel techniques for the sensitive films. Materials that are the focus of this review are metal oxides; especially titania, titanates, and ceria-based formulations.

  12. Passive wireless surface acoustic wave sensors for monitoring sequestration sites CO2 emission

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yizhong [Univ. of Pittsburgh, PA (United States); Chyu, Minking [Univ. of Pittsburgh, PA (United States); Wang, Qing-Ming [Univ. of Pittsburgh, PA (United States)

    2013-02-14

    University of Pittsburgh’s Transducer lab has teamed with the U.S. Department of Energy’s National Energy Technology Laboratory (DOE NETL) to conduct a comprehensive study to develop/evaluate low-cost, efficient CO2 measuring technologies for geological sequestration sites leakage monitoring. A passive wireless CO2 sensing system based on surface acoustic wave technology and carbon nanotube nanocomposite was developed. Surface acoustic wave device was studied to determine the optimum parameters. Delay line structure was adopted as basic sensor structure. CNT polymer nanocomposite was fabricated and tested under different temperature and strain condition for natural environment impact evaluation. Nanocomposite resistance increased for 5 times under pure strain, while the temperature dependence of resistance for CNT solely was -1375ppm/°C. The overall effect of temperature on nanocomposite resistance was -1000ppm/°C. The gas response of the nanocomposite was about 10% resistance increase under pure CO2 . The sensor frequency change was around 300ppm for pure CO2 . With paralyne packaging, the sensor frequency change from relative humidity of 0% to 100% at room temperature decreased from over 1000ppm to less than 100ppm. The lowest detection limit of the sensor is 1% gas concentration, with 36ppm frequency change. Wireless module was tested and showed over one foot transmission distance at preferred parallel orientation.

  13. Fabrication of mechano-optical sensors for hydrogen gas

    NARCIS (Netherlands)

    Pham Van So, P.V.S.; Kauppinen, L.J.; Dijkstra, Mindert; van Wolferen, Hendricus A.G.M.; de Ridder, R.M.; Hoekstra, Hugo

    2009-01-01

    We present results related to the fabrication of a novel and highly sensitive mechano-optical sensor for hydrogen gas, based on microcantilevers, supplied with a selective gas absorbing layer (Pd), suspended above a Si3N4 grated waveguide (GWG). Integrated microcantilever-GWG devices have been

  14. An Atomic Gravitational Wave Interferometric Sensor (AGIS)

    Energy Technology Data Exchange (ETDEWEB)

    Dimopoulos, Savas; /Stanford U., Phys. Dept.; Graham, Peter W.; /SLAC; Hogan, Jason M.; Kasevich, Mark A.; /Stanford U., Phys. Dept.; Rajendran, Surjeet; /SLAC /Stanford U., Phys. Dept.

    2008-08-01

    We propose two distinct atom interferometer gravitational wave detectors, one terrestrial and another satellite-based, utilizing the core technology of the Stanford 10m atom interferometer presently under construction. Each configuration compares two widely separated atom interferometers run using common lasers. The signal scales with the distance between the interferometers, which can be large since only the light travels over this distance, not the atoms. The terrestrial experiment with baseline {approx} 1 km can operate with strain sensitivity {approx} 10{sup -19}/{radical}Hz in the 1 Hz-10 Hz band, inaccessible to LIGO, and can detect gravitational waves from solar mass binaries out to megaparsec distances. The satellite experiment with baseline {approx} 1000 km can probe the same frequency spectrum as LISA with comparable strain sensitivity {approx} 10{sup -20}/{radical}Hz. The use of ballistic atoms (instead of mirrors) as inertial test masses improves systematics coming from vibrations, acceleration noise, and significantly reduces spacecraft control requirements. We analyze the backgrounds in this configuration and discuss methods for controlling them to the required levels.

  15. Corroles-Porphyrins: A Teamwork for Gas Sensor Arrays

    Directory of Open Access Journals (Sweden)

    Rosamaria Capuano

    2015-04-01

    Full Text Available Porphyrins provide an excellent material for chemical sensors, and they have been used for sensing species both in air and solution. In the gas phase, the broad selectivity of porphyrins is largely dependant on molecular features, such as the metal ion complexed at the core of the aromatic ring and the peripheral substituents. Although these features have been largely exploited to design gas sensor arrays, so far, little attention has been devoted to modify the sensing properties of these macrocycles by variation of the molecular aromatic ring. In this paper, the gas sensing properties of a porphyrin analog, the corrole, are studied in comparison with those of the parent porphyrin. Results show that changes in the aromatic ring have important consequences on the sensitivity and selectivity of the sensors and that porphyrins and corroles can positively cooperate to enhance the performance of sensor arrays.

  16. A miniaturized optical gas sensor for natural gas analysis

    NARCIS (Netherlands)

    Ayerden, N.P.

    2016-01-01

    The depletion of domestic reserves and the growing use of sustainable resources forces a transition from the locally produced natural gas with a well-known composition toward the ‘new’ gas with a more flexible composition in the Netherlands. For safe combustion and proper billing, the natural gas

  17. NO2 gas sensor based on hydrogenated graphene

    Science.gov (United States)

    Park, Sungjin; Park, Minji; Kim, Sunghyun; Yi, Sum-Gyun; Kim, Myeongjin; Son, Jangyup; Cha, Jongin; Hong, Jongill; Yoo, Kyung-Hwa

    2017-11-01

    We investigated the relationship between defects in graphene and NO2 gas sensitivity of graphene-based gas sensors. Defects were introduced by hydrogen plasma or ultraviolet (UV)/ozone treatment. As the defect concentration increased, the sensitivity was enhanced, and sub-ppb level detection limit was achieved. UV irradiation was used for recovery at room temperature. However, defects generated by ozone treatment, like graphene oxide, were reduced back to graphene by UV irradiation, so the ozone-treated graphene sensor was not stable over time. In contrast, the response of the hydrogenated graphene sensor was very repeatable because defects generated by hydrogenation was stable enough not to be dehydrogenated by UV irradiation. These results demonstrate that the hydrogenated graphene sensor is a highly sensitive and stable NO2 sensor at room temperature.

  18. Wide Band Low Noise Love Wave Magnetic Field Sensor System.

    Science.gov (United States)

    Kittmann, Anne; Durdaut, Phillip; Zabel, Sebastian; Reermann, Jens; Schmalz, Julius; Spetzler, Benjamin; Meyners, Dirk; Sun, Nian X; McCord, Jeffrey; Gerken, Martina; Schmidt, Gerhard; Höft, Michael; Knöchel, Reinhard; Faupel, Franz; Quandt, Eckhard

    2018-01-10

    We present a comprehensive study of a magnetic sensor system that benefits from a new technique to substantially increase the magnetoelastic coupling of surface acoustic waves (SAW). The device uses shear horizontal acoustic surface waves that are guided by a fused silica layer with an amorphous magnetostrictive FeCoSiB thin film on top. The velocity of these so-called Love waves follows the magnetoelastically-induced changes of the shear modulus according to the magnetic field present. The SAW sensor is operated in a delay line configuration at approximately 150 MHz and translates the magnetic field to a time delay and a related phase shift. The fundamentals of this sensor concept are motivated by magnetic and mechanical simulations. They are experimentally verified using customized low-noise readout electronics. With an extremely low magnetic noise level of ≈100 pT/[Formula: see text], a bandwidth of 50 kHz and a dynamic range of 120 dB, this magnetic field sensor system shows outstanding characteristics. A range of additional measures to further increase the sensitivity are investigated with simulations.

  19. Gas Sensor for Volatile Anesthetic Agents Based on Raman Scattering

    Science.gov (United States)

    Schlüter, Sebastian; Popovska-Leipertz, Nadejda; Seeger, Thomas; Leipertz, Alfred

    Continuous monitoring of respiratory and anesthetic gases during a surgery is of vital importance for the patient safety. Commonly the gas composition is determined by gas chromatography or a combination of IR-spectroscopy and electrochemical sensors. This study presents a concept for an optical sensor based on spontaneous Raman scattering which offers several advantages compared to established systems. All essential components can be detected simultaneously, no sample preparation is necessary and it provides fast response times. To reach the performance of a commonly used gas monitor signal gain has to be increased e.g. by using a multi pass setup.

  20. CHEMICAL SENSORS BASED ON NANOSTRUCTURAL MATERIALS. PART 1. GAS SENSORS. (Review

    Directory of Open Access Journals (Sweden)

    V. V. Khatko

    2014-01-01

    Full Text Available Analysis of modern methods of preparation of gas sensors than utilize nanostructural materials in the basic construction has been made. Nanostructural materials utilization in the sensor increases specific surface area of its sensitive layer. Two groups of the methods that promote to solve this task were selected. The first one is related to the utilization of nanoporous anodic alumina substrate and/or membrane as sensor template. The second one includes the preparation of the sensitive layers based on the 1D–3D nanostructures. Enhancement of the sensor output characteristics is determined by the collection of advanced physicalchemical properties of nanomaterials and nanostructures utilized in the sensor construction.

  1. Study on miss distance based on projectile shock wave sensor

    Science.gov (United States)

    Gu, Guohua; Cheng, Gang; Zhang, Chenjun; Zhou, Lei

    2017-05-01

    The paper establishes miss distance models based on physical characteristic of shock-wave. The aerodynamic theory shows that the shock-wave of flying super-sonic projectile is generated for the projectile compressing and expending its ambient atmosphere. It advances getting miss distance according to interval of the first sensors, which first catches shock-wave, to solve the problem such as noise filtering on severe background, and signals of amplifier vibration dynamic disposal and electromagnetism compatibility, in order to improves the precision and reliability of gathering wave N signals. For the first time, it can identify the kinds of pills and firing units automatically, measure miss distance and azimuth when pills are firing. Application shows that the tactics and technique index is advanced all of the world.

  2. A Surface Acoustic Wave Ethanol Sensor with Zinc Oxide Nanorods

    Directory of Open Access Journals (Sweden)

    Timothy J. Giffney

    2012-01-01

    Full Text Available Surface acoustic wave (SAW sensors are a class of piezoelectric MEMS sensors which can achieve high sensitivity and excellent robustness. A surface acoustic wave ethanol sensor using ZnO nanorods has been developed and tested. Vertically oriented ZnO nanorods were produced on a ZnO/128∘ rotated Y-cut LiNbO3 layered SAW device using a solution growth method with zinc nitrate, hexamethylenetriamine, and polyethyleneimine. The nanorods have average diameter of 45 nm and height of 1 μm. The SAW device has a wavelength of 60 um and a center frequency of 66 MHz at room temperature. In testing at an operating temperature of 270∘C with an ethanol concentration of 2300 ppm, the sensor exhibited a 24 KHz frequency shift. This represents a significant improvement in comparison to an otherwise identical sensor using a ZnO thin film without nanorods, which had a frequency shift of 9 KHz.

  3. Quartz Enhanced Photoacoustic Spectroscopy Based Trace Gas Sensors Using Different Quartz Tuning Forks

    OpenAIRE

    Yufei Ma; Guang Yu; Jingbo Zhang; Xin Yu; Rui Sun; Tittel, Frank K.

    2015-01-01

    A sensitive trace gas sensor platform based on quartz-enhanced photoacoustic spectroscopy (QEPAS) is reported. A 1.395 ?m continuous wave (CW), distributed feedback pigtailed diode laser was used as the excitation source and H2O was selected as the target analyte. Two kinds of quartz tuning forks (QTFs) with a resonant frequency (f0 ) of 30.72 kHz and 38 kHz were employed for the first time as an acoustic wave transducer, respectively for QEPAS instead of a standard QTF with a f0 of 32.768 kH...

  4. Optimization of autonomous magnetic field sensor consisting of giant magnetoimpedance sensor and surface acoustic wave transducer

    KAUST Repository

    Li, Bodong

    2012-11-01

    This paper presents a novel autonomous thin film magnetic field sensor consisting of a tri-layer giant magnetoimpedance sensor and a surface acoustic wave transponder. Double and single electrode interdigital transducer (IDT) designs are employed and compared. The integrated sensor is fabricated using standard microfabrication technology. The results show the double electrode IDT has an advantage in terms of the sensitivity. In order to optimize the matching component, a simulation based on P-matrix is carried out. A maximum change of 2.4 dB of the reflection amplitude and a sensitivity of 0.34 dB/Oe are obtained experimentally. © 2012 IEEE.

  5. CHEMICAL SENSORS BASED ON NANOSTRUCTURAL MATERIALS. PART 1. GAS SENSORS. (Review)

    OpenAIRE

    V. V. Khatko

    2014-01-01

    Analysis of modern methods of preparation of gas sensors than utilize nanostructural materials in the basic construction has been made. Nanostructural materials utilization in the sensor increases specific surface area of its sensitive layer. Two groups of the methods that promote to solve this task were selected. The first one is related to the utilization of nanoporous anodic alumina substrate and/or membrane as sensor template. The second one includes the preparation of the sensitive layer...

  6. Gas Sensors Based on Semiconducting Nanowire Field-Effect Transistors

    Directory of Open Access Journals (Sweden)

    Ping Feng

    2014-09-01

    Full Text Available One-dimensional semiconductor nanostructures are unique sensing materials for the fabrication of gas sensors. In this article, gas sensors based on semiconducting nanowire field-effect transistors (FETs are comprehensively reviewed. Individual nanowires or nanowire network films are usually used as the active detecting channels. In these sensors, a third electrode, which serves as the gate, is used to tune the carrier concentration of the nanowires to realize better sensing performance, including sensitivity, selectivity and response time, etc. The FET parameters can be modulated by the presence of the target gases and their change relate closely to the type and concentration of the gas molecules. In addition, extra controls such as metal decoration, local heating and light irradiation can be combined with the gate electrode to tune the nanowire channel and realize more effective gas sensing. With the help of micro-fabrication techniques, these sensors can be integrated into smart systems. Finally, some challenges for the future investigation and application of nanowire field-effect gas sensors are discussed.

  7. Gas Sensors Based on Semiconducting Nanowire Field-Effect Transistors

    Science.gov (United States)

    Feng, Ping; Shao, Feng; Shi, Yi; Wan, Qing

    2014-01-01

    One-dimensional semiconductor nanostructures are unique sensing materials for the fabrication of gas sensors. In this article, gas sensors based on semiconducting nanowire field-effect transistors (FETs) are comprehensively reviewed. Individual nanowires or nanowire network films are usually used as the active detecting channels. In these sensors, a third electrode, which serves as the gate, is used to tune the carrier concentration of the nanowires to realize better sensing performance, including sensitivity, selectivity and response time, etc. The FET parameters can be modulated by the presence of the target gases and their change relate closely to the type and concentration of the gas molecules. In addition, extra controls such as metal decoration, local heating and light irradiation can be combined with the gate electrode to tune the nanowire channel and realize more effective gas sensing. With the help of micro-fabrication techniques, these sensors can be integrated into smart systems. Finally, some challenges for the future investigation and application of nanowire field-effect gas sensors are discussed. PMID:25232915

  8. Following butter flavour deterioration with an acoustic wave sensor.

    Science.gov (United States)

    Gaspar, Cláudia R B S; Gomes, M Teresa S R

    2012-09-15

    Off-flavours develop naturally in butter and the process is accelerated by heat. An acoustic wave sensor was used to detect the aroma compounds evolved from heated butter and the results have shown that registered marked changes were coincident to odour changes detected by sensory analysis. The flavour compounds have also been analysed by GC/MS for identification. The response of the sensor was fully characterized in terms of the sensitivity to each of the identified compounds, and sensitivities of the system SPME/sensor were compared with the sensitivities of the system SPME/GC/MS. It was found that the sensor analytical system was more sensitive to methylketones than to fatty acids. The SPME/GC/MS system also showed the highest sensitivity to 2-heptanone, followed by 2-nonanone, but third place was occupied by undecanone and butanoic acid, to which the sensor showed moderate sensitivity. 2-heptanone was found to be an appropriate model compound to follow odour changes till the 500 h, and the lower sensitivity of the sensor to butanoic acid showed to be a positive characteristic, as saturation was prevented, and other more subtle changes in the flavour could be perceived. Copyright © 2012 Elsevier B.V. All rights reserved.

  9. A comparative study on simulation performances of rigid and bendable SAW for gas sensor

    Science.gov (United States)

    Sidek, Fatini; Arsat, Rashidah; Ibrahim, Rafidah; Idris, Aizzat Ayuni Mohad; Johari, Zaharah; Ling, Leow Pei

    2017-03-01

    Flexible Surface Acoustic Wave (SAW) devices are very promising technology for various applications that offers excellent flexibility, low in cost and light weight. In this paper, a SAW gas sensor is designed and simulated using COMSOL Multiphysics to investigate the degree of bending effect on the frequency and displacement. The investigations were conducted onto SAW gas sensor as rigid and two different bends direction; bend-in (concave) and bend-out (convex). The operating frequency of the SAW sensor were found to be at the range of 80-200 MHz. The frequency shift of the sensor were obtained after exposing the polyisobutylene (PIB) to the dichloromethane DCM gas which will change the density of sensing layer. From the simulation, it is shown that resonance frequency range of 189MHz for the rigid substrate with displacement of 0.706 nm. Notably, the bending degree of h range from 0.2 µm to 1.25 µm exhibits reduction for displacement and frequency. The higher frequency of bend-out (convex) design achieve is 1.8945 MHz with displacement of 0.68 nm at curve of h= 0.2 µm, Improvement have been observed for the frequency shift of 14 Hz and sensitivity of 1324.24. It shows that the sensor is more sensitive to detect the gas. The evaluation of device bending effect on the eigenfrequency, displacement and frequency shift provide ways to enhance the sensitivity of the gas sensor and expand its possibility of realizing their benefit particularly for sensing device enhancement.

  10. Graphene-Based Long-Period Fiber Grating Surface Plasmon Resonance Sensor for High-Sensitivity Gas Sensing

    Directory of Open Access Journals (Sweden)

    Wei Wei

    2016-12-01

    Full Text Available A graphene-based long-period fiber grating (LPFG surface plasmon resonance (SPR sensor is proposed. A monolayer of graphene is coated onto the Ag film surface of the LPFG SPR sensor, which increases the intensity of the evanescent field on the surface of the fiber and thereby enhances the interaction between the SPR wave and molecules. Such features significantly improve the sensitivity of the sensor. The experimental results demonstrate that the sensitivity of the graphene-based LPFG SPR sensor can reach 0.344 nm%−1 for methane, which is improved 2.96 and 1.31 times with respect to the traditional LPFG sensor and Ag-coated LPFG SPR sensor, respectively. Meanwhile, the graphene-based LPFG SPR sensor exhibits excellent response characteristics and repeatability. Such a SPR sensing scheme offers a promising platform to achieve high sensitivity for gas-sensing applications.

  11. Planar Laser-Based QEPAS Trace Gas Sensor

    OpenAIRE

    Yufei Ma; Ying He; Cheng Chen; Xin Yu; Jingbo Zhang; Jiangbo Peng; Rui Sun; Tittel, Frank K.

    2016-01-01

    A novel quartz enhanced photoacoustic spectroscopy (QEPAS) trace gas detection scheme is reported in this paper. A cylindrical lens was employed for near-infrared laser focusing. The laser beam was shaped as a planar line laser between the gap of the quartz tuning fork (QTF) prongs. Compared with a spherical lens-based QEPAS sensor, the cylindrical lens-based QEPAS sensor has the advantages of easier laser beam alignment and a reduction of stringent stability requirements. Therefore, the repo...

  12. Sensors for online determination of CNG gas quality; Sensorer foer onlinebestaemnning av fordonsgaskvalitet

    Energy Technology Data Exchange (ETDEWEB)

    Stenlaaaas, Ola; Roedjegaard, Henrik

    2012-07-01

    Swedish automotive gas has until now been a very uniform, high quality automotive fuel. Elsewhere in Europe the quality of automotive gas varies significantly. Gas from different sources with different flammability require engine settings adjusted to the chosen gas' unique composition. The prospects for a vehicle-mounted sensor based on infrared technology for gas quality measurement has been studied and solutions are presented with questions that must be answered in a possible future work. The proposed vehicle mounted sensor is based on two channels, one of which measures the partial pressure of methane and the other measures the partial pressure of heavier hydrocarbons in 'equivalents of butane'. Ethane produces a signal of about 0.6 equivalents of butane and propane about 0.8 equivalents. The sensor can be accommodated in a cube with 5 cm side and should be equipped with nipple connections to the existing system. The sensor is expected to work throughout their entire lifetime without manual calibration, through continuous automatic calibration, so-called ABC (Automatic Baseline Compensation). The sensor will have to meet tough quality and environmental standards in which primarily contact ring, vibration and prevention of leakage are identified as extra difficult. Working temperatures and the electrical conditions of power supply and communication interface is considered less challenging. In one million volumes, the cost per sensor could be 200 to 300 SEK.

  13. Towards Enhanced Gas Sensor Performance with Fluoropolymer Membranes

    Directory of Open Access Journals (Sweden)

    Thorsten Graunke

    2016-09-01

    Full Text Available In this paper we report on how to increase the selectivity of gas sensors by using fluoropolymer membranes. The mass transport of polar and non-polar gases through a polymer membrane matrix was studied by systematic selection of polymers with different degrees of fluorination, as well as polymers whose monomers have ether groups (-O- in addition to fluorine groups (-F. For the study, a set of application-relevant gases including H2, CO, CO2, NO2, methane, ethanol, acetone, and acetaldehyde as well as various concentrations of relative humidity were used. These gases have different functional groups and polarities, yet have a similar kinetic diameter and are therefore typically difficult to separate. The concentrations of the gases were chosen according to international indicative limit values (TWA, STEL. To measure the concentration in the feed and permeate, we used tin-dioxide-based metal oxide gas sensors with palladium catalyst (SnO2:Pd, catalytic sensors (also SnO2:Pd-based and thermal conductivity sensors. This allows a close examination of the interdependence of diffusion and physicochemical operating principle of the sensor. Our goal is to increase the selectivity of gas sensors by using inexpensive fluoropolymer membranes. The measurements showed that through membranes with low polarity, preferably non-polar gases are transported. Furthermore, the degree of crystallization influences the permeability and selectivity of a polymer membrane. Basically the polar polymers showed a higher permeability to water vapor and polar substances than non-polar polymer membranes.

  14. Illicit material detector based on gas sensors and neural networks

    Science.gov (United States)

    Grimaldi, Vincent; Politano, Jean-Luc

    1997-02-01

    In accordance with its missions, le Centre de Recherches et d'Etudes de la Logistique de la Police Nationale francaise (CREL) has been conducting research for the past few years targeted at detecting drugs and explosives. We have focused our approach of the underlying physical and chemical detection principles on solid state gas sensors, in the hope of developing a hand-held drugs and explosives detector. The CREL and Laboratory and Scientific Services Directorate are research partners for this project. Using generic hydrocarbon, industrially available, metal oxide sensors as illicit material detectors, requires usage precautions. Indeed, neither the product's concentrations, nor even the products themselves, belong to the intended usage specifications. Therefore, the CREL is currently investigating two major research topics: controlling the sensor's environment: with environmental control we improve the detection of small product concentration; determining detection thresholds: both drugs and explosives disseminate low gas concentration. We are attempting to quantify the minimal concentration which triggers detection. In the long run, we foresee a computer-based tool likely to detect a target gas in a noisy atmosphere. A neural network is the suitable tool for interpreting the response of heterogeneous sensor matrix. This information processing structure, alongside with proper sensor environment control, will lessen the repercussions of common MOS sensor sensitivity characteristic dispersion.

  15. MEMS device for mass market gas and chemical sensors

    Science.gov (United States)

    Kinkade, Brian R.; Daly, James T.; Johnson, Edward A.

    2000-08-01

    Gas and chemical sensors are used in many applications. Industrial health and safety monitors allow companies to meet OSHA requirements by detecting harmful levels of toxic or combustible gases. Vehicle emissions are tested during annual inspections. Blood alcohol breathalizers are used by law enforcement. Refrigerant leak detection ensures that the Earth's ozone layer is not being compromised. Industrial combustion emissions are also monitored to minimize pollution. Heating and ventilation systems watch for high levels of carbon dioxide (CO2) to trigger an increase in fresh air exchange. Carbon monoxide detectors are used in homes to prevent poisoning from poor combustion ventilation. Anesthesia gases are monitored during a patients operation. The current economic reality is that two groups of gas sensor technologies are competing in two distinct existing market segments - affordable (less reliable) chemical reaction sensors for consumer markets and reliable (expensive) infrared (IR) spectroscopic sensors for industrial, laboratory, and medical instrumentation markets. Presently high volume mass-market applications are limited to CO detectros and on-board automotive emissions sensors. Due to reliability problems with electrochemical sensor-based CO detectors there is a hesitancy to apply these sensors in other high volume applications. Applications such as: natural gas leak detection, non-invasive blood glucose monitoring, home indoor air quality, personal/portable air quality monitors, home fire/burnt cooking detector, and home food spoilage detectors need a sensor that is a small, efficient, accurate, sensitive, reliable, and inexpensive. Connecting an array of these next generation gas sensors to wireless networks that are starting to proliferate today creates many other applications. Asthmatics could preview the air quality of their destinations as they venture out into the day. HVAC systems could determine if fresh air intake was actually better than the air

  16. Fiber optic gas sensor with nanocrystalline ZnO

    Science.gov (United States)

    Renganathan, B.; Ganesan, A. R.

    2014-01-01

    A fiber optic gas sensor with a PMMA fiber whose clad is modified with chemically sensitive nano-crystalline zinc oxide has been developed and investigated to detect acetone, isopropyl alcohol and benzene gases. The spectral characteristics of the sensor were recorded for different concentrations ranging from (0-500 ppm) for these gases both with as-prepared and annealed nanocrystalline ZnO, and the influence of annealing on the gas sensing has been studied.The response time and recovery time were found to be 48 min. and 42 min. respectively for 500 ppm concentration.

  17. Design of micro-sensor-array detector for toxic gas

    Science.gov (United States)

    Liao, Hai-yang; Tian, Peng

    2010-08-01

    To quickly measure the trace concentration of the single component toxic gas (e.g. sarin), a micro-array toxic gas detector is designed. A 3 x 3 gas sensor array with metalloporphyrins as sensitive materials is introduced. A micro-capsule that can be easy to be loaded and unloaded is designed for the gas reaction. A fiber-array optical path is designed, which is based on the principle that gas sensors will show different colors after reaction with the toxic gas. The tricolor information about the concentration of gas is collected by the color liner CCD. A control handling system with C8051F021 MCU as the core is implemented and embedded into the detector to perform the functions of gas sampling, data collection and analysis calculation. Data acquisition experimental results show that the proposed scheme can effectively collect the color information after gas reaction. Moreover, the system has many important advantages, such as small size, compact structure, high degree of automation, fast detection speed and high performance-cost ratio, etc.

  18. Planar Laser-Based QEPAS Trace Gas Sensor

    Directory of Open Access Journals (Sweden)

    Yufei Ma

    2016-06-01

    Full Text Available A novel quartz enhanced photoacoustic spectroscopy (QEPAS trace gas detection scheme is reported in this paper. A cylindrical lens was employed for near-infrared laser focusing. The laser beam was shaped as a planar line laser between the gap of the quartz tuning fork (QTF prongs. Compared with a spherical lens-based QEPAS sensor, the cylindrical lens-based QEPAS sensor has the advantages of easier laser beam alignment and a reduction of stringent stability requirements. Therefore, the reported approach is useful in long-term and continuous sensor operation.

  19. Planar Laser-Based QEPAS Trace Gas Sensor.

    Science.gov (United States)

    Ma, Yufei; He, Ying; Chen, Cheng; Yu, Xin; Zhang, Jingbo; Peng, Jiangbo; Sun, Rui; Tittel, Frank K

    2016-06-28

    A novel quartz enhanced photoacoustic spectroscopy (QEPAS) trace gas detection scheme is reported in this paper. A cylindrical lens was employed for near-infrared laser focusing. The laser beam was shaped as a planar line laser between the gap of the quartz tuning fork (QTF) prongs. Compared with a spherical lens-based QEPAS sensor, the cylindrical lens-based QEPAS sensor has the advantages of easier laser beam alignment and a reduction of stringent stability requirements. Therefore, the reported approach is useful in long-term and continuous sensor operation.

  20. Study of thermal shock wave in shock-compressed He II induced by gas dynamic shock wave impingement

    Science.gov (United States)

    Yang, H. S.; Ueta, Y.; Nagai, H.; Murakami, M.; Yanaka, K.

    2002-05-01

    Strong thermal shock waves induced by the impingement of a gas dynamic shock wave onto a He II free surface in the superfluid shock tube facility were investigated by measuring temperature variation with superconductive temperature sensors and by Schlieren visualization method with an ultra high-speed video camera (40,500 pictures/sec). The heat transfer from shock-compressed high temperature vapor to He II forming a thermal shock wave is considered. The temperature rise ratio of an induced thermal shock to that of an incident gas dynamic shock wave was found to be very small, as small as 0.003 at 1.80 K. It is seen that the most part of the heat do not be transmitted into bulk He II because a high density quantized vortex layer is rapidly developed in a thermal boundary layer in the immediate vicinity of the vapor-He II interface. The existence of a thermal boundary layer with a large temperature gradient in which the physical state varies from supercritical helium to He II temperature and the rapid growth up to about 1 mm in thickness of the layer with such as thermal conduction process are measured with the temperature measurements. Besides, it is also found that high compressibility of He II results in formation of a dark zone near the interface region that is extended toward bulk He II.

  1. Chemical Gas Sensors for Aerospace Applications

    Science.gov (United States)

    Hunter, Gary W.; Liu, C. C.

    1998-01-01

    Chemical sensors often need to be specifically designed (or tailored) to operate in a given environment. It is often the case that a chemical sensor that meets the needs of one application will not function adequately in another application. The more demanding the environment and specialized the requirement, the greater the need to adapt exiting sensor technologies to meet these requirements or, as necessary, develop new sensor technologies. Aerospace (aeronautic and space) applications are particularly challenging since often these applications have specifications which have not previously been the emphasis of commercial suppliers. Further, the chemical sensing needs of aerospace applications have changed over the years to reflect the changing emphasis of society. Three chemical sensing applications of particular interest to the National Aeronautics and Space Administration (NASA) which illustrate these trends are launch vehicle leak detection, emission monitoring, and fire detection. Each of these applications reflects efforts ongoing throughout NASA. As described in NASA's "Three Pillars for Success", a document which outlines NASA's long term response to achieve the nation's priorities in aerospace transportation, agency wide objectives include: improving safety and decreasing the cost of space travel, significantly decreasing the amount of emissions produced by aeronautic engines, and improving the safety of commercial airline travel. As will be discussed below, chemical sensing in leak detection, emission monitoring, and fire detection will help enable the agency to meet these objectives. Each application has vastly different problems associated with the measurement of chemical species. Nonetheless, the development of a common base technology can address the measurement needs of a number of applications.

  2. Nanoparticle-based gas sensors and methods of using the same

    Science.gov (United States)

    Mickelson, William; Zettl, Alex

    2017-10-17

    Gas sensors are provided. The gas sensors include a gas sensing element having metal oxide nanoparticles and a thin-film heating element. Systems that include the gas sensors, as well as methods of using the gas sensors, are also provided. Embodiments of the present disclosure find use in a variety of different applications, including detecting whether an analyte is present in a gaseous sample.

  3. Quartz Enhanced Photoacoustic Spectroscopy Based Trace Gas Sensors Using Different Quartz Tuning Forks

    Directory of Open Access Journals (Sweden)

    Yufei Ma

    2015-03-01

    Full Text Available A sensitive trace gas sensor platform based on quartz-enhanced photoacoustic spectroscopy (QEPAS is reported. A 1.395 μm continuous wave (CW, distributed feedback pigtailed diode laser was used as the excitation source and H2O was selected as the target analyte. Two kinds of quartz tuning forks (QTFs with a resonant frequency (f0 of 30.72 kHz and 38 kHz were employed for the first time as an acoustic wave transducer, respectively for QEPAS instead of a standard QTF with a f0 of 32.768 kHz. The QEPAS sensor performance using the three different QTFs was experimentally investigated and theoretically analyzed. A minimum detection limit of 5.9 ppmv and 4.3 ppmv was achieved for f0 of 32.768 kHz and 30.72 kHz, respectively.

  4. Quartz enhanced photoacoustic spectroscopy based trace gas sensors using different quartz tuning forks.

    Science.gov (United States)

    Ma, Yufei; Yu, Guang; Zhang, Jingbo; Yu, Xin; Sun, Rui; Tittel, Frank K

    2015-03-27

    A sensitive trace gas sensor platform based on quartz-enhanced photoacoustic spectroscopy (QEPAS) is reported. A 1.395 μm continuous wave (CW), distributed feedback pigtailed diode laser was used as the excitation source and H2O was selected as the target analyte. Two kinds of quartz tuning forks (QTFs) with a resonant frequency (f0) of 30.72 kHz and 38 kHz were employed for the first time as an acoustic wave transducer, respectively for QEPAS instead of a standard QTF with a f0 of 32.768 kHz. The QEPAS sensor performance using the three different QTFs was experimentally investigated and theoretically analyzed. A minimum detection limit of 5.9 ppmv and 4.3 ppmv was achieved for f0 of 32.768 kHz and 30.72 kHz, respectively.

  5. A Guided Wave Sensor Enabling Simultaneous Wavenumber-Frequency Analysis for Both Lamb and Shear-Horizontal Waves.

    Science.gov (United States)

    Ren, Baiyang; Cho, Hwanjeong; Lissenden, Cliff J

    2017-03-01

    Guided waves in plate-like structures have been widely investigated for structural health monitoring. Lamb waves and shear horizontal (SH) waves, two commonly used types of waves in plates, provide different benefits for the detection of various types of defects and material degradation. However, there are few sensors that can detect both Lamb and SH waves and also resolve their modal content, namely the wavenumber-frequency spectrum. A sensor that can detect both waves is desirable to take full advantage of both types of waves in order to improve sensitivity to different discontinuity geometries. We demonstrate that polyvinylidene difluoride (PVDF) film provides the basis for a multi-element array sensor that detects both Lamb and SH waves and also measures their modal content, i.e., the wavenumber-frequency spectrum.

  6. ZnO Coated Nanospring-Based Gas Sensors

    Science.gov (United States)

    Bakharev, Pavel Viktorovich

    The current research demonstrates new techniques for characterization of electrical transport properties of the metal oxide polycrystalline structures, gas and vapor phase kinetics, surface processes such as gas-surface, vapor-surface interactions and redox processes by applying novel gas sensing devices. Real-time sensor electrical response characteristics obtained under highly controlled laboratory conditions have been used to characterize corresponding surface interactions and electrical properties of the gas sensitive structures. Novel redox chemical sensors (chemiresistors) have been fabricated with 3-D and 1-D ZnO coated nanospring (NS) structures. Silica NSs served as insulating scaffolding for a ZnO gas sensitive layer and has been grown via a vapor-liquid-solid (VLS) mechanism by using a chemical vapor deposition (CVD) technique. The NSs have been coated with polycrystalline ZnO by atomic layer deposition (ALD). The chemiresistor devices have been thoroughly characterized in terms of their crystal structures (by XRD, FESEM, TEM, and ellipsometry) and their electrical response properties. A 3-D gas sensor has been constructed from a xenon light bulb by coating it with a 3-D zinc oxide coated silica nanospring mat, where the xenon light bulb served as a sensor heater. This inexpensive sensor platform has been used to characterize gas-solid, vapor-solid, and redox processes. The optimal temperature of the gas sensitive ZnO layer, the temperature of the vapor-gas mixture and the crystal structure of the gas sensitive layer have been determined to reach the highest sensitivity of the gas sensors. The activation energy of toluene oxidation (Ed) on the ZnO surface and the activation energy of oxidation (Ea) of the depleted ZnO surface have been determined and analyzed. A 1-D chemiresistor has been fabricated with a single ZnO coated silica nanospring by photolithography. The question of sensor sensitivity of MOS nanomaterials and MOS thin films has been addressed

  7. Ionizing gas breakdown waves in strong electric fields.

    Science.gov (United States)

    Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

    1972-01-01

    A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

  8. Optimized Feature Extraction for Temperature-Modulated Gas Sensors

    Directory of Open Access Journals (Sweden)

    Alexander Vergara

    2009-01-01

    Full Text Available One of the most serious limitations to the practical utilization of solid-state gas sensors is the drift of their signal. Even if drift is rooted in the chemical and physical processes occurring in the sensor, improved signal processing is generally considered as a methodology to increase sensors stability. Several studies evidenced the augmented stability of time variable signals elicited by the modulation of either the gas concentration or the operating temperature. Furthermore, when time-variable signals are used, the extraction of features can be accomplished in shorter time with respect to the time necessary to calculate the usual features defined in steady-state conditions. In this paper, we discuss the stability properties of distinct dynamic features using an array of metal oxide semiconductors gas sensors whose working temperature is modulated with optimized multisinusoidal signals. Experiments were aimed at measuring the dispersion of sensors features in repeated sequences of a limited number of experimental conditions. Results evidenced that the features extracted during the temperature modulation reduce the multidimensional data dispersion among repeated measurements. In particular, the Energy Signal Vector provided an almost constant classification rate along the time with respect to the temperature modulation.

  9. A Miniaturized QEPAS Trace Gas Sensor with a 3D-Printed Acoustic Detection Module

    Directory of Open Access Journals (Sweden)

    Xiaotao Yang

    2017-07-01

    Full Text Available A 3D printing technique was introduced to a quartz-enhanced photoacoustic spectroscopy (QEPAS sensor and is reported for the first time. The acoustic detection module (ADM was designed and fabricated using the 3D printing technique and the ADM volume was compressed significantly. Furthermore, a small grin lens was used for laser focusing and facilitated the beam adjustment in the 3D-printed ADM. A quartz tuning fork (QTF with a low resonance frequency of 30.72 kHz was used as the acoustic wave transducer and acetylene (C2H2 was chosen as the analyte. The reported miniaturized QEPAS trace gas sensor is useful in actual sensor applications.

  10. A Miniaturized QEPAS Trace Gas Sensor with a 3D-Printed Acoustic Detection Module.

    Science.gov (United States)

    Yang, Xiaotao; Xiao, Youhong; Ma, Yufei; He, Ying; Tittel, Frank K

    2017-07-31

    A 3D printing technique was introduced to a quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor and is reported for the first time. The acoustic detection module (ADM) was designed and fabricated using the 3D printing technique and the ADM volume was compressed significantly. Furthermore, a small grin lens was used for laser focusing and facilitated the beam adjustment in the 3D-printed ADM. A quartz tuning fork (QTF) with a low resonance frequency of 30.72 kHz was used as the acoustic wave transducer and acetylene (C₂H₂) was chosen as the analyte. The reported miniaturized QEPAS trace gas sensor is useful in actual sensor applications.

  11. Development of an Exhaled Breath Monitoring System with Semiconductive Gas Sensors, a Gas Condenser Unit, and Gas Chromatograph Columns.

    Science.gov (United States)

    Itoh, Toshio; Miwa, Toshio; Tsuruta, Akihiro; Akamatsu, Takafumi; Izu, Noriya; Shin, Woosuck; Park, Jangchul; Hida, Toyoaki; Eda, Takeshi; Setoguchi, Yasuhiro

    2016-11-10

    Various volatile organic compounds (VOCs) in breath exhaled by patients with lung cancer, healthy controls, and patients with lung cancer who underwent surgery for resection of cancer were analyzed by gas condenser-equipped gas chromatography-mass spectrometry (GC/MS) for development of an exhaled breath monitoring prototype system involving metal oxide gas sensors, a gas condenser, and gas chromatography columns. The gas condenser-GC/MS analysis identified concentrations of 56 VOCs in the breath exhaled by the test population of 136 volunteers (107 patients with lung cancer and 29 controls), and selected four target VOCs, nonanal, acetoin, acetic acid, and propanoic acid, for use with the condenser, GC, and sensor-type prototype system. The prototype system analyzed exhaled breath samples from 101 volunteers (74 patients with lung cancer and 27 controls). The prototype system exhibited a level of performance similar to that of the gas condenser-GC/MS system for breath analysis.

  12. Fast response time alcohol gas sensor using nanocrystalline F ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 36; Issue 4. Fast response time alcohol gas sensor using nanocrystalline F-doped SnO2 films derived via sol–gel method. Sarbani Basu Yeong-Her Wang C Ghanshyam Pawan Kapur. Volume 36 Issue 4 August 2013 pp 521-533 ...

  13. Development of nanostructured protective "sight glasses" for IR gas sensors

    DEFF Research Database (Denmark)

    Bergmann, René; Davis, Zachary James; Schmidt, Michael Stenbæk

    2011-01-01

    In this work protective "sight glasses" for infrared gas sensors showing a sub-wavelength nanostructure with random patterns have been fabricated by reactive ion etching (RIE) in an easy and comparable cheap single step mask-less process. By an organic coating, the intrinsic water repellent prope...

  14. Thin-film antifuses for pellistor type gas sensors

    NARCIS (Netherlands)

    Kovalgin, Alexeij Y.; Holleman, J.; van den Berg, Albert; Wallinga, Hans

    2001-01-01

    This work extends our previously reported idea of using the nano-scale conductive link (antifuse) as a combined heating /detecting element in a Pellistor-type gas sensor. Our new thin-film antifuse is designed in such a way that the oxide, for minimising the bulk influence on surface temperature,

  15. Improved zinc oxide film for gas sensor applications

    Indian Academy of Sciences (India)

    Zinc oxide (ZnO) is a versatile material for different commercial applications such as transparent electrodes, piezoelectric devices, varistors, SAW devices etc because of its high piezoelectric coupling, greater stability of its hexagonal phase and its pyroelectric property. In fact, ZnO is a potential material for gas sensor ...

  16. Conductivity modeling of gas sensors based on copper ...

    African Journals Online (AJOL)

    The main objective of this work is to study the electronic conductivity of copper phthalocyanine (CuPc) thin films in presence of certain strong oxidizing gases involved in air pollution, particularly NO2, for use as gas sensor devices. To achieve this objective, the first part presents a study of the conductivity evolution of these ...

  17. Harmful Gas Recognition Exploiting a CTL Sensor Array

    Directory of Open Access Journals (Sweden)

    Yao Zheng

    2013-10-01

    Full Text Available In this paper, a novel cataluminescence (CTL-based sensor array consisting of nine types of catalytic materials is developed for the recognition of several harmful gases, namely carbon monoxide, acetone, chloroform and toluene. First, the experimental setup is constructed by using sensing nanomaterials, a heating plate, a pneumatic pump, a gas flow meter, a digital temperature device, a camera and a BPCL Ultra Weak Chemiluminescence Analyzer. Then, unique CTL patterns for the four types of harmful gas are obtained from the sensor array. The harmful gases are successful recognized by the PCA method. The optimal conditions are also investigated. Finally, experimental results show high sensitivity, long-term stability and good linearity of the sensor array, which combined with simplicity, make our system a promising application in this field.

  18. Hydrogen Gas Sensors Based on Semiconductor Oxide Nanostructures

    Science.gov (United States)

    Gu, Haoshuang; Wang, Zhao; Hu, Yongming

    2012-01-01

    Recently, the hydrogen gas sensing properties of semiconductor oxide (SMO) nanostructures have been widely investigated. In this article, we provide a comprehensive review of the research progress in the last five years concerning hydrogen gas sensors based on SMO thin film and one-dimensional (1D) nanostructures. The hydrogen sensing mechanism of SMO nanostructures and some critical issues are discussed. Doping, noble metal-decoration, heterojunctions and size reduction have been investigated and proved to be effective methods for improving the sensing performance of SMO thin films and 1D nanostructures. The effect on the hydrogen response of SMO thin films and 1D nanostructures of grain boundary and crystal orientation, as well as the sensor architecture, including electrode size and nanojunctions have also been studied. Finally, we also discuss some challenges for the future applications of SMO nanostructured hydrogen sensors. PMID:22778599

  19. Hydrogen Gas Sensors Based on Semiconductor Oxide Nanostructures

    Directory of Open Access Journals (Sweden)

    Yongming Hu

    2012-04-01

    Full Text Available Recently, the hydrogen gas sensing properties of semiconductor oxide (SMO nanostructures have been widely investigated. In this article, we provide a comprehensive review of the research progress in the last five years concerning hydrogen gas sensors based on SMO thin film and one-dimensional (1D nanostructures. The hydrogen sensing mechanism of SMO nanostructures and some critical issues are discussed. Doping, noble metal-decoration, heterojunctions and size reduction have been investigated and proved to be effective methods for improving the sensing performance of SMO thin films and 1D nanostructures. The effect on the hydrogen response of SMO thin films and 1D nanostructures of grain boundary and crystal orientation, as well as the sensor architecture, including electrode size and nanojunctions have also been studied. Finally, we also discuss some challenges for the future applications of SMO nanostructured hydrogen sensors.

  20. Guided wave and damage detection in composite laminates using different fiber optic sensors.

    Science.gov (United States)

    Li, Fucai; Murayama, Hideaki; Kageyama, Kazuro; Shirai, Takehiro

    2009-01-01

    Guided wave detection using different fiber optic sensors and their applications in damage detection for composite laminates were systematically investigated and compared in this paper. Two types of fiber optic sensors, namely fiber Bragg gratings (FBG) and Doppler effect-based fiber optic (FOD) sensors, were addressed and guided wave detection systems were constructed for both types. Guided waves generated by a piezoelectric transducer were propagated through a quasi-isotropic carbon fiber reinforced plastic (CFRP) laminate and acquired by these fiber optic sensors. Characteristics of these fiber optic sensors in ultrasonic guided wave detection were systematically compared. Results demonstrated that both the FBG and FOD sensors can be applied in guided wave and damage detection for the CFRP laminates. The signal-to-noise ratio (SNR) of guided wave signal captured by an FOD sensor is relatively high in comparison with that of the FBG sensor because of their different physical principles in ultrasonic detection. Further, the FOD sensor is sensitive to the damage-induced fundamental shear horizontal (SH(0)) guided wave that, however, cannot be detected by using the FBG sensor, because the FOD sensor is omnidirectional in ultrasound detection and, in contrast, the FBG sensor is severely direction dependent.

  1. Guided Wave and Damage Detection in Composite Laminates Using Different Fiber Optic Sensors

    Directory of Open Access Journals (Sweden)

    Fucai Li

    2009-05-01

    Full Text Available Guided wave detection using different fiber optic sensors and their applications in damage detection for composite laminates were systematically investigated and compared in this paper. Two types of fiber optic sensors, namely fiber Bragg gratings (FBG and Doppler effect-based fiber optic (FOD sensors, were addressed and guided wave detection systems were constructed for both types. Guided waves generated by a piezoelectric transducer were propagated through a quasi-isotropic carbon fiber reinforced plastic (CFRP laminate and acquired by these fiber optic sensors. Characteristics of these fiber optic sensors in ultrasonic guided wave detection were systematically compared. Results demonstrated that both the FBG and FOD sensors can be applied in guided wave and damage detection for the CFRP laminates. The signal-to-noise ratio (SNR of guided wave signal captured by an FOD sensor is relatively high in comparison with that of the FBG sensor because of their different physical principles in ultrasonic detection. Further, the FOD sensor is sensitive to the damage-induced fundamental shear horizontal (SH0 guided wave that, however, cannot be detected by using the FBG sensor, because the FOD sensor is omnidirectional in ultrasound detection and, in contrast, the FBG sensor is severely direction dependent.

  2. A Microring Temperature Sensor Based on the Surface Plasmon Wave

    Directory of Open Access Journals (Sweden)

    Wenchao Li

    2015-01-01

    Full Text Available A structure of microring sensor suitable for temperature measurement based on the surface plasmon wave is put forward in this paper. The sensor uses surface plasmon multilayer waveguiding structure in the vertical direction and U-shaped microring structure in the horizontal direction and utilizes SOI as the thermal material. The transfer function derivation of the structure of surface plasmon microring sensor is according to the transfer matrix method. While the change of refractive index of Si is caused by the change of ambient temperature, the effective refractive index of the multilayer waveguiding structure is changed, resulting in the drifting of the sensor output spectrum. This paper focuses on the transmission characteristics of multilayer waveguide structure and the impact on the output spectrum caused by refractive index changes in temperature parts. According to the calculation and simulation, the transmission performance of the structure is stable and the sensitivity is good. The resonance wavelength shift can reach 0.007 μm when the temperature is increased by 100 k and FSR can reach about 60 nm. This structure achieves a high sensitivity in the temperature sense taking into account a wide range of filter frequency selections, providing a theoretical basis for the preparation of microoptics.

  3. Data set from gas sensor array under flow modulation.

    Science.gov (United States)

    Ziyatdinov, Andrey; Fonollosa, Jordi; Fernández, Luis; Gutiérrez-Gálvez, Agustín; Marco, Santiago; Perera, Alexandre

    2015-06-01

    Recent studies in neuroscience suggest that sniffing, namely sampling odors actively, plays an important role in olfactory system, especially in certain scenarios such as novel odorant detection. While the computational advantages of high frequency sampling have not been yet elucidated, here, in order to motivate further investigation in active sampling strategies, we share the data from an artificial olfactory system made of 16 MOX gas sensors under gas flow modulation. The data were acquired on a custom set up featured by an external mechanical ventilator that emulates the biological respiration cycle. 58 samples were recorded in response to a relatively broad set of 12 gas classes, defined from different binary mixtures of acetone and ethanol in air. The acquired time series show two dominant frequency bands: the low-frequency signal corresponds to a conventional response curve of a sensor in response to a gas pulse, and the high-frequency signal has a clear principal harmonic at the respiration frequency. The data are related to the study in [1], and the data analysis results reported there should be considered as a reference point. The data presented here have been deposited to the web site of The University of California at Irvine (UCI) Machine Learning Repository (https://archive.ics.uci.edu/ml/datasets/Gas+sensor+array+under+flow+modulation). The code repository for reproducible analysis applied to the data is hosted at the GutHub web site (https://github.com/variani/pulmon). The data and code can be used upon citation of [1].

  4. A smart microelectromechanical sensor and switch triggered by gas

    KAUST Repository

    Bouchaala, Adam M.

    2016-07-05

    There is an increasing interest to realize smarter sensors and actuators that can deliver a multitude of sophisticated functionalities while being compact in size and of low cost. We report here combining both sensing and actuation on the same device based on a single microstructure. Specifically, we demonstrate a smart resonant gas (mass) sensor, which in addition to being capable of quantifying the amount of absorbed gas, can be autonomously triggered as an electrical switch upon exceeding a preset threshold of absorbed gas. Toward this, an electrostatically actuated polymer microbeam is fabricated and is then functionalized with a metal-organic framework, namely, HKUST-1. The microbeam is demonstrated to absorb vapors up to a certain threshold, after which is shown to collapse through the dynamic pull-in instability. Upon pull-in, the microstructure can be made to act as an electrical switch to achieve desirable actions, such as alarming.

  5. Nanostructured Gas Sensors for Health Care: An Overview.

    Science.gov (United States)

    Kaushik, Ajeet; Kumar, Rajesh; Jayant, Rahul Dev; Nair, Madhavan

    2015-07-01

    Nanostructured platforms have been utilized for fabrication of small, sensitive and reliable gas sensing devices owing to high functionality, enhanced charge transport and electro-catalytic property. As a result of globalization, rapid, sensitive and selective detection of gases in environment is essential for health care and security. Nonmaterial such as metal, metal oxides, organic polymers, and organic-inorganic hybrid nanocomposites exhibit interesting optical, electrical, magnetic and molecular properties, and hence are found potential gas sensing materials. Morphological, electrical, and optical properties of such nanostructures can be tailored via controlling the precursor concentration and synthesis conditions resulting to achieve desired sensing. This review presents applications of nano-enabling gas sensors to detect gases for environment monitoring. The recent update, challenges, and future vision for commercial applications of such sensor are also described here.

  6. A smart microelectromechanical sensor and switch triggered by gas

    Science.gov (United States)

    Bouchaala, Adam; Jaber, Nizar; Shekhah, Osama; Chernikova, Valeriya; Eddaoudi, Mohamed; Younis, Mohammad I.

    2016-07-01

    There is an increasing interest to realize smarter sensors and actuators that can deliver a multitude of sophisticated functionalities while being compact in size and of low cost. We report here combining both sensing and actuation on the same device based on a single microstructure. Specifically, we demonstrate a smart resonant gas (mass) sensor, which in addition to being capable of quantifying the amount of absorbed gas, can be autonomously triggered as an electrical switch upon exceeding a preset threshold of absorbed gas. Toward this, an electrostatically actuated polymer microbeam is fabricated and is then functionalized with a metal-organic framework, namely, HKUST-1. The microbeam is demonstrated to absorb vapors up to a certain threshold, after which is shown to collapse through the dynamic pull-in instability. Upon pull-in, the microstructure can be made to act as an electrical switch to achieve desirable actions, such as alarming.

  7. Nanostructured Gas Sensors for Health Care: An Overview

    Science.gov (United States)

    Kaushik, Ajeet; Kumar, Rajesh; Jayant, Rahul Dev; Nair, Madhavan

    2015-01-01

    Nanostructured platforms have been utilized for fabrication of small, sensitive and reliable gas sensing devices owing to high functionality, enhanced charge transport and electro-catalytic property. As a result of globalization, rapid, sensitive and selective detection of gases in environment is essential for health care and security. Nonmaterial such as metal, metal oxides, organic polymers, and organic-inorganic hybrid nanocomposites exhibit interesting optical, electrical, magnetic and molecular properties, and hence are found potential gas sensing materials. Morphological, electrical, and optical properties of such nanostructures can be tailored via controlling the precursor concentration and synthesis conditions resulting to achieve desired sensing. This review presents applications of nano-enabling gas sensors to detect gases for environment monitoring. The recent update, challenges, and future vision for commercial applications of such sensor are also described here. PMID:26491544

  8. Fiber optic evanescent wave (FOEW) microbial sensor for dental application

    Science.gov (United States)

    Kishen, Anil; John, M. S.; Chen, Jun-Wei; Lim, Chu S.; Hu, Xiao; Asundi, Anand K.

    2001-10-01

    In this work a new approach based on the fiber Optic Evanescent Wave (FOEW) Spectroscopy is developed for the effective determination of dental caries activity in human saliva. The biosensor design utilized the exponentially decaying wave that extends to the lower index region of the optical fiber's core-cladding interface. In order to achieve this, a short length of the cladding is removed and the fiber core surface is coated with a porous glass medium using sol-gel technique. The acidogenic profile resulting from the Streptococcus mutans activity in the human saliva is monitored using an indicator, which was encapsulated within the porous coating. These investigations display the potential benefits of FOEW based microbial sensor to monitor caries activity in human saliva.

  9. PASSIVE WIRELESS MULTI-SENSOR TEMPERATURE AND PRESSURE SENSING SYSTEM USING ACOUSTIC WAVE DEVICES Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes the development of passive surface acoustic wave (SAW) sensors and multi-sensor systems for NASA application to remote wireless sensing of...

  10. Passive Wireless Multi-Sensor Temperature and Pressure Sensing System Using Acoustic Wave Devices Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes the continued development of passive, orthogonal frequency coded (OFC) surface acoustic wave (SAW) sensors and multi-sensor systems, an...

  11. Passive Wireless Hydrogen Sensors Using Orthogonal Frequency Coded Acoustic Wave Devices Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes the development of passive surface acoustic wave (SAW) based hydrogen sensors for NASA application to distributed wireless hydrogen leak...

  12. Passive Wireless Hydrogen Sensors Using Orthogonal Frequency Coded Acoustic Wave Devices Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes the continued development of passive orthogonal frequency coded (OFC) surface acoustic wave (SAW) based hydrogen sensors for NASA application...

  13. DNA sensor cGAS-mediated immune recognition

    Directory of Open Access Journals (Sweden)

    Pengyan Xia

    2016-09-01

    Full Text Available Abstract The host takes use of pattern recognition receptors (PRRs to defend against pathogen invasion or cellular damage. Among microorganism-associated molecular patterns detected by host PRRs, nucleic acids derived from bacteria or viruses are tightly supervised, providing a fundamental mechanism of host defense. Pathogenic DNAs are supposed to be detected by DNA sensors that induce the activation of NFκB or TBK1-IRF3 pathway. DNA sensor cGAS is widely expressed in innate immune cells and is a key sensor of invading DNAs in several cell types. cGAS binds to DNA, followed by a conformational change that allows the synthesis of cyclic guanosine monophosphate–adenosine monophosphate (cGAMP from adenosine triphosphate and guanosine triphosphate. cGAMP is a strong activator of STING that can activate IRF3 and subsequent type I interferon production. Here we describe recent progresses in DNA sensors especially cGAS in the innate immune responses against pathogenic DNAs.

  14. Carbon nanotube gas sensor conductance model, sensing mechanism analysis, and applications in flexible sensors and wireless sensors

    Science.gov (United States)

    Ling, Yunfeng

    In this dissertation, the electrical property dependency of carbon nanotubes (CNTs) upon the humidity and chemical gas concentration is investigated. The electrical response of single-walled carbon nanotube (SWNT) networks to different humidity levels and gas molecules of ammonia (NH3) and nitrogen dioxide (NO2) at different concentrations was characterized by a sensor test system. In order to exclude the effect from contact resistance, the sheet resistance of SWNT networks was measured by transfer length method. The gas molecules concentration dependence of electrical property was analyzed, and two electrical models were proposed based on carrier transportation and adsorption isotherm respectively for different gas molecules. The electrical properties of SWNT networks estimated by the models were compared with the experimental data. The results show the models agree well with the experimental data. The primary objective of the sensor model is to understand the relationship between conductance of CNT networks and gas concentration. With this understanding, the model offers a precise measurement of the gas concentration based upon the electrical property of SWNT sensor. In addition, the mechanism of gas molecule adsorption on CNT networks is analyzed based on the conductance models. It is found that the conductance change of SWNT networks, induced by different humidity levels, is dominated by the thermal activation carrier hopping over the barriers between SWNTs. The average separation between the SWNTs increases linearly with the humidity levels. By contrast, when exposed to different NH3 and NO2, the conductance change is primarily determined by the charge transfer between gas molecules and CNTs. It shows that chemical molecules adsorption on the surface wall of SWNT causes the charge transfer. Furthermore, we investigated printed flexible electronics based on SWNTs and printable SWNT-based Frequency modulation (FM) passive wireless sensor tag on a flexible

  15. Zinc oxide nanowires on carbon microfiber as flexible gas sensor

    Science.gov (United States)

    Tonezzer, M.; Lacerda, R. G.

    2012-03-01

    In the past years, zinc oxide nanowires (ZnO NWs) have been proven to be an excellent material for gas sensors. In this work, we used ZnO nanowires in a novel architecture integrated on a carbon microfiber (μC) textile. This innovative design permits us to obtain mechanical flexibility, while the absence of any lithographic technique allows a large-area and low-cost fabrication of gas sensors. The performances of the devices are investigated for both oxidizing and reducing gases. The nano-on-micro structure of the sensor provides a high surface-to-volume ratio, leading to a fast and intense response for both oxygen (O2) and hydrogen (H2) gases. The sensor response has an optimum temperature condition at 280 °C with a response value of 10 for oxygen and 11 for hydrogen. The limit of detection (LoD) has been found to be 2 and 4 ppm for oxygen and hydrogen, respectively. Additionally, the sensor response and recovery time is small being less than 10 s for both O2 and H2.

  16. Flexible Graphene-Based Wearable Gas and Chemical Sensors.

    Science.gov (United States)

    Singh, Eric; Meyyappan, M; Nalwa, Hari Singh

    2017-10-11

    Wearable electronics is expected to be one of the most active research areas in the next decade; therefore, nanomaterials possessing high carrier mobility, optical transparency, mechanical robustness and flexibility, lightweight, and environmental stability will be in immense demand. Graphene is one of the nanomaterials that fulfill all these requirements, along with other inherently unique properties and convenience to fabricate into different morphological nanostructures, from atomically thin single layers to nanoribbons. Graphene-based materials have also been investigated in sensor technologies, from chemical sensing to detection of cancer biomarkers. The progress of graphene-based flexible gas and chemical sensors in terms of material preparation, sensor fabrication, and their performance are reviewed here. The article provides a brief introduction to graphene-based materials and their potential applications in flexible and stretchable wearable electronic devices. The role of graphene in fabricating flexible gas sensors for the detection of various hazardous gases, including nitrogen dioxide (NO 2 ), ammonia (NH 3 ), hydrogen (H 2 ), hydrogen sulfide (H 2 S), carbon dioxide (CO 2 ), sulfur dioxide (SO 2 ), and humidity in wearable technology, is discussed. In addition, applications of graphene-based materials are also summarized in detecting toxic heavy metal ions (Cd, Hg, Pb, Cr, Fe, Ni, Co, Cu, Ag), and volatile organic compounds (VOCs) including nitrobenzene, toluene, acetone, formaldehyde, amines, phenols, bisphenol A (BPA), explosives, chemical warfare agents, and environmental pollutants. The sensitivity, selectivity and strategies for excluding interferents are also discussed for graphene-based gas and chemical sensors. The challenges for developing future generation of flexible and stretchable sensors for wearable technology that would be usable for the Internet of Things (IoT) are also highlighted.

  17. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cardiopulmonary bypass in-line blood gas sensor... Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the level of gases in the blood. (b) Classification. Class II...

  18. High-sensitivity open-loop electronics for gravimetric acoustic-wave-based sensors.

    Science.gov (United States)

    Rabus, David; Friedt, Jean-Michel; Ballandras, Sylvain; Martin, Gilles; Carry, Emile; Blondeau-Patissier, Virginie

    2013-06-01

    Detecting chemical species in gas phase has recently received an increasing interest mainly for security control, trying to implement new systems allowing for extended dynamics and reactivity. In this work, an open-loop interrogation strategy is proposed to use radio-frequency acoustic transducers as micro-balances for that purpose. The resulting system is dedicated to the monitoring of chemical compounds in gaseous or liquid-phase state. A 16 Hz standard deviation is demonstrated at 125 MHz, with a working frequency band in the 60 to 133 MHz range, answering the requirements for using Rayleigh- and Love-wave-based delay lines operating with 40-μm acoustic wavelength transducers. Moreover, this electronic setup was used to interrogate a high-overtone bulk acoustic wave resonator (HBAR) microbalance, a new sensor class allowing for multi-mode interrogation for gravimetric measurement improvement. The noise source still limiting the system performance is due to the analog-to-digital converter of the microcontroller, thus leaving open degrees-of-freedom for improving the obtained results by optimizing the voltage reference and board layout. The operation of the system is illustrated using a calibrated galvanic deposition at the surface of Love-wave delay lines to assess theoretical predictions of their gravimetric sensitivity and to compare them with HBAR-based sensor sensitivity.

  19. Bedside arterial blood gas monitoring system using fluorescent optical sensors

    Science.gov (United States)

    Bartnik, Daniel J.; Rymut, Russell A.

    1995-05-01

    We describe a bedside arterial blood gas (ABG) monitoring system which uses fluorescent optical sensors in the measurement of blood pH, PCO2 and PO2. The Point-of-Care Arterial Blood Gas Monitoring System consists of the SensiCathTM optical sensor unit manufactured by Optical Sensors Incorporated and the TramTM Critical Care Monitoring System with ABG Module manufactured by Marquette Electronics Incorporated. Current blood gas measurement techniques require a blood sample to be removed from the patient and transported to an electrochemical analyzer for analysis. The ABG system does not require removal of blood from the patient or transport of the sample. The sensor is added to the patient's existing arterial line. ABG measurements are made by drawing a small blood sample from the arterial line in sufficient quantity to ensure an undiluted sample at the sensor. Measurements of pH, PCO2 and PO2 are made within 60 seconds. The blood is then returned to the patient, the line flushed and results appear on the bedside monitor. The ABG system offers several advantages over traditional electrochemical analyzers. Since the arterial line remains closed during the blood sampling procedure the patient's risk of infection is reduced and the caregiver's exposure to blood is eliminated. The single-use, disposable sensor can be measure 100 blood samples over 72 hours after a single two-point calibration. Quality Assurance checks are also available and provide the caregiver the ability to assess system performance even after the sensor is patient attached. The ABG module integrates with an existing bedside monitoring system. This allows ABG results to appear on the same display as ECG, respiration, blood pressure, cardiac output, SpO2, and other clinical information. The small module takes up little space in the crowded intensive care unit. Performance studies compare the ABG system with an electrochemical blood gas analyzer. Study results demonstrated accurate and precise blood

  20. Novel Modified Optical Fibers for High Temperature In-Situ Miniaturized Gas Sensors in Advanced Fossil Energy Systems

    Energy Technology Data Exchange (ETDEWEB)

    Pickrell, Gary [Virginia Polytechnic Institute & State University, Blacksburg, VA (United States); Scott, Brian [Virginia Polytechnic Institute & State University, Blacksburg, VA (United States)

    2014-06-30

    This report covers the technical progress on the program “Novel Modified Optical Fibers for High Temperature In-Situ Miniaturized Gas Sensors in Advanced Fossil Energy Systems”, funded by the National Energy Technology Laboratory of the U.S. Department of Energy, and performed by the Materials Science & Engineering and Electrical & Computer Engineering Departments at Virginia Tech, and summarizes technical progress from July 1st, 2005 –June 30th, 2014. The objective of this program was to develop novel fiber materials for high temperature gas sensors based on evanescent wave absorption in optical fibers. This project focused on two primary areas: the study of a sapphire photonic crystal fiber (SPCF) for operation at high temperature and long wavelengths, and a porous glass based fiber optic sensor for gas detection. The sapphire component of the project focused on the development of a sapphire photonic crystal fiber, modeling of the new structures, fabrication of the optimal structure, development of a long wavelength interrogation system, testing of the optical properties, and gas and temperature testing of the final sensor. The fabrication of the 6 rod SPCF gap bundle (diameter of 70μm) with a hollow core was successfully constructed with lead-in and lead-out 50μm diameter fiber along with transmission and gas detection testing. Testing of the sapphire photonic crystal fiber sensor capabilities with the developed long wavelength optical system showed the ability to detect CO2 at or below 1000ppm at temperatures up to 1000°C. Work on the porous glass sensor focused on the development of a porous clad solid core optical fiber, a hollow core waveguide, gas detection capabilities at room and high temperature, simultaneous gas species detection, suitable joining technologies for the lead-in and lead-out fibers and the porous sensor, sensor system sensitivity improvement, signal processing improvement, relationship between pore structure and fiber

  1. Surface modification of solid state gas sensors

    CERN Document Server

    Morris, L

    2000-01-01

    mechanism of the room temperature CO response of SnO sub 2 decorated with small Pt particles was refined. In this case Pt was applied by common impregnation techniques. The conductivity was shown to be controlled by the surface state of the Pt. The CO response at room temperature was found to be specific to the presence of Pt(ll) species. The mechanism was assigned to CO chemisorption onto Pt(ll), resulting in charge transfer, measured as conductivity increase. The samples were characterized by XPS, TPD, SEM, mass spectrometry and electrical measurements. Comparison of the results presented for Pt decorated BaSn sub 0 sub . sub 9 sub 7 Sb sub 0 sub . sub 0 sub 3 O sub 3 and BaFeO sub 3 demonstrated the phenomenon to be general providing that Pt particles act as surface traps, controlling the conductivity. The phenomenon of electrical conductivity being controlled by the chemical state of a surface grafted reactive centre, resulting in a room temperature gas response, is demonstrated. The reactive centres can ...

  2. Mid-Infrared Trace Gas Sensor Technology Based on Intracavity Quartz-Enhanced Photoacoustic Spectroscopy

    OpenAIRE

    Jacek Wojtas; Aleksander Gluszek; Arkadiusz Hudzikowski; Tittel, Frank K.

    2017-01-01

    The application of compact inexpensive trace gas sensor technology to a mid-infrared nitric oxide (NO) detectoion using intracavity quartz-enhanced photoacoustic spectroscopy (I-QEPAS) is reported. A minimum detection limit of 4.8 ppbv within a 30 ms integration time was demonstrated by using a room-temperature, continuous-wave, distributed-feedback quantum cascade laser (QCL) emitting at 5.263 µm (1900.08 cm−1) and a new compact design of a high-finesse bow-tie optical cavity with an integra...

  3. Long-Term Stability of Polymer-Coated Surface Transverse Wave Sensors for the Detection of Organic Solvent Vapors

    Directory of Open Access Journals (Sweden)

    Ullrich Stahl

    2017-11-01

    Full Text Available Arrays with polymer-coated acoustic sensors, such as surface acoustic wave (SAW and surface transverse wave (STW sensors, have successfully been applied for a variety of gas sensing applications. However, the stability of the sensors’ polymer coatings over a longer period of use has hardly been investigated. We used an array of eight STW resonator sensors coated with different polymers. This sensor array was used at semi-annual intervals for a three-year period to detect organic solvent vapors of three different chemical classes: a halogenated hydrocarbon (chloroform, an aliphatic hydrocarbon (octane, and an aromatic hydrocarbon (xylene. The sensor signals were evaluated with regard to absolute signal shifts and normalized signal shifts leading to signal patterns characteristic of the respective solvent vapors. No significant time-related changes of sensor signals or signal patterns were observed, i.e., the polymer coatings kept their performance during the course of the study. Therefore, the polymer-coated STW sensors proved to be robust devices which can be used for detecting organic solvent vapors both qualitatively and quantitatively for several years.

  4. Tailored ramp wave generation in gas gun experiments

    Directory of Open Access Journals (Sweden)

    Cotton Matthew

    2015-01-01

    Full Text Available Gas guns are traditionally used as platforms to introduce a planar shock wave to a material using plate impact methods, generating states on the Hugoniot. The ability to deliver a ramp wave to a target during a gas gun experiment enables access to different regions of the equation-of-state surface, making it a valuable technique for characterising material behaviour. Previous techniques have relied on the use of multi-material impactors to generate a density gradient, which can be complex to manufacture. In this paper we describe the use of an additively manufactured steel component consisting of an array of tapered spikes which can deliver a ramp wave over ∼ 2 μs. The ability to tailor the input wave by varying the component design is discussed, an approach which makes use of the design freedom offered by additive manufacturing techniques to rapidly iterate the spike profile. Results from gas gun experiments are presented to evaluate the technique, and compared with 3D hydrodynamic simulations.

  5. Feasibility of Passive Gas Sensor Based on Whispering Gallery Modes and its RADAR Interrogation: Theoretical and Experimental Investigations

    Directory of Open Access Journals (Sweden)

    Hamida HALLIL

    2010-05-01

    Full Text Available Feasibility of gas sensors based on Titanium Dioxide (TiO2 dielectric resonator operating with whispering-gallery modes is presented. The gas or humidity adsorption modifies the TiO2 dielectric permittivity and such modification induces variation in the resonant frequencies of high-Q whispering-gallery modes in the millimeter-wave frequency range. Full-wave electromagnetic simulation indicates that the measurement of this variation allows the derivation of few pars-per-million fluctuations in gas or humidity concentration. For validation purposes very first prototypes of resonator operating with whispering-gallery modes in the millimeter-wave frequency range are micro-machined. The obtained measured performances confirm that such high-Q resonant modes are very sensitive to small variations in dielectric resonator permittivity. Moreover we validate experimentally that these small variations can be remotely detected from the RADAR interrogation of an antenna loaded by the whispering-gallery modes resonator.

  6. Surface acoustic wave devices as passive buried sensors

    Science.gov (United States)

    Friedt, J.-M.; Rétornaz, T.; Alzuaga, S.; Baron, T.; Martin, G.; Laroche, T.; Ballandras, S.; Griselin, M.; Simonnet, J.-P.

    2011-02-01

    Surface acoustic wave (SAW) devices are currently used as passive remote-controlled sensors for measuring various physical quantities through a wireless link. Among the two main classes of designs—resonator and delay line—the former has the advantage of providing narrow-band spectrum informations and hence appears compatible with an interrogation strategy complying with Industry-Scientific-Medical regulations in radio-frequency (rf) bands centered around 434, 866, or 915 MHz. Delay-line based sensors require larger bandwidths as they consists of a few interdigitated electrodes excited by short rf pulses with large instantaneous energy and short response delays but is compatible with existing equipment such as ground penetrating radar (GPR). We here demonstrate the measurement of temperature using the two configurations, particularly for long term monitoring using sensors buried in soil. Although we have demonstrated long term stability and robustness of packaged resonators and signal to noise ratio compatible with the expected application, the interrogation range (maximum 80 cm) is insufficient for most geology or geophysical purposes. We then focus on the use of delay lines, as the corresponding interrogation method is similar to the one used by GPR which allows for rf penetration distances ranging from a few meters to tens of meters and which operates in the lower rf range, depending on soil water content, permittivity, and conductivity. Assuming propagation losses in a pure dielectric medium with negligible conductivity (snow or ice), an interrogation distance of about 40 m is predicted, which overcomes the observed limits met when using interrogation methods specifically developed for wireless SAW sensors, and could partly comply with the above-mentioned applications. Although quite optimistic, this estimate is consistent with the signal to noise ratio observed during an experimental demonstration of the interrogation of a delay line buried at a depth of 5

  7. Laser deposition of sulfonated phthalocyanines for gas sensors

    Czech Academy of Sciences Publication Activity Database

    Fitl, Přemysl; Vrňata, M.; Kopecký, D.; Vlček, J.; Škodová, J.; Bulíř, Jiří; Novotný, Michal; Pokorný, Petr

    2014-01-01

    Roč. 302, MAY (2014), s. 37-41 ISSN 0169-4332. [European-Materials-Research-Society Symposium on Laser Material Interactions for Micro- and Nano- Applications /5./. Strasbourg, 27.05.2013-31.05.2013] R&D Projects: GA ČR(CZ) GAP108/11/1298 Institutional support: RVO:68378271 Keywords : Matrix Assisted Pulsed Laser Evaporation * substituted phthalocyanine s * gas sensors * impedance measurements Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.711, year: 2014

  8. Graphene nanomesh as highly sensitive chemiresistor gas sensor

    Science.gov (United States)

    Paul, Rajat Kanti; Badhulika, Sushmee; Saucedo, Nuvia M.; Mulchandani, Ashok

    2016-01-01

    Graphene is a one atom thick carbon allotrope with all surface atoms that has attracted significant attention as a promising material as the conduction channel of a field-effect transistor and chemical field-effect transistor sensors. However, the zero bandgap of semimetal graphene still limits its application for these devices. In this work, ethanol-chemical vapor deposition (CVD) grown p-type semiconducting large-area monolayer graphene film was patterned into nanomesh by the combination of nanosphere lithography and reactive ion etching and evaluated as field-effect transistor and chemiresistor gas sensors. The resulting neck-width of the synthesized nanomesh was about ~20 nm comprised of the gap between polystyrene spheres that was formed during the reactive ion etching process. The neck-width and the periodicities of the graphene nanomesh could be easily controlled depending the duration/power of RIE and the size of PS nanospheres. The fabricated GNM transistor device exhibited promising electronic properties featuring high drive current and ION/IOFF ratio of about 6, significantly higher than its film counterpart. Similarly, when applied as chemiresistor gas sensor at room temperature, the graphene nanomesh sensor showed excellent sensitivity towards NO2 and NH3, significantly higher than their film counterparts. The ethanol-based graphene nanomesh sensors exhibited sensitivities of about 4.32%/ppm in NO2 and 0.71%/ppm in NH3 with limit of detections of 15 ppb and 160 ppb, respectively. Our demonstrated studies on controlling the neck width of the nanomesh would lead to further improvement of graphene-based transistors and sensors. PMID:22931286

  9. Integrated Micro-Machined Hydrogen Gas Sensor. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Frank DiMeo, Jr.

    2000-10-02

    This report details our recent progress in developing novel MEMS (Micro-Electro-Mechanical Systems) based hydrogen gas sensors. These sensors couple novel thin films as the active layer on a device structure known as a Micro-HotPlate. This coupling has resulted in a gas sensor that has several unique advantages in terms of speed, sensitivity, stability and amenability to large scale manufacture. This Phase-I research effort was focused on achieving the following three objectives: (1) Investigation of sensor fabrication parameters and their effects on sensor performance. (2) Hydrogen response testing of these sensors in wet/dry and oxygen-containing/oxygen-deficient atmospheres. (3) Investigation of the long-term stability of these thin film materials and identification of limiting factors. We have made substantial progress toward achieving each of these objectives, and highlights of our phase I results include the demonstration of signal responses with and without oxygen present, as well as in air with a high level of humidity. We have measured response times of <0.5 s to 1% H{sub 2} in air, and shown the ability to detect concentrations of <200 ppm. These results are extremely encouraging and suggest that this technology has substantial potential for meeting the needs of a hydrogen based economy. These achievements demonstrate the feasibility of using micro-hotplates structures in conjunction with palladium+coated metal-hydride films for sensing hydrogen in many of the environments required by a hydrogen based energy economy. Based on these findings, they propose to continue and expand the development of this technology in Phase II.

  10. The elastic wave velocity response of methane gas hydrate formation in vertical gas migration systems

    Science.gov (United States)

    Bu, Q. T.; Hu, G. W.; Ye, Y. G.; Liu, C. L.; Li, C. F.; Best, A. I.; Wang, J. S.

    2017-06-01

    Knowledge of the elastic wave velocities of hydrate-bearing sediments is important for geophysical exploration and resource evaluation. Methane gas migration processes play an important role in geological hydrate accumulation systems, whether on the seafloor or in terrestrial permafrost regions, and their impact on elastic wave velocities in sediments needs further study. Hence, a high-pressure laboratory apparatus was developed to simulate natural continuous vertical migration of methane gas through sediments. Hydrate saturation (S h) and ultrasonic P- and S-wave velocities (V p and V s) were measured synchronously by time domain reflectometry (TDR) and by ultrasonic transmission methods respectively during gas hydrate formation in sediments. The results were compared to previously published laboratory data obtained in a static closed system. This indicated that the velocities of hydrate-bearing sediments in vertical gas migration systems are slightly lower than those in closed systems during hydrate formation. While velocities increase at a constant rate with hydrate saturation in the closed system, P-wave velocities show a fast-slow-fast variation with increasing hydrate saturation in the vertical gas migration system. The observed velocities are well described by an effective-medium velocity model, from which changing hydrate morphology was inferred to cause the fast-slow-fast velocity response in the gas migration system. Hydrate forms firstly at the grain contacts as cement, then grows within the pore space (floating), then finally grows into contact with the pore walls again. We conclude that hydrate morphology is the key factor that influences the elastic wave velocity response of methane gas hydrate formation in vertical gas migration systems.

  11. Inhomogeneous Oxygen Vacancy Distribution in Semiconductor Gas Sensors: Formation, Migration and Determination on Gas Sensing Characteristics

    OpenAIRE

    Liu, Jianqiao; Gao, Yinglin; Wu, Xu; Jin, Guohua; Zhai, Zhaoxia; Liu, Huan

    2017-01-01

    The density of oxygen vacancies in semiconductor gas sensors was often assumed to be identical throughout the grain in the numerical discussion of the gas-sensing mechanism of the devices. In contrast, the actual devices had grains with inhomogeneous distribution of oxygen vacancy under non-ideal conditions. This conflict between reality and discussion drove us to study the formation and migration of the oxygen defects in semiconductor grains. A model of the gradient-distributed oxygen vacanc...

  12. Organic Membranes for Selectivity Enhancement of Metal Oxide Gas Sensors

    Directory of Open Access Journals (Sweden)

    Thorsten Graunke

    2016-01-01

    Full Text Available We present the characterization of organic polyolefin and thermoplastic membranes for the enhancement of the selectivity of metal oxide (MOX gas sensors. The experimental study is done based on theoretical considerations of the membrane characteristics. Through a broad screening of dense symmetric homo- and copolymers with different functional groups, the intrinsic properties such as the mobility or the transport of gases through the matrix were examined in detail. A subset of application-relevant gases was chosen for the experimental part of the study: H2, CH4, CO, CO2, NO2, ethanol, acetone, acetaldehyde, and water vapor. The gases have similar kinetic diameters and are therefore difficult to separate but have different functional groups and polarity. The concentration of the gases was based on the international indicative limit values (TWA, STEL. From the results, a simple relationship was to be found to estimate the permeability of various polar and nonpolar gases through gas permeation (GP membranes. We used a broadband metal oxide gas sensor with a sensitive layer made of tin oxide with palladium catalyst (SnO2:Pd. Our aim was to develop a low-cost symmetrical dense polymer membrane to selectively detect gases with a MOX sensor.

  13. Implementation of a quantum cascade laser-based gas sensor prototype for sub-ppmv H2S measurements in a petrochemical process gas stream

    OpenAIRE

    Moser, Harald; P?lz, Walter; Waclawek, Johannes Paul; Ofner, Johannes; Lendl, Bernhard

    2016-01-01

    The implementation of a sensitive and selective as well as industrial fit gas sensor prototype based on wavelength modulation spectroscopy with second harmonic detection (2f-WMS) employing an 8-?m continuous-wave distributed feedback quantum cascade laser (CW-DFB-QCL) for monitoring hydrogen sulfide (H2S) at sub-ppm levels is reported. Regarding the applicability for analytical and industrial process purposes aimed at petrochemical environments, a synthetic methane (CH4) matrix of up to 1000?...

  14. A STUDY OF NONLINEAR PHENOMENA IN THE PROPAGATION OF ELECTROMAGNETIC WAVES IN A WEAKLY IONIZED GAS.

    Science.gov (United States)

    This paper is a study of nonlinear phenomena in the propagation of electromagnetic waves in a weakly ionized gas externally biased with a magneto...static field. The present study is restricted to the nonlinear phenomena arising from the interaction of electromagnetic waves in the ionized gas. The...the propagation of electromagnetic waves in the ionized gas, and also on the reflection of waves from an ionized gas semi-infinite extent. (Author)

  15. Gas Sensors Based on Ceramic p-n Heterocontacts

    Energy Technology Data Exchange (ETDEWEB)

    Aygun, Seymen Murat [Iowa State Univ., Ames, IA (United States)

    2005-01-01

    with very high forward currents. Ga doped heterocontacts showed the highest sensitivity observed during current-time measurements as well, even though the sensor response was rather slow. Finally, a possible synergistic effect of doping both p and n-sides was studied by utilizing current-time measurements for 1.5 mol% Ni-CuO/1.5 mol% Ga-ZnO heterocontact. A sensitivity value of ~5.1 was obtained with the fastest response among all the samples. The time needed to reach 90% coverage was lowered by a factor of 4 when compared to the pure heterocontact and the time needed to reach 70% coverage was just over one minute. Heterocontact gas sensors are promising candidates for high temperature sensor applications. Today, Si-based microelectromechanical system (MEMS) technology has shown great promise for developing novel devices such as pressure sensors, chemical sensors, and temperature sensors through complex designs. However, the harsh thermal, vibrational, and corrosive environments common to many aerospace applications impose severe limitations on their use. Sensors based on ceramic p-n heterocontacts are promising alternatives because of their inherent corrosion resistance and environmental stability. The other advantages include their inherent tuning ability to differentiate between different reducing gases and a possible cost efficient production of a wireless sensor. Being a capacitive type sensor, its output can be transformed into a passive wireless device by creating a tuned LC circuit. In this way, the sensor output (the capacitance) can be accessed remotely by measuring the resonant frequency. The relatively simple structure of heterocontacts makes it suitable for thick film fabrication techniques to make sensor packages.

  16. Development of fiber optic sensors at TNO for explosion and shock wave measurements

    NARCIS (Netherlands)

    Cheng, L.K.; Smorenburg, C.; Bree, J.L.M.J. van; Bouma, R.H.B.; Meer, B.J. van der; Prinse, W.C.; Scholtes, J.H.G.

    2000-01-01

    Fiber Optic sensors are found to be very suitable for explosion and shock wave measurements because they are immune to Electromagnetic Interference (EMI). In the past few years, TNO has developed a number of sensor systems for explosion and shock wave measurements in which the optical fiber is a

  17. Trace Detection of Pentaerythritol Tetranitrate Using Electrochemical Gas Sensors

    Directory of Open Access Journals (Sweden)

    Praveen K. Sekhar

    2014-01-01

    Full Text Available Selective and sensitive detection of trace amounts of pentaerythritol tetranitrate (PETN is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensor as the detector. A single sensor is operated in the dominant hydrocarbon (HC and nitrogen oxides (NOx mode by varying the sensor operating condition. The potentiometric sensor with integrated heaters was used to capture the signature of PETN. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (10 μg down to 200 ng. The ratio of the HC integrated peak area to the NOx integrated peak area is identified as an indicator of selectivity. The HC/NOx ratio is unique for PETN and has a range from 1.7 to 2.7. This detection technique has the potential to become an orthogonal technique to the existing explosive screening technologies for reducing the number of false positives/false negatives in a cost-effective manner.

  18. Carbon Nanotubes as Active Components for Gas Sensors

    Directory of Open Access Journals (Sweden)

    Wei-De Zhang

    2009-01-01

    Full Text Available The unique structure of carbon nanotubes endows them with fantastic physical and chemical characteristics. Carbon nanotubes have been widely studied due to their potential applications in many fields including conductive and high-strength composites, energy storage and energy conversion devices, sensors, field emission displays and radiation sources, hydrogen storage media, and nanometer-sized semiconductor devices, probes, and quantum wires. Some of these applications have been realized in products, while others show great potentials. The development of carbon nanotubes-based sensors has attracted intensive interest in the last several years because of their excellent sensing properties such as high selectivity and prompt response. Carbon nanotube-based gas sensors are summarized in this paper. Sensors based on single-walled, multiwalled, and well-aligned carbon nanotubes arrays are introduced. Modification of carbon nanotubes with functional groups, metals, oxides, polymers, or doping carbon nanotubes with other elements to enhance the response and selectivity of the sensors is also discussed.

  19. Mid- infrared semiconductor laser based trace gas sensor technologies for environmental monitoring and industrial process control

    Science.gov (United States)

    Lewicki, Rafał; Jahjah, Mohammad; Ma, Yufei; Tittel, Frank K.; Stefanski, Przemyslaw; Tarka, Jan

    2013-01-01

    Recent advances in the development of compact sensors based on mid-infrared continuous wave (CW), thermoelectrically cooled (TEC) and room temperature operated quantum cascade lasers (QCLs) for the detection, quantification and monitoring of trace gas species and their applications in environmental and industrial process analysis will be reported. These sensors employ a 2f wavelength modulation (WM) technique based on quartz enhanced photoacoustic spectroscopy (QEPAS) that achieves detection sensitivity at the ppb and sub ppb concentration levels. The merits of QEPAS include an ultra-compact, rugged sensing module, with wide dynamic range and immunity to environmental acoustic noise. QCLs are convenient QEPAS excitation sources that permit the targeting of strong fundamental rotational-vibrational transitions which are one to two orders of magnitude more intense in the mid-infrared than overtone transitions in the near infrared spectral region.

  20. Chemical detection demonstrated using an evanescent wave graphene optical sensor

    Energy Technology Data Exchange (ETDEWEB)

    Maliakal, Ashok; Reith, Leslie; Cabot, Steve [LGS Innovations, 15 Vreeland Rd., Florham Park, New Jersey 07932 (United States)

    2016-04-11

    Graphene devices have been constructed on silicon mirrors, and the graphene is optically probed through an evanescent wave interaction in an attenuated total reflectance configuration using an infrared spectrometer. The graphene is electrically biased in order to tune its optical properties. Exposure of the device to the chemicals iodine and ammonia causes observable and reversible changes to graphene's optical absorption spectra in the mid to near infrared range which can be utilized for the purpose of sensing. Electrical current measurements through the graphene are made simultaneously with optical measurements allowing for simultaneous sensing using two separate detection modalities. Our current results reveal sub-ppm detection limits for iodine and approximately 100 ppm detection limits for ammonia. We have also demonstrated that this approach will work at 1.55 μm, which opens up the possibility for graphene optical sensors that leverage commercial telecom light sources.

  1. Photonic crystal wave guide for non-cryogenic cooled carbon nanotube based middle wave infrared sensors

    Science.gov (United States)

    Fung, Carmen Kar Man; Xi, Ning; Lou, Jianyong; Lai, King Wai Chiu; Chen, Hongzhi

    2010-10-01

    We report high sensitivity carbon nanotube (CNT) based middle wave infrared (MWIR) sensors with a two-dimensional photonic crystal waveguide. MWIR sensors are of great importance in a variety of current military applications including ballistic missile defense, surveillance and target detection. Unlike other existing MWIR sensing materials, CNTs exhibit low noise level and can be used as new nano sensing materials for MWIR detection where cryogenic cooling is not required. However, the quantum efficiency of the CNT based infrared sensor is still limited by the small sensing area and low incoming electric field. Here, a photonic nanostructure is used as a resonant cavity for boosting the electric field intensity at the position of the CNT sensing element. A two-dimensional photonic crystal with periodic holes in a polymer thin film is fabricated and a resonant cavity is formed by removing holes from the array of the photonic crystal. Based on the design of the photonic crystal topologies, we theoretically study the electric field distribution to predict the resonant behavior of the structure. Numerical simulations reveal the field is enhanced and almost fully confined to the defect region of the photonic crystal. To verify the electric field enhancement effect, experiments are also performed to measure the photocurrent response of the sensor with and without the photonic crystal resonant cavity. Experimental results show that the photocurrent increases ~3 times after adding the photonic crystal resonant cavity.

  2. Pollution Monitoring System Using Gas Sensor based on Wireless Sensor Network

    Directory of Open Access Journals (Sweden)

    M. Udin Harun Al Rasyid

    2016-01-01

    Full Text Available Carbon monoxide (CO and carbon dioxide (CO2 gases are classified as colorless and odorless gas so we need special tools to monitor their concentration in the air. Concentration of air pollution of CO and CO2 that are high in the air will give serious effects for health status. CO is a poisonous gas that damages the circulation of oxygen in the blood when inhaled, while CO2 is one of the gases that causes global warming. In this paper, we developed an integrated pollution monitoring (IPOM system to monitor the concentration of air pollution. This research implemented three sensor nodes (end-device which each node contains CO and CO2 sensors on the gas sensors board to perform sensing from the environment. Furthermore, the data taken from the environment by the sensor will be sent to the meshlium gateway using IEEE 802.15.4 Zigbee communications and processed by the gateway in order to be sent to the computer server. The data is stored in meshlium gateway using MySQL database as a backup, and it will be synchronized to the MySQL database in the computer server. We provide services for public to access the information in database server through a desktop and website application.

  3. On Mass Loading and Dissipation Measured with Acoustic Wave Sensors: A Review

    Directory of Open Access Journals (Sweden)

    Marina V. Voinova

    2009-01-01

    Full Text Available We summarize current trends in the analysis of physical properties (surface mass density, viscosity, elasticity, friction, and charge of various thin films measured with a solid-state sensor oscillating in a gaseous or liquid environment. We cover three different types of mechanically oscillating sensors: the quartz crystal microbalance with dissipation (QCM-D monitoring, surface acoustic wave (SAW, resonators and magnetoelastic sensors (MESs. The fourth class of novel acoustic wave (AW mass sensors, namely thin-film bulk acoustic resonators (TFBARs on vibrating membranes is discussed in brief. The paper contains a survey of theoretical results and practical applications of the sensors and includes a comprehensive bibliography.

  4. Utilizing the response patterns of a temperature modulated chemoresistive gas sensor for gas diagnosis

    Energy Technology Data Exchange (ETDEWEB)

    Amini, Amir [Jannatabad College, Sama Organization, Islamic Azad University, Tehran (Iran, Islamic Republic of); Ghafarinia, Vahid, E-mail: amir.amini.elec@gmail.com, E-mail: ghafarinia@ee.kntu.ac.ir [Electrical Engineering Department, K. N. Toosi University of Technology, Tehran (Iran, Islamic Republic of)

    2011-02-15

    The observed features in the temporal response patterns of a temperature-modulated chemoresistive gas sensor were used for gas diagnosis. The patterns were recorded for clean air and air contaminated with different levels of some volatile organic compounds while a staircase heating voltage waveform had been applied to the microheater of a tin oxide gas sensor that modulated its operating temperature. Combining the steady-state and transient parameters of the recorded responses in the 50-400 deg. C range resulted in discriminatory feature vectors which were utilized for contaminant classification. The information content of these feature vectors was proved sufficient for discrimination of methanol, ethanol, 1-butanol, and acetone contaminations in a wide concentration range.

  5. Hollow Waveguide Gas Sensor for Mid-Infrared Trace Gas Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S; Young, C; Chan, J; Carter, C; Mizaikoff, B

    2007-07-12

    A hollow waveguide mid-infrared gas sensor operating from 1000 cm{sup -1} to 4000 cm{sup -1} has been developed, optimized, and its performance characterized by combining a FT-IR spectrometer with Ag/Ag-halide hollow core optical fibers. The hollow core waveguide simultaneously serves as a light guide and miniature gas cell. CH{sub 4} was used as test analyte during exponential dilution experiments for accurate determination of the achievable limit of detection (LOD). It is shown that the optimized integration of an optical gas sensor module with FT-IR spectroscopy provides trace sensitivity at the few hundreds of parts-per-billion concentration range (ppb, v/v) for CH{sub 4}.

  6. Gas Sensors Based on Semiconducting Metal Oxide One-Dimensional Nanostructures

    Directory of Open Access Journals (Sweden)

    Jin Huang

    2009-12-01

    Full Text Available This article provides a comprehensive review of recent (2008 and 2009 progress in gas sensors based on semiconducting metal oxide one-dimensional (1D nanostructures. During last few years, gas sensors based on semiconducting oxide 1D nanostructures have been widely investigated. Additionally, modified or doped oxide nanowires/nanobelts have also been synthesized and used for gas sensor applications. Moreover, novel device structures such as electronic noses and low power consumption self-heated gas sensors have been invented and their gas sensing performance has also been evaluated. Finally, we also point out some challenges for future investigation and practical application.

  7. Au nanoparticles improve amorphous carbon to be gas sensors

    Science.gov (United States)

    Liu, Keng-Wen; Lee, Jian-Heng; Chou, Hsiung; Lin, Tzu-Ching; Lin, Si-Ting; Shih-Jye Sun Collaboration

    In order to make the amorphous carbon possess the gas sensing capability transferring some sp3 orbits to sp2 is necessary. It is proposed that the metallic materials having a large charge exchange with sp3 carbon orbits are being catalysts to transfer the carbon orbits. We found embedding gold nanoparticles to the amorphous carbon will induce many compact sp2 orbits around the nanoparticles, which make the amorphous carbon be the candidate material for the gas sensors. The orbits of amorphous carbon near the interface of Au nanoparticles can be changed from sp3 to compact sp2 to reduce the surface energy of Au nanoparticles. Meanwhile, our molecular dynamics simulation has confirmed the fact, when an Au nanoparticle is embedded in the amorphous carbon system the ratio of sp2 orbits increases dramatically. Similar results also have been confirmed from the Raman spectrum measurements. We controlled the carrier transport by changing the hopping barriers formed by amorphous carbon matrix between the Au nanoparticles to modify the resistance. These nanocomposites exhibit a superior sensitivity to NH3 at room temperature as well as good reproducibility and short response/recovery times, which could have potential applications in gas sensors. Dept. of Applied Physics,NUK, Kaohsiung, Taiwan.

  8. Device optimization of CO2 gas sensor using planar technology.

    Science.gov (United States)

    Lee, Woon Young; Choi, Yong Kook; Satyanarayana, L; Park, Jin Seong

    2007-11-01

    A planar type Li+ ion based potentiometric CO2 micro gas sensor of size 2 x 3 mm has been fabricated on alumina substrate by combining thin and thick film technology. The heater, electrodes and electrolyte were deposited by thin film deposition technique and the sensing and reference electrodes were printed by silk screen printing technology. The optimal thickness and sintering temperature of electrolyte are 1.2 microm and 775 degrees C. The sensor with Li2CO3 and 20 mol% BaCO3 not only exhibits a good Nernstian behavior but also consistent results over a long time at 450 degrees C in dry as well as 70% RH humidity condition between 160-5000 ppm CO2 concentrations. The spreading effect of the sensing and reference materials was controlled by the addition of Al2O3:B2O3 (1:2 mol%) glass.

  9. Portable multi-sensor system for gas detection using the temporal window technique; Systeme multicapteurs de detection de gaz, portable, utilisant la technique du fenetrage temporel

    Energy Technology Data Exchange (ETDEWEB)

    Cazaubon, Ch. [Bordeaux-1 Univ., CRED, 33 - Talence (France); Levi, H.; Bordieu, Ch.; Rebiere, D.; Pistre, J. [Bordeaux-1 Univ., Lab. IXL, UMR CNRS 5818, 33 (France)

    1999-07-01

    An autonomous and portable multi-sensor system was constructed. It can drive four gas sensors (surface acoustic waves. SAW. for examples) and four voltage output gas sensors (semiconductor metal oxide sensors, for example). Two micro-controllers. MC68HC11F1 and MC68HC711E9, used as master and slave respectively, are mounted on two cards. The first card contains the signal processing treatment algorithm using a neural network and a shifting temporal window technique: it allows real time gas selection. The second card insure the overall temperature control by an auto-adaptive PID. GB gas SAW responses were applied to the device in order to test his performances. (authors)

  10. Data-driven modeling of nano-nose gas sensor arrays

    DEFF Research Database (Denmark)

    Alstrøm, Tommy Sonne; Larsen, Jan; Nielsen, Claus Højgård

    2010-01-01

    We present a data-driven approach to classification of Quartz Crystal Microbalance (QCM) sensor data. The sensor is a nano-nose gas sensor that detects concentrations of analytes down to ppm levels using plasma polymorized coatings. Each sensor experiment takes approximately one hour hence...

  11. Optical Breath Gas Sensor for Extravehicular Activity Application

    Science.gov (United States)

    Wood, William R.; Casias, Miguel E.; Vakhtin, Andrei B.; Pilgrim, Jeffrey S> Chullen, Cinda; Falconi, Eric A.

    2012-01-01

    The function of the infrared gas transducer used during extravehicular activity (EVA) in the current space suit is to measure and report the concentration of carbon dioxide (CO2) in the ventilation loop. The next generation Portable Life Support System (PLSS) requires next generation CO2 sensing technology with performance beyond that presently in use on the Shuttle/International Space Station extravehicular mobility unit (EMU). Accommodation within space suits demands that optical sensors meet stringent size, weight, and power requirements. A laser diode (LD) spectrometer based on wavelength modulation spectroscopy (WMS) is being developed for this purpose by Vista Photonics, Inc. Two prototype devices were delivered to NASA Johnson Space Center (JSC) in September 2011. The sensors incorporate a laser diode based CO2 channel that also includes an incidental water vapor (humidity) measurement and a separate oxygen (O2) channel using a vertical cavity surface emitting laser (VCSEL). Both prototypes are controlled digitally with a field-programmable gate array (FPGA)/microcontroller architecture. Based on the results of the initial instrument development, further prototype development and testing of instruments leveraging the lessons learned were desired. The present development extends and upgrades the earlier hardware to the Advanced PLSS 2.0 test article being constructed and tested at JSC. Various improvements to the electronics and gas sampling are being advanced by this project. The combination of low power electronics with the performance of a long wavelength laser spectrometer enables multi-gas sensors with significantly increased performance over that presently offered in the EMU. .

  12. Fabrication of a P3HT-ZnO Nanowires Gas Sensor Detecting Ammonia Gas

    Directory of Open Access Journals (Sweden)

    Chin-Guo Kuo

    2017-12-01

    Full Text Available In this study, an organic-inorganic semiconductor gas sensor was fabricated to detect ammonia gas. An inorganic semiconductor was a zinc oxide (ZnO nanowire array produced by atomic layer deposition (ALD while an organic material was a p-type semiconductor, poly(3-hexylthiophene (P3HT. P3HT was suitable for the gas sensing application due to its high hole mobility, good stability, and good electrical conductivity. In this work, P3HT was coated on the zinc oxide nanowires by the spin coating to form an organic-inorganic heterogeneous interface of the gas sensor for detecting ammonia gas. The thicknesses of the P3HT were around 462 nm, 397 nm, and 277 nm when the speeds of the spin coating were 4000 rpm, 5000 rpm, and 6000 rpm, respectively. The electrical properties and sensing characteristics of the gas sensing device at room temperature were evaluated by Hall effect measurement and the sensitivity of detecting ammonia gas. The results of Hall effect measurement for the P3HT-ZnO nanowires semiconductor with 462 nm P3HT film showed that the carrier concentration and the mobility were 2.7 × 1019 cm−3 and 24.7 cm2∙V−1∙s−1 respectively. The gas sensing device prepared by the P3HT-ZnO nanowires semiconductor had better sensitivity than the device composed of the ZnO film and P3HT film. Additionally, this gas sensing device could reach a maximum sensitivity around 11.58 per ppm.

  13. Theoretical Modeling and Implementation of Traveling Wave Sensor Based on PCB Coils

    Directory of Open Access Journals (Sweden)

    Zewen Li

    2015-01-01

    Full Text Available Based on analyzing characteristics of Rogowski coil, a new type of PCB traveling wave sensor with simple structure, high linearity, and anti-interference ability is proposed. The sensor has fine physical structure, which can effectively resist external electromagnetic interference by anti-interference measurement. In addition, it can greatly improve mutual inductance based on simple combinations. Simulations show that the new PCB traveling wave sensor can validly extract and deliver traveling wave signal and therefore realize fault location and protection accurately.

  14. Fault detection, isolation, and diagnosis of status self-validating gas sensor arrays.

    Science.gov (United States)

    Chen, Yin-Sheng; Xu, Yong-Hui; Yang, Jing-Li; Shi, Zhen; Jiang, Shou-da; Wang, Qi

    2016-04-01

    The traditional gas sensor array has been viewed as a simple apparatus for information acquisition in chemosensory systems. Gas sensor arrays frequently undergo impairments in the form of sensor failures that cause significant deterioration of the performance of previously trained pattern recognition models. Reliability monitoring of gas sensor arrays is a challenging and critical issue in the chemosensory system. Because of its importance, we design and implement a status self-validating gas sensor array prototype to enhance the reliability of its measurements. A novel fault detection, isolation, and diagnosis (FDID) strategy is presented in this paper. The principal component analysis-based multivariate statistical process monitoring model can effectively perform fault detection by using the squared prediction error statistic and can locate the faulty sensor in the gas sensor array by using the variables contribution plot. The signal features of gas sensor arrays for different fault modes are extracted by using ensemble empirical mode decomposition (EEMD) coupled with sample entropy (SampEn). The EEMD is applied to adaptively decompose the original gas sensor signals into a finite number of intrinsic mode functions (IMFs) and a residual. The SampEn values of each IMF and the residual are calculated to reveal the multi-scale intrinsic characteristics of the faulty sensor signals. Sparse representation-based classification is introduced to identify the sensor fault type for the purpose of diagnosing deterioration in the gas sensor array. The performance of the proposed strategy is compared with other different diagnostic approaches, and it is fully evaluated in a real status self-validating gas sensor array experimental system. The experimental results demonstrate that the proposed strategy provides an excellent solution to the FDID of status self-validating gas sensor arrays.

  15. IMPLEMENTATION OF SELF DIAGNOSTIC AND INTELLIGENT POWER MANAGEMENT PROTOCOLS ON WIRELESS GAS SENSOR NODE

    OpenAIRE

    Dipanjan Bhattacharjee,; Sushabhan Choudhury

    2011-01-01

    This paper presents implementation of self diagnostic, power management protocols and hardware design to enhance the hardware flexibility and sensing accuracy of sensor node. We have come withsolutions for various design challenges faced on gas sensor. The embedded intelligent protocols over comes the problems of heater voltage dependency on gas sensors. Here we deal with sensors which arecapable of detecting different part per million (ppm) of gases. The main aim of the work is to implement ...

  16. Screen printed metal oxide gas sensors with microminiature gas separation systems

    Energy Technology Data Exchange (ETDEWEB)

    Pratt, K.; King, C. [Capteur Sensors and Analysers, Didcot, Oxon (United Kingdom)

    2001-07-01

    An active area of research is that of microminiature chemical analysis systems, also known as 'micro total analysis systems' ({mu}-TAS). Such systems may incorporate sampling, separation, microreactors and analysis devices onto micromachined substrates. Gas sensitive resistors based on semiconducting metal oxides are readily fabricated using conventional thick film ceramic processes. Partial selectivity towards target gases is achieved by tailoring the properties of the sensing material. In this paper we describe novel devices which combine many of the attributes of {mu}-TAS systems with metal oxide gas sensors, while being manufacturable by screen printing onto alumina substrates, without requiring complex micromachining or etching processes. (orig.)

  17. Plasma and wave phenomena induced by neutral gas releases in the solar wind

    Directory of Open Access Journals (Sweden)

    H. Laakso

    2002-01-01

    Full Text Available We investigate plasma and wave disturbances generated by nitrogen (N2 gas releases from the cooling system of an IR-camera on board the Vega 1 and Vega 2 spacecraft, during their flybys of comet Halley in March 1986. N2 molecules are ionized by solar UV radiation at a rate of ~ 7 · 10-7 s-1 and give rise to a plasma cloud expanding around the spacecraft. Strong disturbances due to the interaction of the solar wind with the N+2 ion cloud are observed with a plasma and wave experiment (APV-V instrument. Three gas releases are accompanied by increases in cold electron density and simultaneous decreases of the spacecraft potential; this study shows that the spacecraft potential can be monitored with a reference sensor mounted on a short boom. The comparison between the model and observations suggests that the gas expands as an exhaust plume, and approximately only 1% of the ions can escape the beam within the first meters. The releases are also associated with significant increases in wave electric field emission (8 Hz–300 kHz; this phenomenon lasts for more than one hour after the end of the release, which is most likely due to the temporary contamination of the spacecraft surface by nitrogen gas. DC electric fields associated with the events are complex but interesting. No magnetic field perturbations are detected, suggesting that no significant diamagnetic effect (i.e. magnetic cavity is associated with these events.Key words. Ionosphere (planetary ionosphere – Space plasma physics (active perturbation experiments; instruments and techniques

  18. Plasma and wave phenomena induced by neutral gas releases in the solar wind

    Directory of Open Access Journals (Sweden)

    H. Laakso

    Full Text Available We investigate plasma and wave disturbances generated by nitrogen (N2 gas releases from the cooling system of an IR-camera on board the Vega 1 and Vega 2 spacecraft, during their flybys of comet Halley in March 1986. N2 molecules are ionized by solar UV radiation at a rate of ~ 7 · 10-7 s-1 and give rise to a plasma cloud expanding around the spacecraft. Strong disturbances due to the interaction of the solar wind with the N+2 ion cloud are observed with a plasma and wave experiment (APV-V instrument. Three gas releases are accompanied by increases in cold electron density and simultaneous decreases of the spacecraft potential; this study shows that the spacecraft potential can be monitored with a reference sensor mounted on a short boom. The comparison between the model and observations suggests that the gas expands as an exhaust plume, and approximately only 1% of the ions can escape the beam within the first meters. The releases are also associated with significant increases in wave electric field emission (8 Hz–300 kHz; this phenomenon lasts for more than one hour after the end of the release, which is most likely due to the temporary contamination of the spacecraft surface by nitrogen gas. DC electric fields associated with the events are complex but interesting. No magnetic field perturbations are detected, suggesting that no significant diamagnetic effect (i.e. magnetic cavity is associated with these events.

    Key words. Ionosphere (planetary ionosphere – Space plasma physics (active perturbation experiments; instruments and techniques

  19. Low power gas sensor array on flexible acetate substrate

    Science.gov (United States)

    Benedict, Samatha; Basu, Palash Kumar; Bhat, Navakanta

    2017-07-01

    In this paper, we present a novel approach of fabricating a low-cost and low power gas sensor array on flexible acetate sheets for sensing CO, SO2, H2 and NO2 gases. The array has four sensor elements with an integrated microheater which can be individually controlled enabling the monitoring of four gases. The thermal properties of the microheater characterized by IR imaging are presented. The microheater with an active area of 15 µm  ×  5 µm reaches a temperature of 300 °C, consuming 2 mW power, the lowest reported on flexible substrates. A sensing electrode is patterned on top of the microheater, and a nanogap (100 nm) is created by an electromigration process. This nanogap is bridged by four sensing materials doped with platinum, deposited using a solution dispensing technique. The sensing material characterization is completed using energy dispersive x-ray analysis. The sensing characteristics of ZnO for CO, V2O5 for SO2, SnO2 for H2 and WO3 for NO2 gases are studied at different microheater voltages. The sensing characteristics of ZnO at different bending angles is also studied, which shows that the microheater and the sensing material are intact without any breaking upto a bending angle of 20°. The ZnO CO sensor shows sensitivity of 146.2% at 1 ppm with good selectivity.

  20. Analysis of nanowire transistor based nitrogen dioxide gas sensor – A simulation study

    Directory of Open Access Journals (Sweden)

    Gaurav Saxena

    2015-06-01

    Full Text Available Sensors sensitivity, selectivity and stability has always been a prime design concern for gas sensors designers. Modeling and simulation of gas sensors aids the designers in improving their performance. In this paper, different routes for the modeling and simulation of a semiconducting gas sensor is presented. Subsequently, by employing one of the route, the response of Zinc Oxide nanowire transistor towards nitrogen dioxide ambient is simulated. In addition to the sensing mechanism, simulation study of gas species desorption by applying a recovery voltage is also presented.

  1. Inhomogeneous Oxygen Vacancy Distribution in Semiconductor Gas Sensors: Formation, Migration and Determination on Gas Sensing Characteristics

    Science.gov (United States)

    Liu, Jianqiao; Gao, Yinglin; Wu, Xu; Jin, Guohua; Zhai, Zhaoxia; Liu, Huan

    2017-01-01

    The density of oxygen vacancies in semiconductor gas sensors was often assumed to be identical throughout the grain in the numerical discussion of the gas-sensing mechanism of the devices. In contrast, the actual devices had grains with inhomogeneous distribution of oxygen vacancy under non-ideal conditions. This conflict between reality and discussion drove us to study the formation and migration of the oxygen defects in semiconductor grains. A model of the gradient-distributed oxygen vacancy was proposed based on the effects of cooling rate and re-annealing on semiconductive thin films. The model established the diffusion equations of oxygen vacancy according to the defect kinetics of diffusion and exclusion. We described that the steady-state and transient-state oxygen vacancy distributions, which were used to calculate the gas-sensing characteristics of the sensor resistance and response to reducing gases under two different conditions. The gradient-distributed oxygen vacancy model had the applications in simulating the sensor performances, such as the power law, the grain size effect and the effect of depletion layer width. PMID:28796167

  2. Inhomogeneous Oxygen Vacancy Distribution in Semiconductor Gas Sensors: Formation, Migration and Determination on Gas Sensing Characteristics

    Directory of Open Access Journals (Sweden)

    Jianqiao Liu

    2017-08-01

    Full Text Available The density of oxygen vacancies in semiconductor gas sensors was often assumed to be identical throughout the grain in the numerical discussion of the gas-sensing mechanism of the devices. In contrast, the actual devices had grains with inhomogeneous distribution of oxygen vacancy under non-ideal conditions. This conflict between reality and discussion drove us to study the formation and migration of the oxygen defects in semiconductor grains. A model of the gradient-distributed oxygen vacancy was proposed based on the effects of cooling rate and re-annealing on semiconductive thin films. The model established the diffusion equations of oxygen vacancy according to the defect kinetics of diffusion and exclusion. We described that the steady-state and transient-state oxygen vacancy distributions, which were used to calculate the gas-sensing characteristics of the sensor resistance and response to reducing gases under two different conditions. The gradient-distributed oxygen vacancy model had the applications in simulating the sensor performances, such as the power law, the grain size effect and the effect of depletion layer width.

  3. Inhomogeneous Oxygen Vacancy Distribution in Semiconductor Gas Sensors: Formation, Migration and Determination on Gas Sensing Characteristics.

    Science.gov (United States)

    Liu, Jianqiao; Gao, Yinglin; Wu, Xu; Jin, Guohua; Zhai, Zhaoxia; Liu, Huan

    2017-08-10

    The density of oxygen vacancies in semiconductor gas sensors was often assumed to be identical throughout the grain in the numerical discussion of the gas-sensing mechanism of the devices. In contrast, the actual devices had grains with inhomogeneous distribution of oxygen vacancy under non-ideal conditions. This conflict between reality and discussion drove us to study the formation and migration of the oxygen defects in semiconductor grains. A model of the gradient-distributed oxygen vacancy was proposed based on the effects of cooling rate and re-annealing on semiconductive thin films. The model established the diffusion equations of oxygen vacancy according to the defect kinetics of diffusion and exclusion. We described that the steady-state and transient-state oxygen vacancy distributions, which were used to calculate the gas-sensing characteristics of the sensor resistance and response to reducing gases under two different conditions. The gradient-distributed oxygen vacancy model had the applications in simulating the sensor performances, such as the power law, the grain size effect and the effect of depletion layer width.

  4. Comparison of information content of temporal response of chemoresistive gas sensor under three different temperature modulation regimes for gas detection of different feature reduction methods

    Science.gov (United States)

    Hosseini-Golgoo, S. M.; Salimi, F.; Saberkari, A.; Rahbarpour, S.

    2017-12-01

    In the present work the feature extraction of transient response of a resistive gas sensor under temperature cycling, temperature transient, and temperature combination methods were compared. So, the heater were stimulated by three pulse (cycling), ramp (transient) and staircase (combination) waveforms. The period or duration of all waves was equal to 40 s. Methanol, ethanol, 1-propanol, 1-butanol, toluene and acetone each at 11 different concentration levels in the range of 100 to 2000 ppm were used as the target gases. The utilized sensor was TGS-813 that made by Figaro Company. Recorded results were studied and heuristic features such as peak, rise time, slope and curvature of recorded responses were extracted for each heater waveform. Results showed that although application of this feature extraction method to all waveforms led to gas diagnoses, best results were achieved in the case of staircase waveform. The combination waveform had enough information to separate all examined target gases.

  5. Passive Wireless Cryogenic Liquid Level Sensors Using Orthogonal Frequency Coded Acoustic Wave Devices Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes the continued development of passive wireless surface acoustic wave (SAW) based liquid level sensors for NASA application to cryogenic liquid...

  6. Passive Wireless Cryogenic Liquid Level Sensors Using Orthogonal Frequency Coded Acoustic Wave Devices Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes the development of passive wireless surface acoustic wave (SAW) based liquid level sensors for NASA application to cryogenic liquid level...

  7. Cognitive sensor networks for structure defect monitoring and classification using guided wave signals

    Science.gov (United States)

    Jin, Yuanwei; O'Donoughue, Nicholas; Moura, José M. F.; Harley, Joel; Garrett, James H.; Oppenheim, Irving J.; Soibelman, Lucio; Ying, Yujie; He, Lin

    2010-04-01

    This paper develops a framework of a cognitive sensor networks system for structure defect monitoring and classification using guided wave signals. Guided ultrasonic waves that can propagate long distances along civil structures have been widely studied for inspection and detection of structure damage. Smart ultrasonic sensors arranged as a spatially distributed cognitive sensor networks system can transmit and receive ultrasonic guided waves to interrogate structure defects such as cracks and corrosion. A distinguishing characteristic of the cognitive sensor networks system is that it adaptively probes and learns about the environment, which enables constant optimization in response to its changing understanding of the defect response. In this paper, we develop a sequential multiple hypothesis testing scheme combined with adaptive waveform transmission for defect monitoring and classification. The performance is verified using numerical simulations of guided elastic wave propagation on a pipe model and by Monte Carlo simulations for computing the probability of correct classification.

  8. Self-Activated Transparent All-Graphene Gas Sensor with Endurance to Humidity and Mechanical Bending.

    Science.gov (United States)

    Kim, Yeon Hoo; Kim, Sang Jin; Kim, Yong-Jin; Shim, Yeong-Seok; Kim, Soo Young; Hong, Byung Hee; Jang, Ho Won

    2015-10-27

    Graphene is considered as one of leading candidates for gas sensor applications in the Internet of Things owing to its unique properties such as high sensitivity to gas adsorption, transparency, and flexibility. We present self-activated operation of all graphene gas sensors with high transparency and flexibility. The all-graphene gas sensors which consist of graphene for both sensor electrodes and active sensing area exhibit highly sensitive, selective, and reversible responses to NO2 without external heating. The sensors show reliable operation under high humidity conditions and bending strain. In addition to these remarkable device performances, the significantly facile fabrication process enlarges the potential of the all-graphene gas sensors for use in the Internet of Things and wearable electronics.

  9. SnO2/PPy Screen-Printed Multilayer CO2 Gas Sensor

    Directory of Open Access Journals (Sweden)

    S.A. WAGHULEY

    2007-05-01

    Full Text Available Tin dioxide (SnO2 plays a dominant role in solid state gas sensors and exhibit sensitivity towards oxidizing and reducing gases by a variation of its electrical properties. The electrical conducting polymer-polypyrrole (PPy has high anisotropy of electrical conduction and used as a gas sensor. SnO2/PPy multilayer, pure SnO2, pure PPy sensors were prepared by screen-printing method on Al2O3 layer followed by glass substrate. The sensors were used for different concentration (ppm of CO2 gas investigation at room temperature (303 K. The sensitivity of SnO2/PPy multilayer sensor was found to be higher, compared with pure SnO2 and pure PPy sensors. The multilayer sensor exhibited improved stability. The response and recovery time of multilayer sensor were found to be ~2 min and ~10 min respectively.

  10. Metal Oxide Gas Sensors, a Survey of Selectivity Issues Addressed at the SENSOR Lab, Brescia (Italy).

    Science.gov (United States)

    Ponzoni, Andrea; Baratto, Camilla; Cattabiani, Nicola; Falasconi, Matteo; Galstyan, Vardan; Nunez-Carmona, Estefania; Rigoni, Federica; Sberveglieri, Veronica; Zambotti, Giulia; Zappa, Dario

    2017-03-29

    This work reports the recent results achieved at the SENSOR Lab, Brescia (Italy) to address the selectivity of metal oxide based gas sensors. In particular, two main strategies are being developed for this purpose: (i) investigating different sensing mechanisms featuring different response spectra that may be potentially integrated in a single device; (ii) exploiting the electronic nose (EN) approach. The former has been addressed only recently and activities are mainly focused on determining the most suitable configuration and measurements to exploit the novel mechanism. Devices suitable to exploit optical (photoluminescence), magnetic (magneto-optical Kerr effect) and surface ionization in addition to the traditional chemiresistor device are here discussed together with the sensing performance measured so far. The electronic nose is a much more consolidated technology, and results are shown concerning its suitability to respond to industrial and societal needs in the fields of food quality control and detection of microbial activity in human sweat.

  11. Metal Oxide Gas Sensors, a Survey of Selectivity Issues Addressed at the SENSOR Lab, Brescia (Italy

    Directory of Open Access Journals (Sweden)

    Andrea Ponzoni

    2017-03-01

    Full Text Available This work reports the recent results achieved at the SENSOR Lab, Brescia (Italy to address the selectivity of metal oxide based gas sensors. In particular, two main strategies are being developed for this purpose: (i investigating different sensing mechanisms featuring different response spectra that may be potentially integrated in a single device; (ii exploiting the electronic nose (EN approach. The former has been addressed only recently and activities are mainly focused on determining the most suitable configuration and measurements to exploit the novel mechanism. Devices suitable to exploit optical (photoluminescence, magnetic (magneto-optical Kerr effect and surface ionization in addition to the traditional chemiresistor device are here discussed together with the sensing performance measured so far. The electronic nose is a much more consolidated technology, and results are shown concerning its suitability to respond to industrial and societal needs in the fields of food quality control and detection of microbial activity in human sweat.

  12. Wide Bandgap Semiconductor Nanorod and Thin Film Gas Sensors

    Directory of Open Access Journals (Sweden)

    Stepehn J. Pearton

    2006-06-01

    Full Text Available In this review we discuss the advances in use of GaN and ZnO-based solid-statesensors for gas sensing applications. AlGaN/GaN high electron mobility transistors(HEMTs show a strong dependence of source/drain current on the piezoelectricpolarization -induced two dimensional electron gas (2DEG. Furthermore, spontaneous andpiezoelectric polarization induced surface and interface charges can be used to develop verysensitive but robust sensors for the detection of gases. Pt-gated GaN Schottky diodes and Sc2O3/AlGaN/GaN metal-oxide semiconductor diodes also show large change in forwardcurrents upon exposure to H2 containing ambients. Of particular interest are methods fordetecting ethylene (C2H4, which offers problems because of its strong double bonds andhence the difficulty in dissociating it at modest temperatures. ZnO nanorods offer largesurface area, are bio-safe and offer excellent gas sensing characteristics.

  13. Sensitivity analysis of P-waves and S-waves to gas hydrate in the Shenhu area using OBS

    Science.gov (United States)

    Xing, Lei; Liu, Xueqin; Zhang, Jin; Liu, Huaishan; Zhang, Jing; Li, Zizheng; Wang, Jianhua

    2018-02-01

    Compared to towed streamers, ocean-bottom seismometers (OBS) obtain both S-wave data and richer wavefield information. In this paper, the induced polarization method is used to conduct wavefield separation on OBS data obtained from the Shenhu area in the South China Sea. A comparison of the changes in P- and S-waves, and a comprehensive analysis of geological factors within the area, enable analysis and description of the occurrence of natural gas hydrate in the study area. Results show an increase in P-wave velocity when natural gas hydrate exists in the formation, whereas the S-wave velocity remains almost constant, as S-waves can only propagate through the rock skeleton. Therefore, the bottom-simulating reflection (BSR) response of the P-wave is better than that of the S-wave in the frequency analysis profile. In a wide-angle section, the refractive wave of the hydrate layer is evident when using P-wave components but identification is difficult with S-wave components. This velocity model illustrates the sensitivity of P- and S-wave components to gas hydrate. The use of this polarization method and results of analysis provide technical and theoretical support for research on hydrate deposits and other geological features in the Shenhu area.

  14. Chemoresistive Gas Sensors for the Detection of Colorectal Cancer Biomarkers

    Directory of Open Access Journals (Sweden)

    Cesare Malagù

    2014-10-01

    Full Text Available Numerous medical studies show that tumor growth is accompanied by protein changes that may lead to the peroxidation of the cell membrane with consequent emission of volatile organic compounds (VOCs by breath or intestinal gases that should be seen as biomarkers for colorectal cancer (CRC. The analysis of VOCs represents a non-invasive and potentially inexpensive preliminary screening technique. An array of chemoresistive gas sensors based on screen-printed metal oxide semiconducting films has been selected to discriminate gases of oncological interest, e.g., 1-iodononane and benzene, widely assumed to be biomarkers of colorectal cancer, from those of interference in the gut, such as methane and nitric oxide.

  15. Mid-Infrared Trace Gas Sensor Technology Based on Intracavity Quartz-Enhanced Photoacoustic Spectroscopy

    Directory of Open Access Journals (Sweden)

    Jacek Wojtas

    2017-03-01

    Full Text Available The application of compact inexpensive trace gas sensor technology to a mid-infrared nitric oxide (NO detectoion using intracavity quartz-enhanced photoacoustic spectroscopy (I-QEPAS is reported. A minimum detection limit of 4.8 ppbv within a 30 ms integration time was demonstrated by using a room-temperature, continuous-wave, distributed-feedback quantum cascade laser (QCL emitting at 5.263 µm (1900.08 cm−1 and a new compact design of a high-finesse bow-tie optical cavity with an integrated resonant quartz tuning fork (QTF. The optimum configuration of the bow-tie cavity was simulated using custom software. Measurements were performed with a wavelength modulation scheme (WM using a 2f detection procedure.

  16. Mid-Infrared Trace Gas Sensor Technology Based on Intracavity Quartz-Enhanced Photoacoustic Spectroscopy.

    Science.gov (United States)

    Wojtas, Jacek; Gluszek, Aleksander; Hudzikowski, Arkadiusz; Tittel, Frank K

    2017-03-04

    The application of compact inexpensive trace gas sensor technology to a mid-infrared nitric oxide (NO) detectoion using intracavity quartz-enhanced photoacoustic spectroscopy (I-QEPAS) is reported. A minimum detection limit of 4.8 ppbv within a 30 ms integration time was demonstrated by using a room-temperature, continuous-wave, distributed-feedback quantum cascade laser (QCL) emitting at 5.263 µm (1900.08 cm-1) and a new compact design of a high-finesse bow-tie optical cavity with an integrated resonant quartz tuning fork (QTF). The optimum configuration of the bow-tie cavity was simulated using custom software. Measurements were performed with a wavelength modulation scheme (WM) using a 2f detection procedure.

  17. Digital Architecture for a Trace Gas Sensor Platform

    Science.gov (United States)

    Gonzales, Paula; Casias, Miguel; Vakhtin, Andrei; Pilgrim, Jeffrey

    2012-01-01

    A digital architecture has been implemented for a trace gas sensor platform, as a companion to standard analog control electronics, which accommodates optical absorption whose fractional absorbance equivalent would result in excess error if assumed to be linear. In cases where the absorption (1-transmission) is not equivalent to the fractional absorbance within a few percent error, it is necessary to accommodate the actual measured absorption while reporting the measured concentration of a target analyte with reasonable accuracy. This requires incorporation of programmable intelligence into the sensor platform so that flexible interpretation of the acquired data may be accomplished. Several different digital component architectures were tested and implemented. Commercial off-the-shelf digital electronics including data acquisition cards (DAQs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), and microcontrollers have been used to achieve the desired outcome. The most completely integrated architecture achieved during the project used the CPLD along with a microcontroller. The CPLD provides the initial digital demodulation of the raw sensor signal, and then communicates over a parallel communications interface with a microcontroller. The microcontroller analyzes the digital signal from the CPLD, and applies a non-linear correction obtained through extensive data analysis at the various relevant EVA operating pressures. The microcontroller then presents the quantitatively accurate carbon dioxide partial pressure regardless of optical density. This technique could extend the linear dynamic range of typical absorption spectrometers, particularly those whose low end noise equivalent absorbance is below one-part-in-100,000. In the EVA application, it allows introduction of a path-length-enhancing architecture whose optical interference effects are well understood and quantified without sacrificing the dynamic range that allows

  18. Ammonia gas sensing property of gadolinium oxide using fiber optic gas sensor

    Science.gov (United States)

    Kumar, J. Santhosh; Ranganathan, B.; Sastikumar, D.

    2017-05-01

    The design of fiber optic sensor is based on a cladding modification methodology. A fiber-optic chemical sensor is developed by replacing a certain portion of the original cladding with a chemically sensitive material, specifically, calcinated gadolinium oxide (Gd2O3).Both the light absorption co-efficient and refractive index change upon exposure to chemical vapours of volatile organic compounds (VOCs) such as ammonia (NH3), ethanol (CH3CH2OH), and methanol (CH3OH). The spectral characteristics of the sensor were studied for different concentrations ranging from 0-500 ppm. These changes induced the optical intensity modulation of the transmitted optical signal. During interaction between the sensing material and VOCs, the output intensity is taken into account to detect the toxic VOCs present in the environment. This was systematically investigated by X-ray diffractometer (XRD) and SEM. The XRD analysis indicated that the calcinated Gd2O3 was formed in cubic structure with the crystallite size of 13 nm. The Gd2O3 nanorods with thickness ranging from 80 to 120 nm were confirmed from SEM. The ammonia gas response of the Gd2O3 sensor is presented. A model is proposed for understanding the spectral intensity variations.

  19. SENSOR GAS BERBASIS FILM TIPIS DENGAN KONFIGURASI TRANSISTOR EFEK MEDAN (FET UNTUK DETEKSI GAS CO

    Directory of Open Access Journals (Sweden)

    Sujarwata Sujarwata

    2013-02-01

    Full Text Available Pembuatan dan karakterisasi Transistor Efek Medan (FET berbasis film tipis dengan struktur bottom-contact dan panjang channel 100 ?m untuk aplikasi sensor gas. Pembuatan FET dengan cara: permulaan dilakukan pencucian substrat Si/SiO 2 dengan etanol dalam ultrasonic cleaner, kemudian dilakukan pendeposisian elektroda source/ drain dengan metode penguapan hampa udara dan teknik lithography. Selanjutnya dilakukan deposisi film tipis CuPc diantara source/drain sebagai panjang channel dan elektrode gate. Karakteristik FET, untuk daerah aktif untuk V DS (2,80 s/d 3,42 V dan kuat arus I (0,00095 s/d 0,00169 A. FET akan aktif beroperasi hanya diperlukan tegangan V DS (2,79 V s/d 3,43 V dan dengan ukuran sangat kecil ( 1,5 mm x 3,1 mm serta jarak antara S ke D adalah 100 ?m. Aplikasi sensor gas telah dilakukan untuk mendeteksi gas CO, diperoleh hasil untuk response time 90 detik dan recovery time 120 detik. DS

  20. Fiber optic gas sensors with vanadium oxide and tungsten oxide nanoparticle coated claddings

    Science.gov (United States)

    Renganathan, B.; Sastikumar, D.; Raj, S. Gokul; Ganesan, A. R.

    2014-03-01

    Fiber optic gas sensors with nanoparticles of V2O5 and WO3 as the cladding of a PMMA fiber have been proposed in this work. The spectral response of these sensors for detection of ammonia, methanol and ethanol under various concentrations has been studied at room temperature. The time response characteristics of the sensors are also presented.

  1. Laboratory Connections: Gas Monitoring Transducers: Relative Humidity Sensors.

    Science.gov (United States)

    Powers, Michael H.; Hull, Stacey E.

    1988-01-01

    Explains the operation of five relative humidity sensors: psychrometer, hair hygrometer, resistance hygrometer, capacitance hygrometer, and resistance-capacitance hygrometer. Outlines the theory behind the electronic sensors and gives computer interfacing information. Lists sensor responses for calibration. (MVL)

  2. Unipolar and Bipolar High-Magnetic-Field Sensors Based on Surface Acoustic Wave Resonators

    Science.gov (United States)

    Polewczyk, V.; Dumesnil, K.; Lacour, D.; Moutaouekkil, M.; Mjahed, H.; Tiercelin, N.; Petit Watelot, S.; Mishra, H.; Dusch, Y.; Hage-Ali, S.; Elmazria, O.; Montaigne, F.; Talbi, A.; Bou Matar, O.; Hehn, M.

    2017-08-01

    While surface acoustic wave (SAW) sensors have been used to measure temperature, pressure, strains, and low magnetic fields, the capability to measure bipolar fields and high fields is lacking. In this paper, we report magnetic surface acoustic wave sensors that consist of interdigital transducers made of a single magnetostrictive material, either Ni or TbFe2 , or based on exchange-biased (Co /IrMn ) multilayers. By controlling the ferromagnet magnetic properties, high-field sensors can be obtained with unipolar or bipolar responses. The issue of hysteretic response of the ferromagnetic material is especially addressed, and the control of the magnetic properties ensures the reversible behavior in the SAW response.

  3. Millenium Sensor Systems (MISSY). Project: Modular microsystem process for gas sensorics. Final report; Millenium Sensor Systems (MISSY). Teilvorhaben: Modular aufgebauter Mikrosystembaukasten fuer die Gassensorik. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, G.; Friedberger, A.; Becker, T.; Bosch-von Braunmuehl, C.; Rose, E.; Ahlers, S.; Kreisl, P.; Schalwig, J.

    2003-07-01

    Low-power Hotplate arrays for use as substrates for gas sensor elements have been created using a new SOI (SOI: silicon on insulator) technology. The developed arrays feature a very low power consumption which is about an order of magnitude lower than that of comparable commercially available sensor elements, which is about 0.5-1W. The employed SOI technology allows single crystal structures with a high degree of thermal insulation to be suspended within a very stable chip frame. Contrary to nitride membrane technology which has been developed prior to the project, the SOI hotplates enable the integration of gas sensitive MOS (MOS: metal oxide semiconductor) devices with a catalytically active platinum gate. A modular process build with a separation into 'silicon front-end' and sensor-specific 'back-end' parts allows a relatively cheap industrial teamwork between silicon foundries and sensor developers. In the framework of the back-end process a set of gas sensitive layers were developed and through extensive gas measurements a sensor database was generated. In order to allow a quick and easy application adaptation a software tool was developed which makes use of this sensor database and allows to tune the operation parameters of the sensors to the application at hand. The possibility to integrate gas sensor elements with distinct cross sensitivities into the hotplates facilitates the realization of application-specific arrays for wide range of possible applications. Along those lines small, chip-integrated micro gas sensor arrays were created that possessed enhanced selectivity compared to a single commercial sensor element while staying within the power consumption budget of the commercial sensor. Particular applications of the developed technology were demonstrated within EADS as well as together with project partners. Among those were air pollution monitoring and fire detection. (orig.)

  4. Highly Sensitive and Selective VOC Sensor Systems Based on Semiconductor Gas Sensors: How to?

    Directory of Open Access Journals (Sweden)

    Andreas Schütze

    2017-03-01

    Full Text Available Monitoring of volatile organic compounds (VOCs is of increasing importance in many application fields such as environmental monitoring, indoor air quality, industrial safety, fire detection, and health applications. The challenges in all of these applications are the wide variety and low concentrations of target molecules combined with the complex matrix containing many inorganic and organic interferents. This paper will give an overview over the application fields and address the requirements, pitfalls, and possible solutions for using low-cost sensor systems for VOC monitoring. The focus lies on highly sensitive metal oxide semiconductor gas sensors, which show very high sensitivity, but normally lack selectivity required for targeting relevant VOC monitoring applications. In addition to providing an overview of methods to increase the selectivity, especially virtual multisensors achieved with dynamic operation, and boost the sensitivity further via novel pro-concentrator concepts, we will also address the requirement for high-performance gas test systems, advanced solutions for operating and read-out electronic, and, finally, a cost-efficient factory and on-site calibration. The various methods will be primarily discussed in the context of requirements for monitoring of indoor air quality, but can equally be applied for environmental monitoring and other fields.

  5. Multifunctional potentiometric gas sensor array with an integrated temperature control and temperature sensors

    Science.gov (United States)

    Blackburn, Bryan M; Wachsman, Eric D

    2015-05-12

    Embodiments of the subject invention relate to a gas sensor and method for sensing one or more gases. An embodiment incorporates an array of sensing electrodes maintained at similar or different temperatures, such that the sensitivity and species selectivity of the device can be fine tuned between different pairs of sensing electrodes. A specific embodiment pertains to a gas sensor array for monitoring combustion exhausts and/or chemical reaction byproducts. An embodiment of the subject device related to this invention operates at high temperatures and can withstand harsh chemical environments. Embodiments of the device are made on a single substrate. The devices can also be made on individual substrates and monitored individually as if they were part of an array on a single substrate. The device can incorporate sensing electrodes in the same environment, which allows the electrodes to be coplanar and, thus, keep manufacturing costs low. Embodiments of the device can provide improvements to sensitivity, selectivity, and signal interference via surface temperature control.

  6. Improving the sensitivity of the ZnO gas sensor to dimethyl sulfide

    Science.gov (United States)

    Suchorska-Woźniak, P.; Nawrot, W.; Rac, O.; Fiedot, M.; Teterycz, H.

    2016-01-01

    This study was focused on how to improve the gas sensing properties of resistive gas sensors based on zinc oxide to dimethyl sulfide (DMS). The aim of this research was to investigate possible ways of improvement detection of dimethyl sulfide, such as volume doping with synthesized gold nanoparticles or applying sepiolite passive filter. The addition of noble metal into the gas sensing layer is a widely known method of increasing gas sensor response. Sepiolite is a clay mineral with highly porous structure consisting of nanotubes few micrometers long and water absorption abilities. In this work thick-film resistive gas sensors based on zinc oxide were made (pure ZnO, modified by gold nanoparticles, with the addition of filter) and tested for low concentration (2 ppm) of dimethyl sulfide. The sensitivities to DMS of developed sensors were compared. Attention was paid to the analysis of the impact of high humidity (90% RH) on the sensor time response.

  7. A Review on Innovative Procedures for the Analysis of Data from Gas Sensor Systems and Networks

    Directory of Open Access Journals (Sweden)

    Rolf Seifert

    2015-01-01

    Full Text Available Economic online and in-situ field analyses applications like discriminated alarming of smoldering fire or toxic gas leakages, monitoring of volatile components in chemical and biochemical processes, quality monitoring in food processing etc., wait for reliable and economic analytical solutions by sensor systems. This paper presents various innovative mathematical procedures to analyze data from gas sensor systems and gas sensor nets: ProSens - an efficient mathematical procedure for calibration and evaluation of tin oxide gas sensor data, SimSens – a mathematical program for simultaneous analysis of gases, ProCal - a program for batch-wise calibration of multi gas sensors and ProSource - a procedure for source localization. Applications to real data demonstrate the performance of the procedures.

  8. Sensor Data Qualification Technique Applied to Gas Turbine Engines

    Science.gov (United States)

    Csank, Jeffrey T.; Simon, Donald L.

    2013-01-01

    This paper applies a previously developed sensor data qualification technique to a commercial aircraft engine simulation known as the Commercial Modular Aero-Propulsion System Simulation 40,000 (C-MAPSS40k). The sensor data qualification technique is designed to detect, isolate, and accommodate faulty sensor measurements. It features sensor networks, which group various sensors together and relies on an empirically derived analytical model to relate the sensor measurements. Relationships between all member sensors of the network are analyzed to detect and isolate any faulty sensor within the network.

  9. Study on the inside gas flow visualization of oxygen sensor cover; Kashika ni yoru O2 sensor cover nai no gas nagare hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Hocho, S.; Mitsuishi, Y.; Inagaki, M. [Nippon Soken, Inc., Tokyo (Japan); Hamaguchi, S.; Mizusawa, K. [Toyota Motor Corp., Aichi (Japan)

    1997-10-01

    In order to make clear the difference of the response time between the oxygen sensors with different protection covers, we visualized gas flow inside of sensor covers by means of two experimental methods: One is `Smoke Suspension Method` using liquid paraffin vapor as the smoke. With smoke suspension method, we detected the streamlines inside of the covers. The other is `Color Reaction Method` using the reaction of phenolphthalein and NH3 gas. With color reaction method, we confirmed the streamline inside of the cover and furthermore detected the difference of the response time of each sensor. 3 refs., 7 figs., 1 tab.

  10. A sparse sensor network topologized for cylindrical wave-based identification of damage in pipeline structures

    Science.gov (United States)

    Wang, Qiang; Hong, Ming; Su, Zhongqing

    2016-07-01

    A sparse sensor network, based on the concept of semi-decentralized and standardized sensing, is developed, to actively excite and acquire cylindrical waves for damage identification and health monitoring of pipe structures. Differentiating itself from conventional ‘ring-style’ transducer arrays which attempt to steer longitudinal axisymmetric cylindrical waves via transducer synchronism, this sparse sensor network shows advantages in some aspects, including the use of fewer sensors, simpler manipulation, quicker configuration, less mutual dependence among sensors, and an improved signal-to-noise ratio. The sparse network is expanded topologically, aimed at eliminating the presence of ‘blind zones’ and the challenges associated with multi-path propagation of cylindrical waves. Theoretical analysis is implemented to comprehend propagation characteristics of waves guided by a cylindrical structure. A probability-based diagnostic imaging algorithm is introduced to visualize damage in pixelated images in an intuitive, prompt, and automatic manner. A self-contained health monitoring system is configured for experimental validation, via which quantitative identification of mono- and multi-damage in a steel cylinder is demonstrated. The results highlight an expanded sensing coverage of the sparse sensor network and its enhanced capacity of acquiring rich information, avoiding the cost of augmenting the number of sensors in a sensor network.

  11. Gas-sensing enhancement methods for hydrothermal synthesized SnO2 based sensors.

    Science.gov (United States)

    Zhao, Yalei; Zhang, Wenlong; Yang, Bin; Liu, Jingquan; Chen, Xiang; Wang, Xiaolin; Yang, Chunsheng

    2017-08-16

    The gas sensing enhancement methods for hydrothermal synthesized SnO2-based gas sensors could be performed from three areas: structural improvement, composition optimization and processing improvement, which were aimed to improve the performance of the gas sensors. There was 0-D, 1-D and 3-D structures reported in literatures. Controllable synthesis of different structures was deployed to increase specific surface area. Change of composition would intensively tailor the SnO2 structure, which affected the gas sensing performance. Besides, doping and compounding methods were adopted to promote gas-sensing performance by adjusting surface condition of SnO2 crystal and constructing heterojunction. As for processing area, it was very important to find the optimal reaction time and temperature. In this paper, gas-solid reaction rate constant was proposed to evaluate gas-sensing property and find the excellent hydrothermal synthesized SnO2-based gas sensor at present. © 2017 IOP Publishing Ltd.

  12. Shock wave deformation of a nonspherical gas bubble in liquids

    Science.gov (United States)

    Hasegawa, T.; Fujiwara, T.; Itoh, H.

    The deformation of a nonspherical gas bubble caused by the incidence of a shock wave is analysed, taking account of both the nonspherical initial shape and the suddenly induced liquid flow, and then compared with the experimental results given in a previous work. The variational calculation of the governing equations shows: (1) The double disc- and triple disc-type instabilities observed in the water experiments result from an ellipsoidal initial shape. (2) The jet formation occurs in the downstream direction, as observed in the glycerin experiments. (3) The instability is more easily excited in a prolate bubble. (4) The larger the size of a prolate bubble, and the higher the flow velocity, the more that induced deformation becomes flat-topped in the case of glycerin.

  13. A Robust and Low-Complexity Gas Recognition Technique for On-Chip Tin-Oxide Gas Sensor Array

    Directory of Open Access Journals (Sweden)

    Farid Flitti

    2008-01-01

    Full Text Available Gas recognition is a new emerging research area with many civil, military, and industrial applications. The success of any gas recognition system depends on its computational complexity and its robustness. In this work, we propose a new low-complexity recognition method which is tested and successfully validated for tin-oxide gas sensor array chip. The recognition system is based on a vector angle similarity measure between the query gas and the representatives of the different gas classes. The latter are obtained using a clustering algorithm based on the same measure within the training data set. Experimented results on our in-house gas sensors array show more than 98% of correct recognition. The robustness of the proposed method is tested by recognizing gas measurements with simulated drift. Less than 1% of performance degradation is noted at the worst case scenario which represents a significant improvement when compared to the current state-of-the-art.

  14. The Precise Mechanisms of a High-Speed Ultrasound Gas Sensor and Detecting Human-Specific Lung Gas Exchange

    Directory of Open Access Journals (Sweden)

    Hideki Toda

    2012-12-01

    Full Text Available In this paper, we propose and develop a new real-time human respiration process analysis method using a high-time-sampling gas concentration sensor based on ultrasound. A unique point about our proposed gas concentration sensor is its 1 kHz gas concentration sampling speed. This figure could not have been attained by previously proposed gas concentration measurement methods such as InfraRed, semiconductor gas sensors, or GC-MS, because the gas analysis speeds were a maximum of a few hundred milliseconds. First, we describe the proposed new ultrasound sound speed measurement method and the signal processing, and present the measurement circuit diagram. Next, we analyse the human respiration gas variation patterns of five healthy subjects using a newly developed gas-mask-type respiration sensor. This reveals that the rapid gas exchange from H2O to CO2 contains air specific to the human being. In addition, we also measured medical symptoms in subjects suffering from asthma, hyperventilation and bronchial asthma. The millisecond level high-speed analysis of the human respiration process will be useful for the next generation of healthcare, rehabilitation and sports science technology.

  15. Characterization and calibration of gas sensor systems at ppb level—a versatile test gas generation system

    Science.gov (United States)

    Leidinger, Martin; Schultealbert, Caroline; Neu, Julian; Schütze, Andreas; Sauerwald, Tilman

    2018-01-01

    This article presents a test gas generation system designed to generate ppb level gas concentrations from gas cylinders. The focus is on permanent gases and volatile organic compounds (VOCs) for applications like indoor and outdoor air quality monitoring or breath analysis. In the design and the setup of the system, several issues regarding handling of trace gas concentrations have been considered, addressed and tested. This concerns not only the active fluidic components (flow controllers, valves), which have been chosen specifically for the task, but also the design of the fluidic tubing regarding dead volumes and delay times, which have been simulated for the chosen setup. Different tubing materials have been tested for their adsorption/desorption characteristics regarding naphthalene, a highly relevant gas for indoor air quality monitoring, which has generated high gas exchange times in a previous gas mixing system due to long time adsorption/desorption effects. Residual gas contaminations of the system and the selected carrier air supply have been detected and quantified using both an analytical method (GC-MS analysis according to ISO 16000-6) and a metal oxide semiconductor gas sensor, which detected a maximum contamination equivalent to 28 ppb of carbon monoxide. A measurement strategy for suppressing even this contamination has been devised, which allows the system to be used for gas sensor and gas sensor system characterization and calibration in the low ppb concentration range.

  16. Semiconductor Gas Sensors Based on Pd/SnO2 Nanomaterials for Methane Detection in Air

    Science.gov (United States)

    Fedorenko, George; Oleksenko, Ludmila; Maksymovych, Nelly; Skolyar, Galina; Ripko, Oleksandr

    2017-05-01

    Semiconductor sensors based on nanosized Pd-containing tin dioxide have been obtained by a sol-gel technique. Semiconductor gas-sensitive materials were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) methods. Influence of Pd additives on sensitivity of the sensors to methane has been studied. Temperature dependences of electrical resistance in air and sensor response to methane on palladium content for the sensors based on nanosized materials Pd/SnO2 have been investigated.

  17. Evanescent-wave Infrared Optical Fiber Gas Sensor

    Science.gov (United States)

    Wang, Yiding; Wang, Di; Zhong, Hong-Jie; Zhang, Zhiguo

    2000-03-01

    We propose the treatment of amblyopia using yellow-green laser diodes.There are amblyopia children in excess of fifty million in the world.Because the causative agent of amblyopia hasn't been well understood,only roughly considered to be concerned with visual sense cell,optic nerve network and function of nerve center,no appropriate treatment is found up to date.The vision of person is determined by the center hollow region of retina,where there are three kinds of cone cell.The corresponding peak wavelength in absorption spectrum locates 447nm(blue light),532nm (green light)and 565nm(yellow light), respectively.When stimulated by white light, excited degree of three kinds of cone cell are identical,or yellow-green light,to which person eye is most sensitive, will significantly takes effects.Therefore the yellow-green laser diode is suitable for treating amblyopia. The weak laser,namely laser power less than mW order of magnitude,shows curative by stimulating bion tissue.When stimulating light power density is less than 0.001W/cm,the compounding speed of nucleic acid DNA is significantly increased.The growth rate of cell,activity of enzyme,content of hemoglobin and the growth of blood vessel,are all increased.However,it's key to control the dose of light.When the dose transcend some value,a inhibition will occur.The little dose of weak laser treatment can be accumulated with a parabolic characteristics,that is the weak laser generate bion response stengthening gradually versus time.Then it will weaken gradually after the peak.When the treatment duration is longer than a certain time,a inhibition also takes place.A suggested theraphy is characterized by little dose and short treatment course. In a conclusion, the yellow-green laser diode should be used for the treatment of amblyopia.The little dose and short treatment couse are to be adopted.

  18. A Non-Intrusive Pressure Sensor by Detecting Multiple Longitudinal Waves.

    Science.gov (United States)

    Zhou, Hongliang; Lin, Weibin; Ge, Xiaocheng; Zhou, Jian

    2016-08-05

    Pressure vessels are widely used in industrial fields, and some of them are safety-critical components in the system-for example, those which contain flammable or explosive material. Therefore, the pressure of these vessels becomes one of the critical measurements for operational management. In the paper, we introduce a new approach to the design of non-intrusive pressure sensors, based on ultrasonic waves. The model of this sensor is built based upon the travel-time change of the critically refracted longitudinal wave (LCR wave) and the reflected longitudinal waves with the pressure. To evaluate the model, experiments are carried out to compare the proposed model with other existing models. The results show that the proposed model can improve the accuracy compared to models based on a single wave.

  19. Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, H. [PBI-Dansensor A/S (Denmark); Toft Soerensen, O. [Risoe National Lab., Materials Research Dept. (Denmark)

    1999-10-01

    A new type of ceramic oxygen sensors based on semiconducting oxides was developed in this project. The advantage of these sensors compared to standard ZrO{sub 2} sensors is that they do not require a reference gas and that they can be produced in small sizes. The sensor design and the techniques developed for production of these sensors are judged suitable by the participating industry for a niche production of a new generation of oxygen sensors. Materials research on new oxygen ion conducting conductors both for applications in oxygen sensors and in fuel was also performed in this project and finally a new process was developed for fabrication of ceramic tubes by dip-coating. (EHS)

  20. Interaction of Rayleigh waves with 2D dipolar exciton gas: impact of Bose–Einstein condensation

    Science.gov (United States)

    Boev, M. V.; Chaplik, A. V.; Kovalev, V. M.

    2017-12-01

    The theory of the interaction of a two-dimensional gas of indirect dipolar excitons with Rayleigh surface elastic waves has been developed. The absorption and renormalization of the phase velocity of a surface wave, as well as the drag of excitons by the surface acoustic wave and the generation of bulk acoustic waves by a two dimensional gas of dipolar excitons irradiated by external electromagnetic radiation, have been considered. These effects have been studied both in a normal phase at high temperatures and in a condensed phase of the exciton gas. The calculations have been performed in the ballistic and diffusion limits for both phases.

  1. Nanostructured ZnO films for potential use in LPG gas sensors

    Science.gov (United States)

    Latyshev, V. M.; Berestok, T. O.; Opanasyuk, A. S.; Kornyushchenko, A. S.; Perekrestov, V. I.

    2017-05-01

    The aim of the work was to obtain ZnO nanostructures with heightened surface area and to study relationship between formation method and gas sensor properties towards propane-butane mixture (LPG). In order to synthesize ZnO nanostructures chemical and physical formation methods have been utilized. The first one was chemical bath deposition technology and the second one magnetron sputtering of Zn followed by oxidation. Optimal method and technological parameters corresponding to formation of material with the highest sensor response have been determined experimentally. Dynamical gas sensor response at different temperature values and dependencies of the sensor sensitivity on the temperature at different LPG concentrations in air have been investigated. It has been found, that sensor response depends on the sample morphology and has the highest value for the structure consisting of thin nanowires. The factors that lead to the decrease in the gas sensor operating temperature have been determined.

  2. Low Power Greenhouse Gas Sensors for Unmanned Aerial Vehicles

    Directory of Open Access Journals (Sweden)

    David J. Lary

    2012-05-01

    Full Text Available We demonstrate compact, low power, lightweight laser-based sensors for measuring trace gas species in the atmosphere designed specifically for electronic unmanned aerial vehicle (UAV platforms. The sensors utilize non-intrusive optical sensing techniques to measure atmospheric greenhouse gas concentrations with unprecedented vertical and horizontal resolution (~1 m within the planetary boundary layer. The sensors are developed to measure greenhouse gas species including carbon dioxide, water vapor and methane in the atmosphere. Key innovations are the coupling of very low power vertical cavity surface emitting lasers (VCSELs to low power drive electronics and sensitive multi-harmonic wavelength modulation spectroscopic techniques. The overall mass of each sensor is between 1–2 kg including batteries and each one consumes less than 2 W of electrical power. In the initial field testing, the sensors flew successfully onboard a T-Rex Align 700E robotic helicopter and showed a precision of 1% or less for all three trace gas species. The sensors are battery operated and capable of fully automated operation for long periods of time in diverse sensing environments. Laser-based trace gas sensors for UAVs allow for high spatial mapping of local greenhouse gas concentrations in the atmospheric boundary layer where land/atmosphere fluxes occur. The high-precision sensors, coupled to the ease-of-deployment and cost effectiveness of UAVs, provide unprecedented measurement capabilities that are not possible with existing satellite-based and suborbital aircraft platforms.

  3. Solid State Gas Sensor Research in Germany – a Status Report

    Directory of Open Access Journals (Sweden)

    Udo Weimar

    2009-06-01

    Full Text Available This status report overviews activities of the German gas sensor research community. It highlights recent progress in the field of potentiometric, amperometric, conductometric, impedimetric, and field effect-based gas sensors. It is shown that besides step-by-step improvements of conventional principles, e.g. by the application of novel materials, novel principles turned out to enable new markets. In the field of mixed potential gas sensors, novel materials allow for selective detection of combustion exhaust components. The same goal can be reached by using zeolites for impedimetric gas sensors. Operando spectroscopy is a powerful tool to learn about the mechanisms in n-type and in p-type conductometric sensors and to design knowledge-based improved sensor devices. Novel deposition methods are applied to gain direct access to the material morphology as well as to obtain dense thick metal oxide films without high temperature steps. Since conductometric and impedimetric sensors have the disadvantage that a current has to pass the gas sensitive film, film morphology, electrode materials, and geometrical issues affect the sensor signal. Therefore, one tries to measure directly the Fermi level position either by measuring the gas-dependent Seebeck coefficient at high temperatures or at room temperature by applying a modified miniaturized Kelvin probe method, where surface adsorption-based work function changes drive the drain-source current of a field effect transistor.

  4. Construction of MoS2/Si nanowire array heterojunction for ultrahigh-sensitivity gas sensor

    Science.gov (United States)

    Wu, Di; Lou, Zhenhua; Wang, Yuange; Xu, Tingting; Shi, Zhifeng; Xu, Junmin; Tian, Yongtao; Li, Xinjian

    2017-10-01

    Few-layer MoS2 thin films were synthesized by a two-step thermal decomposition process. In addition, MoS2/Si nanowire array (SiNWA) heterojunctions exhibiting excellent gas sensing properties were constructed and investigated. Further analysis reveals that such MoS2/SiNWA heterojunction devices are highly sensitive to nitric oxide (NO) gas under reverse voltages at room temperature (RT). The gas sensor demonstrated a minimum detection limit of 10 ppb, which represents the lowest value obtained for MoS2-based sensors, as well as an ultrahigh response of 3518% (50 ppm NO, ∼50% RH), with good repeatability and selectivity of the MoS2/SiNWA heterojunction. The sensing mechanisms were also discussed. The performance of the MoS2/SiNWA heterojunction gas sensors is superior to previous results, revealing that they have great potential in applications relating to highly sensitive gas sensors.

  5. Catalysis-Based Cataluminescent and Conductometric Gas Sensors: Sensing Nanomaterials, Mechanism, Applications and Perspectives

    Directory of Open Access Journals (Sweden)

    Jinyun Liu

    2016-12-01

    Full Text Available Gas environment detection has become more urgent and significant, for both industrial manufacturing and environment monitoring. Gas sensors based on a catalytically-sensing mechanism are one of the most important types of devices for gas detection, and have been of great interest during the past decades. However, even though many efforts have contributed to this area, some great challenges still remain, such as the development of sensitively and selectively sensing catalysts. In this review, two representative catalysis-based gas sensors, cataluminescent and conductometric sensors, the basis of optical and electric signal acquisition, respectively, are summarized comprehensively. The current challenges have been presented. Recent research progress on the working mechanism, sensing nanomaterials, and applications reported by our group and some other researchers have been discussed systematically. The future trends and prospects of the catalysis-based gas sensors have also been presented.

  6. Design and Implementation of an Electronic Front-End Based on Square Wave Excitation for Ultrasonic Torsional Guided Wave Viscosity Sensor.

    Science.gov (United States)

    Rabani, Amir

    2016-10-12

    The market for process instruments generally requires low cost devices that are robust, small in size, portable, and usable in-plant. Ultrasonic torsional guided wave sensors have received much attention by researchers for measurement of viscosity and/or density of fluids in recent years. The supporting electronic systems for these sensors providing many different settings of sine-wave signals are bulky and expensive. In contrast, a system based on bursts of square waves instead of sine waves would have a considerable advantage in that respect and could be built using simple integrated circuits at a cost that is orders of magnitude lower than for a windowed sine wave device. This paper explores the possibility of using square wave bursts as the driving signal source for the ultrasonic torsional guided wave viscosity sensor. A simple design of a compact and fully automatic analogue square wave front-end for the sensor is also proposed. The successful operation of the system is demonstrated by using the sensor for measuring the viscosity in a representative fluid. This work provides the basis for design and manufacture of low cost compact standalone ultrasonic guided wave sensors and enlightens the possibility of using coded excitation techniques utilising square wave sequences in such applications.

  7. CW DFB RT diode laser-based sensor for trace-gas detection of ethane using a novel compact multipass gas absorption cell

    Science.gov (United States)

    Krzempek, Karol; Jahjah, Mohammad; Lewicki, Rafał; Stefański, Przemysław; So, Stephen; Thomazy, David; Tittel, Frank K.

    2013-09-01

    The development of a continuous wave, thermoelectrically cooled (TEC), distributed feedback diode laser-based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy as the detection technique. TDLAS was performed using an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm and optimized for the 2.5-4 μm range TEC mercury-cadmium-telluride detector. For an interference-free C2H6 absorption line located at 2,976.8 cm-1, a 1 σ minimum detection limit of 740 pptv with a 1 s lock-in amplifier time constant was achieved.

  8. Metal-oxide-semiconductor based gas sensors: screening, preparation, and integration.

    Science.gov (United States)

    Zhang, Jian; Qin, Ziyu; Zeng, Dawen; Xie, Changsheng

    2017-03-01

    Metal-oxide-semiconductor (MOS) based gas sensors have been considered a promising candidate for gas detection over the past few years. However, the sensing properties of MOS-based gas sensors also need to be further enhanced to satisfy the higher requirements for specific applications, such as medical diagnosis based on human breath, gas detection in harsh environments, etc. In these fields, excellent selectivity, low power consumption, a fast response/recovery rate, low humidity dependence and a low limit of detection concentration should be fulfilled simultaneously, which pose great challenges to the MOS-based gas sensors. Recently, in order to improve the sensing performances of MOS-based gas sensors, more and more researchers have carried out extensive research from theory to practice. For a similar purpose, on the basis of the whole fabrication process of gas sensors, this review gives a presentation of the important role of screening and the recent developments in high throughput screening. Subsequently, together with the sensing mechanism, the factors influencing the sensing properties of MOSs involved in material preparation processes were also discussed in detail. It was concluded that the sensing properties of MOSs not only depend on the morphological structure (particle size, morphology, pore size, etc.), but also rely on the defect structure and heterointerface structure (grain boundaries, heterointerfaces, defect concentrations, etc.). Therefore, the material-sensor integration was also introduced to maintain the structural stability in the sensor fabrication process, ensuring the sensing stability of MOS-based gas sensors. Finally, the perspectives of the MOS-based gas sensors in the aspects of fundamental research and the improvements in the sensing properties are pointed out.

  9. SnO2 Nanostructure as Pollutant Gas Sensors: Synthesis, Sensing Performances, and Mechanism

    Directory of Open Access Journals (Sweden)

    Brian Yuliarto

    2015-01-01

    Full Text Available A significant amount of pollutants is produced from factories and motor vehicles in the form of gas. Their negative impact on the environment is well known; therefore detection with effective gas sensors is important as part of pollution prevention efforts. Gas sensors use a metal oxide semiconductor, specifically SnO2 nanostructures. This semiconductor is interesting and worthy of further investigation because of its many uses, for example, as lithium battery electrode, energy storage, catalyst, and transistor, and has potential as a gas sensor. In addition, there has to be a discussion of the use of SnO2 as a pollutant gas sensor especially for waste products such as CO, CO2, SO2, and NOx. In this paper, the development of the fabrication of SnO2 nanostructures synthesis will be described as it relates to the performances as pollutant gas sensors. In addition, the functionalization of SnO2 as a gas sensor is extensively discussed with respect to the theory of gas adsorption, the surface features of SnO2, the band gap theory, and electron transfer.

  10. Membrane-Based Characterization of a Gas Component — A Transient Sensor Theory

    Science.gov (United States)

    Lazik, Detlef

    2014-01-01

    Based on a multi-gas solution-diffusion problem for a dense symmetrical membrane this paper presents a transient theory of a planar, membrane-based sensor cell for measuring gas from both initial conditions: dynamic and thermodynamic equilibrium. Using this theory, the ranges for which previously developed, simpler approaches are valid will be discussed; these approaches are of vital interest for membrane-based gas sensor applications. Finally, a new theoretical approach is introduced to identify varying gas components by arranging sensor cell pairs resulting in a concentration independent gas-specific critical time. Literature data for the N2, O2, Ar, CH4, CO2, H2 and C4H10 diffusion coefficients and solubilities for a polydimethylsiloxane membrane were used to simulate gas specific sensor responses. The results demonstrate the influence of (i) the operational mode; (ii) sensor geometry and (iii) gas matrices (air, Ar) on that critical time. Based on the developed theory the case-specific suitable membrane materials can be determined and both operation and design options for these sensors can be optimized for individual applications. The results of mixing experiments for different gases (O2, CO2) in a gas matrix of air confirmed the theoretical predictions. PMID:24608004

  11. Membrane-based characterization of a gas component--a transient sensor theory.

    Science.gov (United States)

    Lazik, Detlef

    2014-03-07

    Based on a multi-gas solution-diffusion problem for a dense symmetrical membrane this paper presents a transient theory of a planar, membrane-based sensor cell for measuring gas from both initial conditions: dynamic and thermodynamic equilibrium. Using this theory, the ranges for which previously developed, simpler approaches are valid will be discussed; these approaches are of vital interest for membrane-based gas sensor applications. Finally, a new theoretical approach is introduced to identify varying gas components by arranging sensor cell pairs resulting in a concentration independent gas-specific critical time. Literature data for the N2, O2, Ar, CH4, CO2, H2 and C4H10 diffusion coefficients and solubilities for a polydimethylsiloxane membrane were used to simulate gas specific sensor responses. The results demonstrate the influence of (i) the operational mode; (ii) sensor geometry and (iii) gas matrices (air, Ar) on that critical time. Based on the developed theory the case-specific suitable membrane materials can be determined and both operation and design options for these sensors can be optimized for individual applications. The results of mixing experiments for different gases (O2, CO2) in a gas matrix of air confirmed the theoretical predictions.

  12. Membrane-Based Characterization of a Gas Component — A Transient Sensor Theory

    Directory of Open Access Journals (Sweden)

    Detlef Lazik

    2014-03-01

    Full Text Available Based on a multi-gas solution-diffusion problem for a dense symmetrical membrane this paper presents a transient theory of a planar, membrane-based sensor cell for measuring gas from both initial conditions: dynamic and thermodynamic equilibrium. Using this theory, the ranges for which previously developed, simpler approaches are valid will be discussed; these approaches are of vital interest for membrane-based gas sensor applications. Finally, a new theoretical approach is introduced to identify varying gas components by arranging sensor cell pairs resulting in a concentration independent gas-specific critical time. Literature data for the N2, O2, Ar, CH4, CO2, H2 and C4H10 diffusion coefficients and solubilities for a polydimethylsiloxane membrane were used to simulate gas specific sensor responses. The results demonstrate the influence of (i the operational mode; (ii sensor geometry and (iii gas matrices (air, Ar on that critical time. Based on the developed theory the case-specific suitable membrane materials can be determined and both operation and design options for these sensors can be optimized for individual applications. The results of mixing experiments for different gases (O2, CO2 in a gas matrix of air confirmed the theoretical predictions.

  13. Reduced graphene oxide for room-temperature gas sensors

    Energy Technology Data Exchange (ETDEWEB)

    Lu Ganhua; Chen Junhong [Department of Mechanical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 (United States); Ocola, Leonidas E, E-mail: jhchen@uwm.ed [Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2009-11-04

    We demonstrated high-performance gas sensors based on graphene oxide (GO) sheets partially reduced via low-temperature thermal treatments. Hydrophilic graphene oxide sheets uniformly suspended in water were first dispersed onto gold interdigitated electrodes. The partial reduction of the GO sheets was then achieved through low-temperature, multi-step annealing (100, 200, and 300 {sup 0}C) or one-step heating (200 {sup 0}C) of the device in argon flow at atmospheric pressure. The electrical conductance of GO was measured after each heating cycle to interpret the level of reduction. The thermally-reduced GO showed p-type semiconducting behavior in ambient conditions and was responsive to low-concentration NO{sub 2} and NH{sub 3} gases diluted in air at room temperature. The sensitivity can be attributed mainly to the electron transfer between the reduced GO and adsorbed gaseous molecules (NO{sub 2}/NH{sub 3}). Additionally, the contact between GO and the Au electrode is likely to contribute to the overall sensing response because of the adsorbates-induced Schottky barrier variation. A simplified model is used to explain the experimental observations.

  14. Reduced graphene oxide for room-temperature gas sensors.

    Science.gov (United States)

    Lu, Ganhua; Ocola, Leonidas E; Chen, Junhong

    2009-11-04

    We demonstrated high-performance gas sensors based on graphene oxide (GO) sheets partially reduced via low-temperature thermal treatments. Hydrophilic graphene oxide sheets uniformly suspended in water were first dispersed onto gold interdigitated electrodes. The partial reduction of the GO sheets was then achieved through low-temperature, multi-step annealing (100, 200, and 300 degrees C) or one-step heating (200 degrees C) of the device in argon flow at atmospheric pressure. The electrical conductance of GO was measured after each heating cycle to interpret the level of reduction. The thermally-reduced GO showed p-type semiconducting behavior in ambient conditions and was responsive to low-concentration NO2 and NH3 gases diluted in air at room temperature. The sensitivity can be attributed mainly to the electron transfer between the reduced GO and adsorbed gaseous molecules (NO2/NH3). Additionally, the contact between GO and the Au electrode is likely to contribute to the overall sensing response because of the adsorbates-induced Schottky barrier variation. A simplified model is used to explain the experimental observations.

  15. Reduced graphene oxide for room-temperature gas sensors

    Science.gov (United States)

    Lu, Ganhua; Ocola, Leonidas E.; Chen, Junhong

    2009-11-01

    We demonstrated high-performance gas sensors based on graphene oxide (GO) sheets partially reduced via low-temperature thermal treatments. Hydrophilic graphene oxide sheets uniformly suspended in water were first dispersed onto gold interdigitated electrodes. The partial reduction of the GO sheets was then achieved through low-temperature, multi-step annealing (100, 200, and 300 °C) or one-step heating (200 °C) of the device in argon flow at atmospheric pressure. The electrical conductance of GO was measured after each heating cycle to interpret the level of reduction. The thermally-reduced GO showed p-type semiconducting behavior in ambient conditions and was responsive to low-concentration NO2 and NH3 gases diluted in air at room temperature. The sensitivity can be attributed mainly to the electron transfer between the reduced GO and adsorbed gaseous molecules (NO2/NH3). Additionally, the contact between GO and the Au electrode is likely to contribute to the overall sensing response because of the adsorbates-induced Schottky barrier variation. A simplified model is used to explain the experimental observations.

  16. Facile Fabrication of Multi-hierarchical Porous Polyaniline Composite as Pressure Sensor and Gas Sensor with Adjustable Sensitivity

    Science.gov (United States)

    He, Xiao-Xiao; Li, Jin-Tao; Jia, Xian-Sheng; Tong, Lu; Wang, Xiao-Xiong; Zhang, Jun; Zheng, Jie; Ning, Xin; Long, Yun-Ze

    2017-08-01

    A multi-hierarchical porous polyaniline (PANI) composite which could be used in good performance pressure sensor and adjustable sensitivity gas sensor has been fabricated by a facile in situ polymerization. Commercial grade sponge was utilized as a template scaffold to deposit PANI via in situ polymerization. With abundant interconnected pores throughout the whole structure, the sponge provided sufficient surface for the growth of PANI nanobranches. The flexible porous structure helped the composite to show high performance in pressure detection with fast response and favorable recoverability and gas detection with adjustable sensitivity. The sensing mechanism of the PANI/sponge-based flexible sensor has also been discussed. The results indicate that this work provides a feasible approach to fabricate efficient sensors with advantages of low cost, facile preparation, and easy signal collection.

  17. Gas adsorption on monolayer blue phosphorus: implications for environmental stability and gas sensors

    Science.gov (United States)

    Liu, Nanshu; Zhou, Si

    2017-04-01

    Monolayer blue phosphorus has recently been synthesized by molecular beam epitaxial growth on Au(111) substrate. It is intriguing to compare this new 2D phase of phosphorus with phosphorene as to both fundamental properties and application prospects. Here, first-principles calculations are carried out to explore the adsorption behaviors of environmental gas molecules on monolayer blue phosphorus, including O2, NO, SO2, NH3, H2O, NO2, CO2, H2S, CO, and N2, and address their effects on the electronic properties of the material. Our calculations show that O2 is prone to dissociate and tends to chemisorb on the blue phosphorus sheet, phenomena which has also been observed in phosphorene. The other gas molecules can stably physisorb on monolayer blue phosphorus, showing different interaction strengths with the monolayer. These molecules induce distinct modifications to the band gap, carrier effective mass, and work function, which also depends on the molecular coverage. The responses of the electronic properties are subject to the charge transfer as well as alignment of the frontier molecular orbital levels of the gaseous molecules and band edges of the parent sheet. These results suggest that monolayer blue phosphorus is a promising candidate for novel gas sensors.

  18. Ultra-Low-Power MEMS Selective Gas Sensors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — KWJ offers this proposal for a very low power but very practical "nano-watt" MEMS sensor platform for NASA requirements. The proposed nano-sensor platform is ultra...

  19. Plasmonic nanocomposite thin film enabled fiber optic sensors for simultaneous gas and temperature sensing at extreme temperatures.

    Science.gov (United States)

    Ohodnicki, Paul R; Buric, Michael P; Brown, Thomas D; Matranga, Christopher; Wang, Congjun; Baltrus, John; Andio, Mark

    2013-10-07

    Embedded sensors capable of operation in extreme environments including high temperatures, high pressures, and highly reducing, oxidizing and/or corrosive environments can make a significant impact on enhanced efficiencies and reduced greenhouse gas emissions of current and future fossil-based power generation systems. Relevant technologies can also be leveraged in a wide range of other applications with similar needs including nuclear power generation, industrial process monitoring and control, and aviation/aerospace. Here we describe a novel approach to embedded sensing under extreme temperature conditions by integration of Au-nanoparticle based plasmonic nanocomposite thin films with optical fibers in an evanescent wave absorption spectroscopy configuration. Such sensors can potentially enable simultaneous temperature and gas sensing at temperatures approaching 900-1000 °C in a manner compatible with embedded and distributed sensing approaches. The approach is demonstrated using the Au/SiO2 system deposited on silica-based optical fibers. Stability of optical fibers under relevant high temperature conditions and interactions with changing ambient gas atmospheres is an area requiring additional investigation and development but the simplicity of the sensor design makes it potentially cost-effective and may offer a potential for widespread deployment.

  20. Sensitivity Distribution Properties of a Phase-Shifted Fiber Bragg Grating Sensor to Ultrasonic Waves

    Directory of Open Access Journals (Sweden)

    Qi Wu

    2014-01-01

    Full Text Available In this research, the sensitivity distribution properties of a phase-shifted fiber Bragg grating (PS-FBG to ultrasonic waves were investigated employing the surface attachment method. A careful consideration was taken and examined by experimental results to explain that the distances and angles between the sensor and ultrasonic source influence not only the amplitudes, but also the initial phases, waveforms, and spectra of detected signals. Furthermore, factors, including the attachment method and the material’s geometric dimensions, were also discussed. Although these results were obtained based on PS-FBG, they are also applicable to a normal FBG sensor or even an optical fiber sensor, due to the identical physical changes induced by ultrasonic waves in all three. Thus, these results are useful for applications of optical fiber sensors in non-destructive testing and structural health monitoring.

  1. Sensitivity distribution properties of a phase-shifted fiber bragg grating sensor to ultrasonic waves.

    Science.gov (United States)

    Wu, Qi; Okabe, Yoji; Saito, Kazuya; Yu, Fengming

    2014-01-09

    In this research, the sensitivity distribution properties of a phase-shifted fiber Bragg grating (PS-FBG) to ultrasonic waves were investigated employing the surface attachment method. A careful consideration was taken and examined by experimental results to explain that the distances and angles between the sensor and ultrasonic source influence not only the amplitudes, but also the initial phases, waveforms, and spectra of detected signals. Furthermore, factors, including the attachment method and the material's geometric dimensions, were also discussed. Although these results were obtained based on PS-FBG, they are also applicable to a normal FBG sensor or even an optical fiber sensor, due to the identical physical changes induced by ultrasonic waves in all three. Thus, these results are useful for applications of optical fiber sensors in non-destructive testing and structural health monitoring.

  2. Advanced Gas Sensors Using SERS-Activated Waveguides

    Science.gov (United States)

    Lascola, Robert; McWhorter, Scott; Murph, Simona Hunyadi

    2010-08-01

    non-specific interactions between the surface coating and additional nanoparticles suspended in solution to which the analyte had been coupled. Clearly, for a gas sensor, such a scheme is not feasible, and in any event the reliance on the random configuration of the nanoparticles and the analyte is not expected to lead to efficient enhancement. Here, we report the creation of capillary coatings of self-assembled, aggregated high aspect ratio metallic nanoparticles (e.g. rod, wires) with a solution-phase technique. Self-assembly offers the possibility for a high density of SERS hot spots, which are often observed at the junction of adjacent particles. Shaped nanoparticles also enhance self-assembled deposition, and allow further control of the optical properties of the coating through manipulation of the morphology. SERS enhancements for gases are reported relative to mirrored capillaries and free-space measurements.

  3. On-chip growth of semiconductor metal oxide nanowires for gas sensors: A review

    Directory of Open Access Journals (Sweden)

    Chu Manh Hung

    2017-09-01

    Full Text Available Semiconductor metal oxide nanowires (SMO-NWs show great potential for novel gas sensor applications because of their distinct properties, such as a high surface area to volume aspect ratio, high crystallinity and perfect pathway for electron transfer (length of NW. SMO-NW sensors can be configured as resistors or field-effect transistors for gas detection and different configurations, such as a single NW, multiple NWs, and networked NW films, have been established. Surface-functionalizing NWs with catalyst elements and self-heating NWs provide additional advantages for highly selective and low-power consumption gas sensors. However, an appropriate design of SMO-NWs is of practical importance in enhancing the gas-sensing performance of SMO-NW sensors. The on-chip growth of SMO-NWs possesses many advantages which can thus be effectively used for the large-scale fabrication of SMO-NW sensors with improved gas response and stability. This review aims to provide up-to-date information on the on-chip fabrication of SnO2, ZnO, WO3, CuO, and other SMO-NW sensors. It also discusses a variety of promising approaches that help advance the on-chip fabrication of SMO-NW-based gas sensors and other NW-based devices.

  4. A Finite Element Model of a MEMS-based Surface Acoustic Wave Hydrogen Sensor

    Directory of Open Access Journals (Sweden)

    Walied A. Moussa

    2010-02-01

    Full Text Available Hydrogen plays a significant role in various industrial applications, but careful handling and continuous monitoring are crucial since it is explosive when mixed with air. Surface Acoustic Wave (SAW sensors provide desirable characteristics for hydrogen detection due to their small size, low fabrication cost, ease of integration and high sensitivity. In this paper a finite element model of a Surface Acoustic Wave sensor is developed using ANSYS12© and tested for hydrogen detection. The sensor consists of a YZ-lithium niobate substrate with interdigital electrodes (IDT patterned on the surface. A thin palladium (Pd film is added on the surface of the sensor due to its high affinity for hydrogen. With increased hydrogen absorption the palladium hydride structure undergoes a phase change due to the formation of the β-phase, which deteriorates the crystal structure. Therefore with increasing hydrogen concentration the stiffness and the density are significantly reduced. The values of the modulus of elasticity and the density at different hydrogen concentrations in palladium are utilized in the finite element model to determine the corresponding SAW sensor response. Results indicate that with increasing the hydrogen concentration the wave velocity decreases and the attenuation of the wave is reduced.

  5. Detection of coffee flavour ageing by solid-phase microextraction/surface acoustic wave sensor array technique (SPME/SAW).

    Science.gov (United States)

    Barié, Nicole; Bücking, Mark; Stahl, Ullrich; Rapp, Michael

    2015-06-01

    The use of polymer coated surface acoustic wave (SAW) sensor arrays is a very promising technique for highly sensitive and selective detection of volatile organic compounds (VOCs). We present new developments to achieve a low cost sensor setup with a sampling method enabling the highly reproducible detection of volatiles even in the ppb range. Since the VOCs of coffee are well known by gas chromatography (GC) research studies, the new sensor array was tested for an easy assessable objective: coffee ageing during storage. As reference method these changes were traced with a standard GC/FID set-up, accompanied by sensory panellists. The evaluation of GC data showed a non-linear characteristic for single compound concentrations as well as for total peak area values, disabling prediction of the coffee age. In contrast, the new SAW sensor array demonstrates a linear dependency, i.e. being capable to show a dependency between volatile concentration and storage time. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Sensor Selection for Aircraft Engine Performance Estimation and Gas Path Fault Diagnostics

    Science.gov (United States)

    Simon, Donald L.; Rinehart, Aidan W.

    2016-01-01

    This paper presents analytical techniques for aiding system designers in making aircraft engine health management sensor selection decisions. The presented techniques, which are based on linear estimation and probability theory, are tailored for gas turbine engine performance estimation and gas path fault diagnostics applications. They enable quantification of the performance estimation and diagnostic accuracy offered by different candidate sensor suites. For performance estimation, sensor selection metrics are presented for two types of estimators including a Kalman filter and a maximum a posteriori estimator. For each type of performance estimator, sensor selection is based on minimizing the theoretical sum of squared estimation errors in health parameters representing performance deterioration in the major rotating modules of the engine. For gas path fault diagnostics, the sensor selection metric is set up to maximize correct classification rate for a diagnostic strategy that performs fault classification by identifying the fault type that most closely matches the observed measurement signature in a weighted least squares sense. Results from the application of the sensor selection metrics to a linear engine model are presented and discussed. Given a baseline sensor suite and a candidate list of optional sensors, an exhaustive search is performed to determine the optimal sensor suites for performance estimation and fault diagnostics. For any given sensor suite, Monte Carlo simulation results are found to exhibit good agreement with theoretical predictions of estimation and diagnostic accuracies.

  7. High-Density Fiber Optical Sensor and Instrumentation for Gas Turbine Operation Condition Monitoring

    Directory of Open Access Journals (Sweden)

    Hua Xia

    2013-01-01

    Full Text Available Gas turbine operation control is normally based on thermocouple-measured exhaust temperatures. Due to radiation shielding and bulky package, it is difficult to provide high spatial resolution for measuring can-to-can combustion temperature profile at the exhaust duct. This paper has demonstrated that wavelength-division-multiplexing-based fiber Bragg grating sensors could provide high spatial resolution steady and dynamic temperature measurements. A robust sensor package can be designed with either circumferential sensing cable or radial sensing rake for quasi-distributing multiple fiber sensors in the gas turbine environment. The field validations have demonstrated that quasi-distributed fiber sensors have not only demonstrated its temperature measurement accuracy compared to existing thermocouple sensors but also shown its unique dynamic response amplitude and power spectra that could be utilized for gas turbine transient operation condition monitoring and diagnostics.

  8. Determination of gas composition in a biogas plant using a Raman-based sensor system

    Science.gov (United States)

    Eichmann, S. C.; Kiefer, J.; Benz, J.; Kempf, T.; Leipertz, A.; Seeger, T.

    2014-07-01

    We propose a gas sensor, based on spontaneous Raman scattering, for the compositional analysis of typical biogas mixtures and present a description of the sensor, as well as of the calibration procedure, which allows the quantification of condensable gases. Moreover, we carry out a comprehensive characterization of the system, in order to determine the measurement uncertainty, as well as influences of temperature and pressure fluctuation. Finally, the sensor is applied at different locations inside a plant in which biogas is produced from renewable raw materials. The composition is monitored after fermenting, after purification and after the final conditioning, where natural gas is added. The Raman sensor is able to detect all the relevant gas components, i.e. CH4, CO2, N2 and H2O, and report their individual concentrations over time. The results were compared to reference data from a conventional gas analyzer and good agreement was obtained.

  9. Inflammable Gas Mixture Detection with a Single Catalytic Sensor Based on the Electric Field Effect

    Science.gov (United States)

    Tong, Ziyuan; Tong, Min-Ming; Meng, Wen; Li, Meng

    2014-01-01

    This paper introduces a new way to analyze mixtures of inflammable gases with a single catalytic sensor. The analysis technology was based on a new finding that an electric field on the catalytic sensor can change the output sensitivity of the sensor. The analysis of mixed inflammable gases results from processing the output signals obtained by adjusting the electric field parameter of the catalytic sensor. For the signal process, we designed a group of equations based on the heat balance of catalytic sensor expressing the relationship between the output signals and the concentration of gases. With these equations and the outputs of different electric fields, the gas concentration in a mixture could be calculated. In experiments, a mixture of methane, butane and ethane was analyzed by this new method, and the results showed that the concentration of each gas in the mixture could be detected with a single catalytic sensor, and the maximum relative error was less than 5%. PMID:24717635

  10. Surface acoustic wave sensors with Graphene/PANI nanocomposites for nitric oxide detection

    Science.gov (United States)

    Wang, Beibei; Zheng, Lei; Zhou, Lingling

    2017-12-01

    Surface acoustic wave sensors with grapheme/PANI nanocomposite sensitive films for detecting nitric oxide (NO) were fabricated and experimentally studied. Morphological characterization and functionalization of the sensing material were explored using SEM and FTIR, respectively. The study of sensor response compared film sensitivity, response time, reversibility, and limit of detection for nanocomposite films, pure grapheme and pure PANI to the detection of NO. The response and recovery times were 40s and 20s when detecting 4ppm NO, respectively. The frequency response was discovered to be linear in the NO concentration range 1–50 ppm. The nanocomposite sensors had improved sensitivities compared to the polymer devices, and better response times.

  11. Selective Sensing of Gas Mixture via a Temperature Modulation Approach: New Strategy for Potentiometric Gas Sensor Obtaining Satisfactory Discriminating Features.

    Science.gov (United States)

    Li, Fu-An; Jin, Han; Wang, Jinxia; Zou, Jie; Jian, Jiawen

    2017-03-12

    A new strategy to discriminate four types of hazardous gases is proposed in this research. Through modulating the operating temperature and the processing response signal with a pattern recognition algorithm, a gas sensor consisting of a single sensing electrode, i.e., ZnO/In₂O₃ composite, is designed to differentiate NO₂, NH₃, C₃H₆, CO within the level of 50-400 ppm. Results indicate that with adding 15 wt.% ZnO to In₂O₃, the sensor fabricated at 900 °C shows optimal sensing characteristics in detecting all the studied gases. Moreover, with the aid of the principle component analysis (PCA) algorithm, the sensor operating in the temperature modulation mode demonstrates acceptable discrimination features. The satisfactory discrimination features disclose the future that it is possible to differentiate gas mixture efficiently through operating a single electrode sensor at temperature modulation mode.

  12. Application of Conductive Carbon Nanotube Fibers and Composites: Gas Sensor

    Science.gov (United States)

    2013-05-01

    Resistance 5 ppm, 100 ppb (162) 2008 Penza NO2, NH3, H2S MWNT Pt, Pd Gas Resistance ə ppm (163) 2003 Li NO2, nitrotoluene SWNT -- Gas Resistance...Resistance -- (183) 2006 Parikh Toluene , acetone, hexane, water MWNT PET Gas Resistance -- (184) 2007 Consales Toluene , xylene SWNT -- Gas Optical

  13. The Effects of Two Thick Film Deposition Methods on Tin Dioxide Gas Sensor Performance

    Directory of Open Access Journals (Sweden)

    Smitesh D. Bakrania

    2009-08-01

    Full Text Available This work demonstrates the variability in performance between SnO2 thick film gas sensors prepared using two types of film deposition methods. SnO2 powders were deposited on sensor platforms with and without the use of binders. Three commonly utilized binder recipes were investigated, and a new binder-less deposition procedure was developed and characterized. The binder recipes yielded sensors with poor film uniformity and poor structural integrity, compared to the binder-less deposition method. Sensor performance at a fixed operating temperature of 330 ºC for the different film deposition methods was evaluated by exposure to 500 ppm of the target gas carbon monoxide. A consequence of the poor film structure, large variability and poor signal properties were observed with the sensors fabricated using binders. Specifically, the sensors created using the binder recipes yielded sensor responses that varied widely (e.g., S = 5 – 20, often with hysteresis in the sensor signal. Repeatable and high quality performance was observed for the sensors prepared using the binder-less dispersion-drop method with good sensor response upon exposure to 500 ppm CO (S = 4.0 at an operating temperature of 330 ºC, low standard deviation to the sensor response (±0.35 and no signal hysteresis.

  14. The effects of two thick film deposition methods on tin dioxide gas sensor performance.

    Science.gov (United States)

    Bakrania, Smitesh D; Wooldridge, Margaret S

    2009-01-01

    This work demonstrates the variability in performance between SnO(2) thick film gas sensors prepared using two types of film deposition methods. SnO(2) powders were deposited on sensor platforms with and without the use of binders. Three commonly utilized binder recipes were investigated, and a new binder-less deposition procedure was developed and characterized. The binder recipes yielded sensors with poor film uniformity and poor structural integrity, compared to the binder-less deposition method. Sensor performance at a fixed operating temperature of 330 °C for the different film deposition methods was evaluated by exposure to 500 ppm of the target gas carbon monoxide. A consequence of the poor film structure, large variability and poor signal properties were observed with the sensors fabricated using binders. Specifically, the sensors created using the binder recipes yielded sensor responses that varied widely (e.g., S = 5 - 20), often with hysteresis in the sensor signal. Repeatable and high quality performance was observed for the sensors prepared using the binder-less dispersion-drop method with good sensor response upon exposure to 500 ppm CO (S = 4.0) at an operating temperature of 330 °C, low standard deviation to the sensor response (±0.35) and no signal hysteresis.

  15. Toward high value sensing: monolayer-protected metal nanoparticles in multivariable gas and vapor sensors.

    Science.gov (United States)

    Potyrailo, Radislav A

    2017-08-29

    For detection of gases and vapors in complex backgrounds, "classic" analytical instruments are an unavoidable alternative to existing sensors. Recently a new generation of sensors, known as multivariable sensors, emerged with a fundamentally different perspective for sensing to eliminate limitations of existing sensors. In multivariable sensors, a sensing material is designed to have diverse responses to different gases and vapors and is coupled to a multivariable transducer that provides independent outputs to recognize these diverse responses. Data analytics tools provide rejection of interferences and multi-analyte quantitation. This review critically analyses advances of multivariable sensors based on ligand-functionalized metal nanoparticles also known as monolayer-protected nanoparticles (MPNs). These MPN sensing materials distinctively stand out from other sensing materials for multivariable sensors due to their diversity of gas- and vapor-response mechanisms as provided by organic and biological ligands, applicability of these sensing materials for broad classes of gas-phase compounds such as condensable vapors and non-condensable gases, and for several principles of signal transduction in multivariable sensors that result in non-resonant and resonant electrical sensors as well as material- and structure-based photonic sensors. Such features should allow MPN multivariable sensors to be an attractive high value addition to existing analytical instrumentation.

  16. Monitoring of volatiles in alcoholic fermentations on molasses via a gas membrane sensor

    Energy Technology Data Exchange (ETDEWEB)

    Groboillot, A.; Pons, M.N.; Engasser, J.M. (Centre National de la Recherche Scientifique, 54 - Nancy (France). Lab. des Sciences du Genie Chimique)

    1989-11-01

    Gas membrane sensors, connected to a gas chromatography, have been tested in fermentation on complex media of industrial interest. Selectivity, sensitivity and reliability have been assessed: The calibration of fermentation medium is recommended. The use of such a sensor is demonstrated in the study of the kinetics of batch and fed-batch alcoholic fermentations on beet molasses. The kinetics of acetaldehyde are especially pointed out in relation to ethanol, fusel alcohols and carbon dioxide production. (orig.).

  17. Gas Sensors Based on Tin Oxide Nanoparticles Synthesized from a Mini-Arc Plasma Source

    OpenAIRE

    Ganhua Lu; Huebner, Kyle L.; Ocola, Leonidas E.; Marija Gajdardziska-Josifovska; Junhong Chen

    2006-01-01

    Miniaturized gas sensors or electronic noses to rapidly detect and differentiate trace amount of chemical agents are extremely attractive. In this paper, we report on the fabrication and characterization of a functional tin oxide nanoparticle gas sensor. Tin oxide nanoparticles are first synthesized using a convenient and low-cost mini-arc plasma source. The nanoparticle size distribution is measured online using a scanning electrical mobility spectrometer (SEMS). The product nanoparticles a...

  18. On-chip growth of semiconductor metal oxide nanowires for gas sensors: A review

    OpenAIRE

    Chu Manh Hung; Dang Thi Thanh Le; Nguyen Van Hieu,

    2017-01-01

    Semiconductor metal oxide nanowires (SMO-NWs) show great potential for novel gas sensor applications because of their distinct properties, such as a high surface area to volume aspect ratio, high crystallinity and perfect pathway for electron transfer (length of NW). SMO-NW sensors can be configured as resistors or field-effect transistors for gas detection and different configurations, such as a single NW, multiple NWs, and networked NW films, have been established. Surface-functionalizing N...

  19. Conductive polymer gas sensor for quantitative detection of methanol in Brazilian sugar-cane spirit

    OpenAIRE

    Péres, Laura Oliveira [UNIFESP; Li, Rosamaria W. C.; Yamauchi, Elaine Y.; Lippi, Renata; Gruber, Jonas

    2012-01-01

    A low-cost chemiresistive gas sensor is described, made by the deposition of a thin film of a conductive polymer, poly(2-dodecanoylsulfanyl-p-phenylenevinylene), doped with dodecylbenzenesulfonic acid (10%, w/w), onto interdigitated electrodes. the sensor exhibits linear electrical conductance changes in function of the concentration of methanol present in sugar-cane spirit in the range between 0.05% and 4.0%. Since the sensor is cheap, easy to fabricate, durable, presents low power consumpti...

  20. A novel neural network-based technique for smart gas sensors operating in a dynamic environment.

    Science.gov (United States)

    Baha, Hakim; Dibi, Zohir

    2009-01-01

    Thanks to their high sensitivity and low-cost, metal oxide gas sensors (MOX) are widely used in gas detection, although they present well-known problems (lack of selectivity and environmental effects…). We present in this paper a novel neural network- based technique to remedy these problems. The idea is to create intelligent models; the first one, called corrector, can automatically linearize a sensor's response characteristics and eliminate its dependency on the environmental parameters. The corrector's responses are processed with the second intelligent model which has the role of discriminating exactly the detected gas (nature and concentration). The gas sensors used are industrial resistive kind (TGS8xx, by Figaro Engineering). The MATLAB environment is used during the design phase and optimization. The sensor models, the corrector, and the selective model were implemented and tested in the PSPICE simulator. The sensor model accurately expresses the nonlinear character of the response and the dependence on temperature and relative humidity in addition to their gas nature dependency. The corrector linearizes and compensates the sensor's responses. The method discriminates qualitatively and quantitatively between seven gases. The advantage of the method is that it uses a small representative database so we can easily implement the model in an electrical simulator. This method can be extended to other sensors.

  1. Exploitation of unique properties of zeolites in the development of gas sensors.

    Science.gov (United States)

    Zheng, Yangong; Li, Xiaogan; Dutta, Prabir K

    2012-01-01

    The unique properties of microporous zeolites, including ion-exchange properties, adsorption, molecular sieving, catalysis, conductivity have been exploited in improving the performance of gas sensors. Zeolites have been employed as physical and chemical filters to improve the sensitivity and selectivity of gas sensors. In addition, direct interaction of gas molecules with the extraframework cations in the nanoconfined space of zeolites has been explored as a basis for developing new impedance-type gas/vapor sensors. In this review, we summarize how these properties of zeolites have been used to develop new sensing paradigms. There is a considerable breadth of transduction processes that have been used for zeolite incorporated sensors, including frequency measurements, optical and the entire gamut of electrochemical measurements. It is clear from the published literature that zeolites provide a route to enhance sensor performance, and it is expected that commercial manifestation of some of the approaches discussed here will take place. The future of zeolite-based sensors will continue to exploit its unique properties and use of other microporous frameworks, including metal organic frameworks. Zeolite composites with electronic materials, including metals will lead to new paradigms in sensing. Use of nano-sized zeolite crystals and zeolite membranes will enhance sensor properties and make possible new routes of miniaturized sensors.

  2. Exploitation of Unique Properties of Zeolites in the Development of Gas Sensors

    Directory of Open Access Journals (Sweden)

    Prabir K. Dutta

    2012-04-01

    Full Text Available The unique properties of microporous zeolites, including ion-exchange properties, adsorption, molecular sieving, catalysis, conductivity have been exploited in improving the performance of gas sensors. Zeolites have been employed as physical and chemical filters to improve the sensitivity and selectivity of gas sensors. In addition, direct interaction of gas molecules with the extraframework cations in the nanoconfined space of zeolites has been explored as a basis for developing new impedance-type gas/vapor sensors. In this review, we summarize how these properties of zeolites have been used to develop new sensing paradigms. There is a considerable breadth of transduction processes that have been used for zeolite incorporated sensors, including frequency measurements, optical and the entire gamut of electrochemical measurements. It is clear from the published literature that zeolites provide a route to enhance sensor performance, and it is expected that commercial manifestation of some of the approaches discussed here will take place. The future of zeolite-based sensors will continue to exploit its unique properties and use of other microporous frameworks, including metal organic frameworks. Zeolite composites with electronic materials, including metals will lead to new paradigms in sensing. Use of nano-sized zeolite crystals and zeolite membranes will enhance sensor properties and make possible new routes of miniaturized sensors.

  3. Silicon photonic dual-gas sensor for H2 and CO2 detection.

    Science.gov (United States)

    Mi, Guangcan; Horvath, Cameron; Van, Vien

    2017-07-10

    We report a silicon photonic dual-gas sensor based on a wavelength-multiplexed microring resonator array for simultaneous detection of H2 and CO2 gases. The sensor uses Pd as the sensing layer for H2 gas and a novel functional material based on the Polyhexamethylene Biguanide (PHMB) polymer for CO2 gas sensing. Gas sensing experiments showed that the PHMB-functionalized microring exhibited high sensitivity to CO2 gas and excellent selectivity against H2. However, the Pd-functionalized microring was found to exhibit sensitivity to both H2 and CO2 gases, rendering it ineffective for detecting H2 in a gas mixture containing CO2. We show that the dual-gas sensing scheme can allow for accurate measurement of H2 concentration in the presence of CO2 by accounting for the cross-sensitivity of Pd to the latter.

  4. Gas-sensing enhancement methods for hydrothermal synthesized SnO2-based sensors

    Science.gov (United States)

    Zhao, Yalei; Zhang, Wenlong; Yang, Bin; Liu, Jingquan; Chen, Xiang; Wang, Xiaolin; Yang, Chunsheng

    2017-11-01

    Gas sensing for hydrothermal synthesized SnO2-based gas sensors can be enhanced in three ways: structural improvement, composition optimization, and processing improvement. There have been zero-dimensional, one-dimensional, and three-dimensional structures reported in the literature. Controllable synthesis of different structures has been deployed to increase specific surface area. Change of composition would intensively tailor the SnO2 structure, which affected the gas-sensing performance. Furthermore, doping and compounding methods have been adopted to promote gas-sensing performance by adjusting surface conditions of SnO2 crystals and constructing heterojunctions. As for processing area, it is very important to find the optimal reaction time and temperature. In this paper, a gas-solid reaction rate constant was proposed to evaluate gas-sensing properties and find an excellent hydrothermal synthesized SnO2-based gas sensor.

  5. The electromagnetic-trait imaging computation of traveling wave method in breast tumor microwave sensor system.

    Science.gov (United States)

    Tao, Zhi-Fu; Han, Zhong-Ling; Yao, Meng

    2011-01-01

    Using the difference of dielectric constant between malignant tumor tissue and normal breast tissue, breast tumor microwave sensor system (BRATUMASS) determines the detected target of imaging electromagnetic trait by analyzing the properties of target tissue back wave obtained after near-field microwave radicalization (conelrad). The key of obtained target properties relationship and reconstructed detected space is to analyze the characteristics of the whole process from microwave transmission to back wave reception. Using traveling wave method, we derive spatial transmission properties and the relationship of the relation detected points distances, and valuate the properties of each unit by statistical valuation theory. This chapter gives the experimental data analysis results.

  6. Strain Wave Acquisition by a Fiber Optic Coherent Sensor for Impact Monitoring

    Directory of Open Access Journals (Sweden)

    Claudio Sbarufatti

    2017-07-01

    Full Text Available A novel fiber optic sensing technology for high frequency dynamics detection is proposed in this paper, specifically tailored for structural health monitoring applications based on strain wave analysis, for both passive impact identification and active Lamb wave monitoring. The sensing solution relies on a fiber optic-based interferometric architecture associated to an innovative coherent detection scheme, which retrieves in a completely passive way the high-frequency phase information of the received optical signal. The sensing fiber can be arranged into different layouts, depending on the requirement of the specific application, in order to enhance the sensor sensitivity while still ensuring a limited gauge length if punctual measures are required. For active Lamb wave monitoring, this results in a sensing fiber arranged in multiple loops glued on an aluminum thin panel in order to increase the phase signal only in correspondence to the sensing points of interest. Instead, for passive impact identification, the required sensitivity is guaranteed by simply exploiting a longer gauge length glued to the structure. The fiber optic coherent (FOC sensor is exploited to detect the strain waves emitted by a piezoelectric transducer placed on the aluminum panel or generated by an impulse hammer, respectively. The FOC sensor measurements have been compared with both a numerical model based on Finite Elements and traditional piezoelectric sensors, confirming a good agreement between experimental and simulated results for both active and passive impact monitoring scenarios.

  7. Strain Wave Acquisition by a Fiber Optic Coherent Sensor for Impact Monitoring.

    Science.gov (United States)

    Sbarufatti, Claudio; Beligni, Alessio; Gilioli, Andrea; Ferrario, Maddalena; Mattarei, Marco; Martinelli, Mario; Giglio, Marco

    2017-07-13

    A novel fiber optic sensing technology for high frequency dynamics detection is proposed in this paper, specifically tailored for structural health monitoring applications based on strain wave analysis, for both passive impact identification and active Lamb wave monitoring. The sensing solution relies on a fiber optic-based interferometric architecture associated to an innovative coherent detection scheme, which retrieves in a completely passive way the high-frequency phase information of the received optical signal. The sensing fiber can be arranged into different layouts, depending on the requirement of the specific application, in order to enhance the sensor sensitivity while still ensuring a limited gauge length if punctual measures are required. For active Lamb wave monitoring, this results in a sensing fiber arranged in multiple loops glued on an aluminum thin panel in order to increase the phase signal only in correspondence to the sensing points of interest. Instead, for passive impact identification, the required sensitivity is guaranteed by simply exploiting a longer gauge length glued to the structure. The fiber optic coherent (FOC) sensor is exploited to detect the strain waves emitted by a piezoelectric transducer placed on the aluminum panel or generated by an impulse hammer, respectively. The FOC sensor measurements have been compared with both a numerical model based on Finite Elements and traditional piezoelectric sensors, confirming a good agreement between experimental and simulated results for both active and passive impact monitoring scenarios.

  8. Studies on a surface acoustic wave (SAW) dosimeter sensor for organophosphorous nerve agents

    NARCIS (Netherlands)

    Nieuwenhuizen, M.S.; Harteveld, J.L.N.

    1997-01-01

    As a follow-up of previous work on a Surface Acoustic Wave (SAW) sensor for nerve agents, irreversible response effects have been studied in more detail. Surface analytical studies indicated that degradation products are responsible for the effects observed. In addition it was tried to explore these

  9. Thermal-wave balancing flow sensor with low-drift power feedback

    NARCIS (Netherlands)

    Dijkstra, Marcel; Lammerink, Theodorus S.J.; Pjetri, O.; de Boer, Meint J.; Berenschot, Johan W.; Wiegerink, Remco J.; Elwenspoek, Michael Curt

    2014-01-01

    A control system using a low-drift power-feedback signal was implemented applying thermal waves, giving a sensor output independent of resistance drift and thermo-electric offset voltages on interface wires. Kelvin-contact sensing and power control is used on heater resistors, thereby inhibiting the

  10. The quality of our drinking water: aluminium determination with an acoustic wave sensor.

    Science.gov (United States)

    Veríssimo, Marta I S; Gomes, M Teresa S R

    2008-06-09

    A new methodology based on an inexpensive aluminium acoustic wave sensor is presented. Although the aluminium sensor has already been reported, and the composition of the selective membrane is known, the low detection limits required for the analysis of drinking water, demanded the inclusion of a preconcentration stage, as well as an optimization of the sensor. The necessary coating amount was established, as well as the best preconcentration protocol, in terms of oxidation of organic matter and aluminium elution from the Chelex-100. The methodology developed with the acoustic wave sensor allowed aluminium quantitation above 0.07 mg L(-1). Several water samples from Portugal were analysed using the acoustic wave sensor, as well as by UV-vis spectrophotometry. Results obtained with both methodologies were not statistically different (alpha=0.05), both in terms of accuracy and precision. This new methodology proved to be adequate for aluminium quantitation in drinking water and showed to be faster and less reagent consuming than the UV spectrophotometric methodology.

  11. Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

    Science.gov (United States)

    Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal

    2014-03-01

    Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

  12. PDMS membranes as sensing element in optical sensors for gas detection in water

    Directory of Open Access Journals (Sweden)

    Stefania Torino

    2017-11-01

    Full Text Available Polydimethylsiloxane (PDMS has been introduced the first time about 20years ago. This polymer is worldwide used for the rapid prototyping of microfluidic device through a replica molding process. However, the great popularity of PDMS is not only related to its easy processability, but also to its chemical and physical properties. For its interesting properties, the polymer has been implied for several applications, including sensing. In this work, we investigated how to use functionalized PDMS membranes as sensing elements in optical sensors for gas detection in water samples. Keywords: Polydimethylsiloxane (PDMS, Surface Plasmon Resonance (SPR sensors, Gas sensor

  13. METHOD FOR DETERMINATION OF THE CHARACTERISTIC CURVE OF THE THERMAL INERTIA OF AIRCRAFT GAS TEMPERATURE SENSORS

    Directory of Open Access Journals (Sweden)

    A. F. Sabitov

    2017-01-01

    Full Text Available The effectiveness of correction of the dynamic characteristics of gas temperature sensors in automatic control systems for the operation of aircraft gas turbine engines depends on the accuracy of the time constants of the sensors used from heat exchange conditions. The aim of this work was to develop a new method for determining the characteristic curves of the thermal inertia of gas temperature sensors.The new technique does not require finding the time constants of gas temperature sensors on the experimental transient characteristics. Characteristic curves for each time constant are defined as hyperbolic dependencies on the heat transfer coefficient of the gas temperature sensors sensing element with the gas flow. Parameters of hyperbolic dependencies are proposed to be established using two-dimensional regression analysis. For this purpose, special software has been developed in the Mathcad 14 and Mathcad 15. The software allows inputting the original data from the transient characteristics to the corresponding vectors or from tables in Excel format. It is shown that the transient characteristics in three-dimensional coordinates«time – heat transfer coefficient – the value of the transition characteristic» form a surface whose parameters are parameters of the desired hyperbolic dependencies.For a specific application of the technique, the regression functions for the dynamic characteristics of gas temperature sensors corresponding to the first and second orders are given. Analysis of the characteristic dependencies suggests that the proposed method more accurately establishes the dependence of the dynamic characteristics of aircraft gas temperature sensors on heat exchange conditions.It is shown that the algorithm of two-dimensional regression analysis realizes finding more accurate values of the parameters of the characteristic dependencies. The found parameters of the characteristic dependencies in a best way reach the surface of the

  14. Improved Correction Localization Algorithm Based on Wave Direction Spectrum for Underwater Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Zhang Ming

    2014-09-01

    Full Text Available Localization is an important topic in the underwater wireless sensor networks (UWSN because sensor nodes are randomly scattered over a region and can get connected into a network on their own. In this paper, we proposed an improved correction localization algorithm based on wave direction spectrum for underwater wireless sensor networks. First, we use the length of anchor nodes and depth of nodes to compute the radius and achieve the initial positioning. Second, we estimate the moving distance of nodes through analyzing the wave direction spectrum, the correction coefficient was computed for X-axis, Y-axis, Z-axis respectively to correct the coordinate. Simulation shows that the localization accuracy of the proposed algorithm is better under the same time and speed environment than USP algorithm and SLMP algorithm.

  15. Super high sensitive plate acoustic wave humidity sensor based on graphene oxide film.

    Science.gov (United States)

    Kuznetsova, Iren E; Anisimkin, Vladimir I; Gubin, Sergei P; Tkachev, Sergei V; Kolesov, Vladimir V; Kashin, Vadim V; Zaitsev, Boris D; Shikhabudinov, Alexander M; Verona, Enrico; Sun, Shaorong

    2017-11-01

    The changes of density and elastic modules due to water vapor adsorption are measured for graphene oxide film at room temperature. Dominant mechanism for acoustic wave humidity sensing by the film is shown to be related with variation of its electric conductivity. Basing on the data, super high sensitive humidity sensor employing high-order Lamb wave with large coupling constant, standard lithium niobate plate, and graphene oxide sorbent film is developed. The minimal detectable level of the sensor is as low 0.03% RH, response times are 60/120s, and reproducibility is ±2.5%. The sensor is completely selective towards H2, CO, CH4, NO, O2. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. THIN FILM-BASED SENSOR FOR MOTOR VEHICLE EXHAUST GAS, NH3, AND CO DETECTION

    Directory of Open Access Journals (Sweden)

    S. Sujarwata

    2016-10-01

    Full Text Available A copper phthalocyanine (CuPc thin film based gas sensor with FET structure and channel length 100 μm has been prepared by VE method and lithography technique to detect NH3, motor cycle exhaust gases and CO. CuPc material layer was deposited on SiO2 by the vacuum evaporator (VE method at room temperature and pressure of 8 x10-4 Pa. The stages of manufacturing gas sensor were Si/SiO2 substrate blenching with ethanol in an ultrasonic cleaner, source, and drain electrodes deposition on the substrate by using a vacuum evaporator, thin film deposition between the source/drain and gate deposition. The sensor response times to NH3, motorcycle exhaust gases and CO were 75 s, 135 s, and 150, respectively. The recovery times were 90 s, 150 s and 225, respectively. It is concluded that the CuPc thin film-based gas sensor with FET structure is the best sensor to detect the NH3 gas.Sensor gas berbasis film tipis copper phthalocyanine (CuPc berstruktur FET dengan panjang channel 100 μm telah dibuatdengan metode VE dan teknik lithography untuk mendeteksi NH3 gas buang kendaraan bermotor dan CO. Lapisan bahan CuPc dideposisikan pada permukaan silikon dioksida (SiO2 dengan metode vacuum evaporator (VE pada temperatur ruang dengan tekanan 8 x10-4 Pa. Tahapan pembuatan sensor gas adalah pencucian substrat Si/SiO2 dengan etanol dalam ultrasonic cleaner, deposisi elektroda source dan drain di atas substrat dengan metode vacuum evaporator, deposisi film tipis diantara source/drain dan deposisi gate. Waktu tanggap sensor terhadap NH3, gas buang kendaraan bermotor dan CO berturut-turut adalah 75 s, 135 s,dan 150 s. Waktu pemulihan berturut-turut adalah 90 s, 150 s,dan 225 s. Disimpulkan bahwa sensor gas berstruktur FET berbasis film tipis CuPc merupakan sensor paling baik untuk mendeteksi adanya gas NH3.

  17. Determination of bacterial activity by use of an evanescent-wave fiber-optic sensor

    Science.gov (United States)

    John, M. Shelly; Kishen, Anil; Sing, Lim Chu; Asundi, Anand

    2002-12-01

    A novel technique based on fiber-optic evanescent-wave spectroscopy is proposed for the detection of bacterial activity in human saliva. The sensor determines the specific concentration of Streptococcus mutans in saliva, which is a major causative factor in dental caries. In this design, one prepares the fiber-optic bacterial sensor by replacing a portion of the cladding region of a multimode fiber with a dye-encapsulated xerogel, using the solgel technique. The exponential decay of the evanescent wave at the core-cladding interface of a multimode fiber is utilized for the determination of bacterial activity in saliva. The acidogenic profile of Streptococcus mutans is estimated by use of evanescent-wave absorption spectra at various levels of bacterial activity.

  18. Cr2O3 nanoparticle-functionalized WO3 nanorods for ethanol gas sensors

    Science.gov (United States)

    Choi, Seungbok; Bonyani, Maryam; Sun, Gun-Joo; Lee, Jae Kyung; Hyun, Soong Keun; Lee, Chongmu

    2018-02-01

    Pristine WO3 nanorods and Cr2O3-functionalized WO3 nanorods were synthesized by the thermal evaporation of WO3 powder in an oxidizing atmosphere, followed by spin-coating of the nanowires with Cr2O3 nanoparticles and thermal annealing in an oxidizing atmosphere. Scanning electron microscopy was used to examine the morphological features and X-ray diffraction was used to study the crystallinity and phase formation of the synthesized nanorods. Gas sensing tests were performed at different temperatures in the presence of test gases (ethanol, acetone, CO, benzene and toluene). The Cr2O3-functionalized WO3 nanorods sensor showed a stronger response to these gases relative to the pristine WO3 nanorod sensor. In particular, the response of the Cr2O3-functionalized WO3 nanorods sensor to 200 ppm ethanol gas was 5.58, which is approximately 4.4 times higher that of the pristine WO3 nanorods sensor. Furthermore, the Cr2O3-functionalized WO3 nanorods sensor had a shorter response and recovery time. The pristine WO3 nanorods had no selectivity toward ethanol gas, whereas the Cr2O3-functionalized WO3 nanorods sensor showed good selectivity toward ethanol. The gas sensing mechanism of the Cr2O3-functionalized WO3 nanorods sensor toward ethanol is discussed in detail.

  19. Approach for Self-Calibrating CO2 Measurements with Linear Membrane-Based Gas Sensors

    Directory of Open Access Journals (Sweden)

    Detlef Lazik

    2016-11-01

    Full Text Available Linear membrane-based gas sensors that can be advantageously applied for the measurement of a single gas component in large heterogeneous systems, e.g., for representative determination of CO2 in the subsurface, can be designed depending on the properties of the observation object. A resulting disadvantage is that the permeation-based sensor response depends on operating conditions, the individual site-adapted sensor geometry, the membrane material, and the target gas component. Therefore, calibration is needed, especially of the slope, which could change over several orders of magnitude. A calibration-free approach based on an internal gas standard is developed to overcome the multi-criterial slope dependency. This results in a normalization of sensor response and enables the sensor to assess the significance of measurement. The approach was proofed on the example of CO2 analysis in dry air with tubular PDMS membranes for various CO2 concentrations of an internal standard. Negligible temperature dependency was found within an 18 K range. The transformation behavior of the measurement signal and the influence of concentration variations of the internal standard on the measurement signal were shown. Offsets that were adjusted based on the stated theory for the given measurement conditions and material data from the literature were in agreement with the experimentally determined offsets. A measurement comparison with an NDIR reference sensor shows an unexpectedly low bias (<1% of the non-calibrated sensor response, and comparable statistical uncertainty.

  20. Approach for Self-Calibrating CO2 Measurements with Linear Membrane-Based Gas Sensors

    Science.gov (United States)

    Lazik, Detlef; Sood, Pramit

    2016-01-01

    Linear membrane-based gas sensors that can be advantageously applied for the measurement of a single gas component in large heterogeneous systems, e.g., for representative determination of CO2 in the subsurface, can be designed depending on the properties of the observation object. A resulting disadvantage is that the permeation-based sensor response depends on operating conditions, the individual site-adapted sensor geometry, the membrane material, and the target gas component. Therefore, calibration is needed, especially of the slope, which could change over several orders of magnitude. A calibration-free approach based on an internal gas standard is developed to overcome the multi-criterial slope dependency. This results in a normalization of sensor response and enables the sensor to assess the significance of measurement. The approach was proofed on the example of CO2 analysis in dry air with tubular PDMS membranes for various CO2 concentrations of an internal standard. Negligible temperature dependency was found within an 18 K range. The transformation behavior of the measurement signal and the influence of concentration variations of the internal standard on the measurement signal were shown. Offsets that were adjusted based on the stated theory for the given measurement conditions and material data from the literature were in agreement with the experimentally determined offsets. A measurement comparison with an NDIR reference sensor shows an unexpectedly low bias (sensor response, and comparable statistical uncertainty. PMID:27869656

  1. A Novel Particulate Matter 2.5 Sensor Based on Surface Acoustic Wave Technology

    Directory of Open Access Journals (Sweden)

    Jiuling Liu

    2018-01-01

    Full Text Available Design, fabrication and experiments of a miniature particulate matter (PM 2.5 sensor based on the surface acoustic wave (SAW technology were proposed. The sensor contains a virtual impactor (VI for particle separation, a thermophoretic precipitator (TP for PM2.5 capture and a SAW sensor chip for PM2.5 mass detection. The separation performance of the VI was evaluated by using the finite element method (FEM model and the PM2.5 deposition characteristic in the TP was obtained by analyzing the thermophoretic theory. Employing the coupling-of-modes (COM model, a low loss and high-quality SAW resonator was designed. By virtue of the micro electro mechanical system (MEMS technology and semiconductor technology, the SAW based PM2.5 sensor detecting probe was fabricated. Then, combining a dual-port SAW oscillator and an air sampler, the experimental platform was set up. Exposing the PM2.5 sensor to the polystyrene latex (PSL particles in a chamber, the sensor performance was evaluated. The results show that by detecting the PSL particles with a certain diameter of 2 μm, the response of the SAW based PM2.5 sensor is linear, and in accordance with the response of the light scattering based PM2.5 monitor. The developed SAW based PM2.5 sensor has great potential for the application of airborne particle detection.

  2. A novel optimal sensitivity design scheme for yarn tension sensor using surface acoustic wave device.

    Science.gov (United States)

    Lei, Bingbing; Lu, Wenke; Zhu, Changchun; Liu, Qinghong; Zhang, Haoxin

    2014-08-01

    In this paper, we propose a novel optimal sensitivity design scheme for the yarn tension sensor using surface acoustic wave (SAW) device. In order to obtain the best sensitivity, the regression model between the size of the SAW yarn tension sensor substrate and the sensitivity of the SAW yarn tension sensor was established using the least square method. The model was validated too. Through analyzing the correspondence between the regression function monotonicity and its partial derivative sign, the effect of the SAW yarn tension sensor substrate size on the sensitivity of the SAW yarn tension sensor was investigated. Based on the regression model, a linear programming model was established to gain the optimal sensitivity of the SAW yarn tension sensor. The linear programming result shows that the maximum sensitivity will be achieved when the SAW yarn tension sensor substrate length is equal to 15 mm and its width is equal to 3mm within a fixed interval of the substrate size. An experiment of SAW yarn tension sensor about 15 mm long and 3mm wide was presented. Experimental results show that the maximum sensitivity 1982.39 Hz/g was accomplished, which confirms that the optimal sensitivity design scheme is useful and effective. Copyright © 2014. Published by Elsevier B.V.

  3. Air/fuel ratio for an internal combustion engine controlled by gas sensor in intake manifold

    Energy Technology Data Exchange (ETDEWEB)

    Barnard, D.D.

    1978-08-22

    In a closed loop fuel management system for an internal combustion engine, a gas sensor is positioned in the intake manifold and is responsive to a characteristic of the fuel mixture for generating an electrical control signal for controlling the metering of the fuel to the mixture. In the preferred embodiment, the air and fuel are mixed together and the resultant mixture passes by an oxygen gas sensor prior to being distributed to the cylinders through the intake manifold system. The output signal of the sensor is used for controlling the metering of the fuel. Fuel delivery correction delays due to transport lag in conventional closed loop fuel management systems using oxygen gas sensors are eliminated.

  4. Development and Creating of Gas-Sensor System Based on Low Dimensional Metal Oxides

    Directory of Open Access Journals (Sweden)

    Bovhyra, R.V.

    2016-11-01

    Full Text Available Peculiarities of photoluminescent properties of metal oxide nanopowders (ZnO, TiO2, SnO2, WO3 including laser-modified and surface doped by impurities (Au, Ag, Pt, Ni, Cu, Sn, in gases (О2, N2, H2, CO, CO2 were studied. Nature of sensor properties of the metal oxide nanopowders (adsorption capacity, speed, sensitivity, selectivity were established; the best structure and materials for the development of a multicomponent recording matrix were selected. The efficiency of the constructed sensor system for the gases’ and their mixtures detection and analysis was found. The developed gas sensor system allows detecting not only separate gas components, but their mixture with high sensitivity and selectivity, providing the possibility to reach the modern level of the formation of gas sensor systems with improved performance.

  5. A Micro-Resonant Gas Sensor with Nanometer Clearance between the Pole Plates.

    Science.gov (United States)

    Fu, Xiaorui; Xu, Lizhong

    2018-01-26

    In micro-resonant gas sensors, the capacitive detection is widely used because of its simple structure. However, its shortcoming is a weak signal output caused by a small capacitance change. Here, we reduced the initial clearance between the pole plates to the nanometer level, and increased the capacitance between the pole plates and its change during resonator vibration. We propose a fabricating process of the micro-resonant gas sensor by which the initial clearance between the pole plates is reduced to the nanometer level and a micro-resonant gas sensor with 200 nm initial clearance is fabricated. With this sensor, the resonant frequency shifts were measured when they were exposed to several different vapors, and high detection accuracies were obtained. The detection accuracy with respect to ethanol vapor was 0.4 ppm per Hz shift, and the detection accuracy with respect to hydrogen and ammonias vapors was 3 ppm and 0.5 ppm per Hz shift, respectively.

  6. Development of Fabric-Based Chemical Gas Sensors for Use as Wearable Electronic Noses

    Directory of Open Access Journals (Sweden)

    Thara Seesaard

    2015-01-01

    Full Text Available Novel gas sensors embroidered into fabric substrates based on polymers/ SWNT-COOH nanocomposites were proposed in this paper, aiming for their use as a wearable electronic nose (e-nose. The fabric-based chemical gas sensors were fabricated by two main processes: drop coating and embroidery. Four potential polymers (PVC, cumene-PSMA, PSE and PVP/functionalized-SWCNT sensing materials were deposited onto interdigitated electrodes previously prepared by embroidering conductive thread on a fabric substrate to make an optimal set of sensors. After preliminary trials of the obtained sensors, it was found that the sensors yielded a electrical resistance in the region of a few kilo-Ohms. The sensors were tested with various volatile compounds such as ammonium hydroxide, ethanol, pyridine, triethylamine, methanol and acetone, which are commonly found in the wastes released from the human body. These sensors were used to detect and discriminate between the body odors of different regions and exist in various forms such as the urine, armpit and exhaled breath odor. Based on a simple pattern recognition technique, we have shown that the proposed fabric-based chemical gas sensors can discriminate the human body odor from two persons.

  7. An Annular Mechanical Temperature Compensation Structure for Gas-Sealed Capacitive Pressure Sensor

    Science.gov (United States)

    Hao, Xiuchun; Jiang, Yonggang; Takao, Hidekuni; Maenaka, Kazusuke; Higuchi, Kohei

    2012-01-01

    A novel gas-sealed capacitive pressure sensor with a temperature compensation structure is reported. The pressure sensor is sealed by Au-Au diffusion bonding under a nitrogen ambient with a pressure of 100 kPa and integrated with a platinum resistor-based temperature sensor for human activity monitoring applications. The capacitance-pressure and capacitance-temperature characteristics of the gas-sealed capacitive pressure sensor without temperature compensation structure are calculated. It is found by simulation that a ring-shaped structure on the diaphragm of the pressure sensor can mechanically suppress the thermal expansion effect of the sealed gas in the cavity. Pressure sensors without/with temperature compensation structures are fabricated and measured. Through measured results, it is verified that the calculation model is accurate. Using the compensation structures with a 900 μm inner radius, the measured temperature coefficient is much reduced as compared to that of the pressure sensor without compensation. The sensitivities of the pressure sensor before and after compensation are almost the same in the pressure range from 80 kPa to 100 kPa. PMID:22969385

  8. Establishment and Application of Coalmine Gas Prediction Model Based on Multi-Sensor Data Fusion Technology

    Directory of Open Access Journals (Sweden)

    Wenyu Lv

    2014-04-01

    Full Text Available Undoubtedly an accident involving gas is one of the greater disasters that can occur in a coalmine, thus being able to predict when an accident involving gas might occur is an essential aspect in loss prevention and the reduction of safety hazards. However, the traditional methods concerning gas safety prediction is hindered by multi-objective and non-continuous problem. The coalmine gas prediction model based on multi-sensor data fusion technology (CGPM-MSDFT was established through analysis of accidents involving gas using artificial neural network to fuse multi- sensor data, using an improved algorithm designed to train the network and using an early stop method to resolve the over-fitting problem, the network test and field application results show that this model can provide a new direction for research into predicting the likelihood of a gas related incident within a coalmine. It will have a broad application prospect in coal mining.

  9. Semiconductor device-based sensors for gas, chemical, and biomedical applications

    CERN Document Server

    Ren, Fan

    2011-01-01

    Sales of U.S. chemical sensors represent the largest segment of the multi-billion-dollar global sensor market, which includes instruments for chemical detection in gases and liquids, biosensors, and medical sensors. Although silicon-based devices have dominated the field, they are limited by their general inability to operate in harsh environments faced with factors such as high temperature and pressure. Exploring how and why these instruments have become a major player, Semiconductor Device-Based Sensors for Gas, Chemical, and Biomedical Applications presents the latest research, including or

  10. Biochemical sensing application based on optical fiber evanescent wave sensor

    Science.gov (United States)

    Lv, Xiaoyi; Mo, Jiaqing; Xu, Liang; Jia, Zhenhong

    2015-08-01

    We have designed a novel evanescent field fiber optic biosensors with porous silicon dioxide cladding. The pore size of porous silicon dioxide cladding is about 100 nm in diameter. Biological molecules were immobilized to the porous silicon dioxide cladding used APTES and glutaraldehyde. Refractive index of cladding used Bruggemann's effective medium theory. We carried out simulations of changing in light intensity in optical fiber before and after chemical coupling of biomolecules. This novel optical fiber evanescent wave biosensor has a great potential in clinical chemistry for rapid and convenient determination of biological molecule.

  11. Silicon Carbide-Based Hydrogen Gas Sensors for High-Temperature Applications

    Directory of Open Access Journals (Sweden)

    Sangchoel Kim

    2013-10-01

    Full Text Available We investigated SiC-based hydrogen gas sensors with metal-insulator-semiconductor (MIS structure for high temperature process monitoring and leak detection applications in fields such as the automotive, chemical and petroleum industries. In this work, a thin tantalum oxide (Ta2O5 layer was exploited with the purpose of sensitivity improvement, because tantalum oxide has good stability at high temperature with high permeability for hydrogen gas. Silicon carbide (SiC was used as a substrate for high-temperature applications. We fabricated Pd/Ta2O5/SiC-based hydrogen gas sensors, and the dependence of their I-V characteristics and capacitance response properties on hydrogen concentrations were analyzed in the temperature range from room temperature to 500 °C. According to the results, our sensor shows promising performance for hydrogen gas detection at high temperatures.

  12. Silicon carbide-based hydrogen gas sensors for high-temperature applications.

    Science.gov (United States)

    Kim, Seongjeen; Choi, Jehoon; Jung, Minsoo; Joo, Sungjae; Kim, Sangchoel

    2013-10-09

    We investigated SiC-based hydrogen gas sensors with metal-insulator-semiconductor (MIS) structure for high temperature process monitoring and leak detection applications in fields such as the automotive, chemical and petroleum industries. In this work, a thin tantalum oxide (Ta2O5) layer was exploited with the purpose of sensitivity improvement, because tantalum oxide has good stability at high temperature with high permeability for hydrogen gas. Silicon carbide (SiC) was used as a substrate for high-temperature applications. We fabricated Pd/Ta2O5/SiC-based hydrogen gas sensors, and the dependence of their I-V characteristics and capacitance response properties on hydrogen concentrations were analyzed in the temperature range from room temperature to 500 °C. According to the results, our sensor shows promising performance for hydrogen gas detection at high temperatures.

  13. Selective differential ammonia gas sensor based on N-doped SWCNT films

    Energy Technology Data Exchange (ETDEWEB)

    Battie, Yann; Loiseau, Annick [LEM ONERA-CNRS UMR 104, 29 Av. de la Division Leclerc, 92322 Chatillon (France); Ducloux, Olivier; Thobois, Philippe [ONERA - DMPH, 29 Av. de la Division Leclerc, 92322 Chatillon (France); Susi, Toma; Kauppinen, Esko I. [NanoMaterials Group, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, 00076 Aalto, Espoo (Finland)

    2011-11-15

    The sensing performance of a micro-sensor based on a thick film of nitrogen-doped single-walled carbon nanotube (SWCNTs) is compared to a pristine SWCNTs film. Transfer length method analysis is used to extract the film sheet resistance from electrical measurements and reveals that the gas sensing mechanism is mainly attributed to the charge transfer between gas molecules and SWCNTs. We demonstrate that the sensitivity to NH{sub 3} can be improved by using a sensor based N-doped SWCNTs films while the sensitivity to NO{sub 2} and water vapour is unmodified. These unique gas-sensing properties can be used to develop a new NH{sub 3}-selective differential gas sensor. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Enhancement of NH3 Gas Sensitivity at Room Temperature by Carbon Nanotube-Based Sensor Coated with Co Nanoparticles

    OpenAIRE

    Lich Quang Nguyen; Pho Quoc Phan; Chien Duc Nguyen; Huyen Ngoc Duong; Lam Huu Nguyen

    2013-01-01

    Multi-walled carbon nanotube (MWCNT) film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH3 gas sensing applications. The MWCNT-based sensor is sensitive to NH3 gas at room temperature. Nanoclusters of Co catalysts have been sputtered on the surface of the MWCNT film to enhance gas sensitivity with respect to unfunctionalized CNT films. The gas sensitivity of Co-functionalized MWCNT-based gas sensors is thus significantly improved. The...

  15. Molecular-Resonance Fiber Optic Gas Sensors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Aspen systems proposes to develop an innovative and smart sensors to continuously monitor ambient air compositions by utilizing a resonating tunable micro-cavity...

  16. Inductive sensors for blade tip-timing in gas turbines

    Directory of Open Access Journals (Sweden)

    Przysowa Radosław

    2015-12-01

    Full Text Available The paper reviews features and applications of the upgraded inductive sensor for BTT, which is able to operate in contact with exhaust gases of temperature even as high as 1200 K. The new design includes metal-ceramic housing ensuring proper heat transfer, magnetic circuit containing set of permanent magnets with various magnetic field values and Curie temperatures, completely redesigned windings and current/voltage converter used instead of an electromotive force amplifier. Its principle of operation is based on electro-dynamical interaction and therefore it may be referred as a passive eddy-current sensor. The sensor technique has been demonstrated on four stages of a surplus military turbofan including the high pressure turbine as part of the engine health monitoring system. We present signal samples and review methods used for online processing of time-of-arrival signals when only a limited number of sensors is available.

  17. Analysis of Simulated Output Characteristics of Gas Sensor Based on Graphene Nanoribbon

    Directory of Open Access Journals (Sweden)

    A. Mahmoudi

    2016-01-01

    Full Text Available This work presents simulated output characteristics of gas sensor transistors based on graphene nanoribbon (GNRFET. The device studied in this work is a new generation of gas sensing devices, which are easy to use, ultracompact, ultrasensitive, and highly selective. We will explain how the exposure to the gas changes the conductivity of graphene nanoribbon. The equations of the GNRFET gas sensor model include the Poisson equation in the weak nonlocality approximation with proposed sensing parameters. As we have developed this model as a platform for a gas detection sensor, we will analyze the current-voltage characteristics after exposure of the GNRFET nanosensor device to NH3 gas. A sensitivity of nearly 2.7% was indicated in our sensor device after exposure of 1 ppm of NH3. The given results make GNRFET the right candidate for use in gas sensing/measuring appliances. Thus, we will investigate the effect of the channel length on the ON- and OFF-current.

  18. Multiplexed Sensor for Synthesis Gas Compsition and Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Steven Buckley; Reza Gharavi; Marco Leon

    2007-10-01

    The overall goal of this project has been to develop a highly sensitive, multiplexed TDL-based sensor for CO{sub 2}, CO, H{sub 2}O (and temperature), CH{sub 4}, H{sub 2}S, and NH{sub 3}. Such a sensor was designed with so-called 'plug-and-play' characteristics to accommodate additional sensors, and provided in situ path-integrated measurements indicative of average concentrations at speeds suitable for direct gasifier control. The project developed the sensor and culminated in a real-world test of the underlying technology behind the sensor. During the project, new underlying measurements of spectroscopic constants for all of the gases of interest performed, in custom cells built for the project. The envisioned instrument was built from scratch from component lasers, fiber optics, amplifier blocks, detectors, etc. The sensor was tested for nearly a week in an operational power plant. The products of this research are expected to have a direct impact on gasifier technology and the production of high-quality syngas, with substantial broader application to coal and other energy systems. This report is the final technical report on project DE-FG26-04NT42172. During the project we completed all of the milestones planned in the project, with a modification of milestone (7) required due to lack of funding and personnel.

  19. Full-wave receiver architecture for the homodyne motion sensor

    Science.gov (United States)

    Haugen, Peter C; Dallum, Gregory E; Welsh, Patrick A; Romero, Carlos E

    2013-11-19

    A homodyne motion sensor or detector based on ultra-wideband radar utilizes the entire received waveform through implementation of a voltage boosting receiver. The receiver includes a receiver input and a receiver output. A first diode is connected to the receiver output. A first charge storage capacitor is connected from between the first diode and the receiver output to ground. A second charge storage capacitor is connected between the receiver input and the first diode. A second diode is connected from between the second charge storage capacitor and the first diode to ground. The dual diode receiver performs voltage boosting of a RF signal received at the receiver input, thereby enhancing receiver sensitivity.

  20. Content-Based Multi-Channel Network Coding Algorithm in the Millimeter-Wave Sensor Network.

    Science.gov (United States)

    Lin, Kai; Wang, Di; Hu, Long

    2016-07-01

    With the development of wireless technology, the widespread use of 5G is already an irreversible trend, and millimeter-wave sensor networks are becoming more and more common. However, due to the high degree of complexity and bandwidth bottlenecks, the millimeter-wave sensor network still faces numerous problems. In this paper, we propose a novel content-based multi-channel network coding algorithm, which uses the functions of data fusion, multi-channel and network coding to improve the data transmission; the algorithm is referred to as content-based multi-channel network coding (CMNC). The CMNC algorithm provides a fusion-driven model based on the Dempster-Shafer (D-S) evidence theory to classify the sensor nodes into different classes according to the data content. By using the result of the classification, the CMNC algorithm also provides the channel assignment strategy and uses network coding to further improve the quality of data transmission in the millimeter-wave sensor network. Extensive simulations are carried out and compared to other methods. Our simulation results show that the proposed CMNC algorithm can effectively improve the quality of data transmission and has better performance than the compared methods.

  1. Content-Based Multi-Channel Network Coding Algorithm in the Millimeter-Wave Sensor Network

    Directory of Open Access Journals (Sweden)

    Kai Lin

    2016-07-01

    Full Text Available With the development of wireless technology, the widespread use of 5G is already an irreversible trend, and millimeter-wave sensor networks are becoming more and more common. However, due to the high degree of complexity and bandwidth bottlenecks, the millimeter-wave sensor network still faces numerous problems. In this paper, we propose a novel content-based multi-channel network coding algorithm, which uses the functions of data fusion, multi-channel and network coding to improve the data transmission; the algorithm is referred to as content-based multi-channel network coding (CMNC. The CMNC algorithm provides a fusion-driven model based on the Dempster-Shafer (D-S evidence theory to classify the sensor nodes into different classes according to the data content. By using the result of the classification, the CMNC algorithm also provides the channel assignment strategy and uses network coding to further improve the quality of data transmission in the millimeter-wave sensor network. Extensive simulations are carried out and compared to other methods. Our simulation results show that the proposed CMNC algorithm can effectively improve the quality of data transmission and has better performance than the compared methods.

  2. Gas chromatograph-surface acoustic wave for quick real-time assessment of blood/exhaled gas ratio of propofol in humans.

    Science.gov (United States)

    Chen, X; Zhang, X L; Liu, L; Chen, Y; Piao, M Y; Zhang, F J; Wu, W D; Zhong, Y B; Sun, K; Zou, Y C; Zhang, X; Wang, D; Wang, P; Yan, M

    2014-11-01

    Although pilot studies have reported that exhaled propofol concentrations can reflect intraoperative plasma propofol concentrations in an individual, the blood/exhaled partial pressure ratio RBE varies between patients, and the relevant factors have not yet been clearly addressed. No efficient method has been reported for the quick evaluation of RBE and its association with inter-individual variables. We proposed a novel method that uses a surface acoustic wave (SAW) sensor combined with a fast gas chromatograph (GC) to simultaneously detect propofol concentrations in blood and exhaled gas in 28 patients who were receiving propofol i.v. A two-compartment pharmacokinetic (PK) model was established to simulate propofol concentrations in exhaled gas and blood after a bolus injection. Simulated propofol concentrations for exhaled gas and blood were used in a linear regression model to evaluate RBE. The fast GC-SAW system showed reliability and efficiency for simultaneous quantitative determination of propofol in blood (correlation coefficient R(2)=0.994, Pgas (R(2)=0.991, Panalysis of blood propofol concentrations. The proposed method allows early determination of the coefficient RBE in individuals. Further studies are required to quantify the distribution of RBE in a larger cohort and assess the effect of other potential factors. ChiCTR-ONC-13003291. © The Author 2014. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  3. Chemical Vapor Identification by Plasma Treated Thick Film Tin Oxide Gas Sensor Array and Pattern Recognition

    Directory of Open Access Journals (Sweden)

    J. K. Srivastava

    2011-02-01

    Full Text Available Present study deals the class recognition potential of a four element plasma treated thick film tin oxide gas sensor array exposed with volatile organic compounds (VOCs. Methanol, Ethanol and Acetone are selected as target VOCs and exposed on sensor array at different concentration in range from 100-1000 ppm. Sensor array consist of four tin oxide sensors doped with 1-4 % PbO concentrations were fabricated by thick film technology and then treated with oxygen plasma for 5-10 minute durations. Sensor signal is analyzed by principal component analysis (PCA for visual classification of VOCs. Further output of PCA is used as input for classification of VOCs by four pattern classification techniques as: linear discriminant analysis (LDA, k-nearest neighbor (KNN, back propagation neural network (BPNN and support vector machine (SVM. All the four classifier results 100 % correct classification rate of VOCs by response analysis of sensor array treated with plasma for 5 minute.

  4. A classification and ranking system on the H2 gas sensing capabilities of nanomaterials based on proposed coefficients of sensor performance and sensor efficiency equations

    CSIR Research Space (South Africa)

    Mwakikunga, BW

    2013-07-01

    Full Text Available Sensors and Actuators B 184 (2013) 170– 178 A classification and ranking system on the H2 gas sensing capabilities of nanomaterials based on proposed coefficients of sensor performance and sensor efficiency equations Bonex W. Mwakikungaa,b,∗, Sarah...

  5. High-sensitivity four-layer polymer fiber-optic evanescent wave sensor.

    Science.gov (United States)

    Xin, Xin; Zhong, Nianbing; Liao, Qiang; Cen, Yanyan; Wu, Ruohua; Wang, Zhengkun

    2017-05-15

    We present a novel four-layer structure consisting of bottom, second, third, and surface layers in the sensing region, for a D-shaped step-index fiber-optic evanescent wave (FOEW) sensor. To reduce the background noise, the surface of the longitudinal section in the D-shaped region is coated with a light-absorbing film. We check the morphologies of the second and surface layers, examine the refractive indices (RIs) of the third and surface layers, and analyze the composition of the surface layer. We also investigate the effects of the thicknesses and RIs of the third and surface layers and the LA film on the light transmission and sensitivity of the FOEW sensors. The results highlight the very good sensitivity of the proposed FOEW sensor with a four-layer structure, which reached -0.077 (μg/l)(-1) in the detection of the target antibody; the sensitivity of the novel FOEW sensor was 7.60 and 1.52 times better than that of a conventional sensor with a core-cladding structure and an FOEW sensor with a three-layer structure doped with GeO2. The applications of this high-sensitivity FOEW sensor can be extended to biodefense, disease diagnosis, and biomedical and biochemical analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. An Electronic-Nose Sensor Node Based on a Polymer-Coated Surface Acoustic Wave Array for Wireless Sensor Network Applications

    Directory of Open Access Journals (Sweden)

    Kea-Tiong Tang

    2011-04-01

    Full Text Available This study developed an electronic-nose sensor node based on a polymer-coated surface acoustic wave (SAW sensor array. The sensor node comprised an SAW sensor array, a frequency readout circuit, and an Octopus II wireless module. The sensor array was fabricated on a large K2 128° YX LiNbO3 sensing substrate. On the surface of this substrate, an interdigital transducer (IDT was produced with a Cr/Au film as its metallic structure. A mixed-mode frequency readout application specific integrated circuit (ASIC was fabricated using a TSMC 0.18 μm process. The ASIC output was connected to a wireless module to transmit sensor data to a base station for data storage and analysis. This sensor node is applicable for wireless sensor network (WSN applications.

  7. An electronic-nose sensor node based on a polymer-coated surface acoustic wave array for wireless sensor network applications.

    Science.gov (United States)

    Tang, Kea-Tiong; Li, Cheng-Han; Chiu, Shih-Wen

    2011-01-01

    This study developed an electronic-nose sensor node based on a polymer-coated surface acoustic wave (SAW) sensor array. The sensor node comprised an SAW sensor array, a frequency readout circuit, and an Octopus II wireless module. The sensor array was fabricated on a large K(2) 128° YX LiNbO3 sensing substrate. On the surface of this substrate, an interdigital transducer (IDT) was produced with a Cr/Au film as its metallic structure. A mixed-mode frequency readout application specific integrated circuit (ASIC) was fabricated using a TSMC 0.18 μm process. The ASIC output was connected to a wireless module to transmit sensor data to a base station for data storage and analysis. This sensor node is applicable for wireless sensor network (WSN) applications.

  8. Soil-gas helium and surface-waves detection of fault zones in ...

    Indian Academy of Sciences (India)

    gas helium; surface-waves; faults and fractures; groundwater; granite basement. ... Soil-gas helium emanometry has been utilized in Wailapally watershed,near Hyderabad in southern India,for the detection of fracture and fault zones in a granite ...

  9. Highly Efficient Gas Sensor Using a Hollow SnO2 Microfiber for Triethylamine Detection.

    Science.gov (United States)

    Zou, Yihui; Chen, Shuai; Sun, Jin; Liu, Jingquan; Che, Yanke; Liu, Xianghong; Zhang, Jun; Yang, Dongjiang

    2017-07-28

    Triethylamine (TEA) gas sensors having excellent response and selectivity are in great demand to monitor the real environment. In this work, we have successfully prepared a hollow SnO2 microfiber by a unique sustainable biomass conversion strategy and shown that the microfiber can be used in a high-performance gas sensor. The sensor based on the hollow SnO2 microfiber shows a quick response/recovery toward triethylamine. The response of the hollow SnO2 microfiber is up to 49.5 when the concentration of TEA gas is 100 ppm. The limit of detection is as low as 2 ppm. Furthermore, the sensor has a relatively low optimal operation temperature of 270 °C, which is lower than those of many other reported sensors. The excellent sensing properties are largely attributed to the high sensitivity provided by SnO2 and the good permeability and conductivity of the one-dimensional hollow structure. Thus, the hollow SnO2 microfiber using sustainable biomass as a template is a significant strategy for a unique TEA gas sensor.

  10. Fault diagnosis for micro-gas turbine engine sensors via wavelet entropy.

    Science.gov (United States)

    Yu, Bing; Liu, Dongdong; Zhang, Tianhong

    2011-01-01

    Sensor fault diagnosis is necessary to ensure the normal operation of a gas turbine system. However, the existing methods require too many resources and this need can't be satisfied in some occasions. Since the sensor readings are directly affected by sensor state, sensor fault diagnosis can be performed by extracting features of the measured signals. This paper proposes a novel fault diagnosis method for sensors based on wavelet entropy. Based on the wavelet theory, wavelet decomposition is utilized to decompose the signal in different scales. Then the instantaneous wavelet energy entropy (IWEE) and instantaneous wavelet singular entropy (IWSE) are defined based on the previous wavelet entropy theory. Subsequently, a fault diagnosis method for gas turbine sensors is proposed based on the results of a numerically simulated example. Then, experiments on this method are carried out on a real micro gas turbine engine. In the experiment, four types of faults with different magnitudes are presented. The experimental results show that the proposed method for sensor fault diagnosis is efficient.

  11. Zinc Oxide-Multi Walled Carbon Nanotubes Nanocomposites for Carbon Monoxide Gas Sensor Application.

    Science.gov (United States)

    Alharbi, Najlaa D; Ansari, M Shahnawaze; Salah, Numan; Khayyat, Suzan A; Khan, Zishan H

    2016-01-01

    Zinc oxide (ZnO)/multi walled carbon nanotubes (MWCNTs) composites based sensors with different ZnO concentrations were fabricated to improve carbon monoxide (CO) gas sensing properties in comparison to the sensors based on bare MWCNTs. To study the structure, morphology and elemental composition of the resultant products, X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) and Energy dispersive X-ray spectroscopy (EDS) were carried out. It has been observed that as the concentration of ZnO is increased more and more ZnO nanoparticles in the form of nodes get attached to MWCNTs resulting the reduction in average diameter of MWCNTs. The typical response of ZnO/MWCNTs composites based gas sensors for different CO concentrations (40, 100, 140 and 200 ppm) was studied by using very advanced sensing setup attached to I-V measurement system. Different sensing parameters such as: resistive response, sensitivity and response time were estimated at room temperature for all the fabricated sensors. The results indicated that the sensor based on nanocomposite which has 30 mg ZnO dispersed on 20 mg MWCNTs showing highest sensitivity and fastest response. All the sensors showed response times ranging from 8 to 23 seconds. The sensing mechanism behind the sensors based on ZnO/MWCNTs nanocomposites for CO gas at room temperature is also discussed in the present report.

  12. A Novel Neural Network-Based Technique for Smart Gas Sensors Operating in a Dynamic Environment

    Directory of Open Access Journals (Sweden)

    Zohir Dibi

    2009-11-01

    Full Text Available Thanks to their high sensitivity and low-cost, metal oxide gas sensors (MOX are widely used in gas detection, although they present well-known problems (lack of selectivity and environmental effects…. We present in this paper a novel neural network- based technique to remedy these problems. The idea is to create intelligent models; the first one, called corrector, can automatically linearize a sensor’s response characteristics and eliminate its dependency on the environmental parameters. The corrector’s responses are processed with the second intelligent model which has the role of discriminating exactly the detected gas (nature and concentration. The gas sensors used are industrial resistive kind (TGS8xx, by Figaro Engineering. The MATLAB environment is used during the design phase and optimization. The sensor models, the corrector, and the selective model were implemented and tested in the PSPICE simulator. The sensor model accurately expresses the nonlinear character of the response and the dependence on temperature and relative humidity in addition to their gas nature dependency. The corrector linearizes and compensates the sensor’s responses. The method discriminates qualitatively and quantitatively between seven gases. The advantage of the method is that it uses a small representative database so we can easily implement the model in an electrical simulator. This method can be extended to other sensors.

  13. Experiments of highly transient thermo-fluid dynamic phenomena in He II induced by gas dynamic shock wave impingement

    Science.gov (United States)

    Nagai, H.; Yang, H. S.; Ueta, Y.; Yanaka, K.; Murakami, M.

    2002-05-01

    Compression and thermal shock waves are generated in the superfluid shock tube facility by the impingement of a gas-dynamic shock wave propagating through helium vapor onto a He II free surface. He II can be shock-compressed to convert to He I across the λ-line in the case of He II initially at temperatures rather close to the λ-temperature. The phenomena realized in the shock tube are extremely rapid ones with a characteristic time of the order of a few microseconds. Accordingly, some advanced experimental technology is required for the measurement, and thus piezo-type pressure transducers and a superconductive temperature sensor are used for the measurement of the transient behavior. Visualization of both shock waves is successfully carried out by using an ultra-high-speed video camera with Schlieren optics. It is found from the mass velocity of bulk He II derived from a series of video images that an high Reynolds number flow, about 1.2×107, can be realized behind a compression shock wave in a very short duration. It is also an objective of the present research to make a successful transfer of experimental techniques developed in conventional thermo-fluid dynamics to cryogenic researches.

  14. Nonlinear fiber-optic strain sensor based on four-wave mixing in microstructured optical fiber

    DEFF Research Database (Denmark)

    Gu, Bobo; Yuan, Scott Wu; Frosz, Michael H.

    2012-01-01

    We demonstrate a nonlinear fiber-optic strain sensor, which uses the shifts of four-wave mixing Stokes and anti-Stokes peaks caused by the strain-induced changes in the structure and refractive index of a microstructured optical fiber. The sensor thus uses the inherent nonlinearity of the fiber...... and does not require any advanced post-processing of the fiber. Strain sensitivity of -0.23 pm/mu epsilon is achieved experimentally and numerical simulations reveal that for the present fiber the sensitivity can be increased to -4.46 pm/mu epsilon by optimizing the pump wavelength and power....

  15. Nonlinear fiber-optic strain sensor based on four-wave mixing in microstructured optical fiber.

    Science.gov (United States)

    Gu, Bobo; Yuan, Wu; Frosz, Michael H; Zhang, A Ping; He, Sailing; Bang, Ole

    2012-03-01

    We demonstrate a nonlinear fiber-optic strain sensor, which uses the shifts of four-wave mixing Stokes and anti-Stokes peaks caused by the strain-induced changes in the structure and refractive index of a microstructured optical fiber. The sensor thus uses the inherent nonlinearity of the fiber and does not require any advanced postprocessing of the fiber. Strain sensitivity of -0.23 pm/με is achieved experimentally and numerical simulations reveal that for the present fiber the sensitivity can be increased to -4.46 pm/με by optimizing the pump wavelength and power. © 2012 Optical Society of America

  16. Visualization of stress wave propagation via air-coupled acoustic emission sensors

    Science.gov (United States)

    Rivey, Joshua C.; Lee, Gil-Yong; Yang, Jinkyu; Kim, Youngkey; Kim, Sungchan

    2017-02-01

    We experimentally demonstrate the feasibility of visualizing stress waves propagating in plates using air-coupled acoustic emission sensors. Specifically, we employ a device that embeds arrays of microphones around an optical lens in a helical pattern. By implementing a beamforming technique, this remote sensing system allows us to record wave propagation events in situ via a single-shot and full-field measurement. This is a significant improvement over the conventional wave propagation tracking approaches based on laser doppler vibrometry or digital image correlation techniques. In this paper, we focus on demonstrating the feasibility and efficacy of this air-coupled acoustic emission technique by using large metallic plates exposed to external impacts. The visualization results of stress wave propagation will be shown under various impact scenarios. The proposed technique can be used to characterize and localize damage by detecting the attenuation, reflection, and scattering of stress waves that occurs at damage locations. This can ultimately lead to the development of new structural health monitoring and nondestructive evaluation methods for identifying hidden cracks or delaminations in metallic or composite plate structures, simultaneously negating the need for mounted contact sensors.

  17. Design and deployment of low-cost plastic optical fiber sensors for gas monitoring.

    Science.gov (United States)

    Grassini, Sabrina; Ishtaiwi, Maen; Parvis, Marco; Vallan, Alberto

    2014-12-30

    This paper describes an approach to develop and deploy low-cost plastic optical fiber sensors suitable for measuring low concentrations of pollutants in the atmosphere. The sensors are designed by depositing onto the exposed core of a plastic fiber thin films of sensitive compounds via either plasma sputtering or via plasma-enhanced chemical vapor deposition (PECVD). The interaction between the deposited layer and the gas alters the fiber's capability to transmit the light, so that the sensor can simply be realized with a few centimeters of fiber, an LED and a photodiode. Sensors arranged in this way exhibit several advantages in comparison to electrochemical and optical conventional sensors; in particular, they have an extremely low cost and can be easily designed to have an integral, i.e., cumulative, response. The paper describes the sensor design, the preparation procedure and two examples of sensor prototypes that exploit a cumulative response. One sensor is designed for monitoring indoor atmospheres for cultural heritage applications and the other for detecting the presence of particular gas species inside the RPC (resistive plate chamber) muon detector of the Compact Muon Solenoid (CMS) experiment at CERN in Geneva.

  18. Volatile organic compound gas sensor based on aluminum-doped zinc oxide with nanoparticle.

    Science.gov (United States)

    Choi, Nak-Jin; Lee, Hyung-Kun; Moon, Seung Eon; Yang, Woo Seok; Kim, Jongdae

    2013-08-01

    Thick film semiconductor gas sensors based on aluminum-doped zinc oxide (AZO) with nanoparticle size were fabricated to detect volatile organic compound (VOC) existed in building, especially, formaldehyde (HCHO) gas which was known as the cause of sick building syndrome. The sensing materials for screen printing were prepared using roll milling process with binder. The crystallite sizes of prepared materials were about 15 nm through X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Gas response characteristics were examined for formaldehyde (HCHO), benzene, carbon monoxide, carbon dioxide gas existing in building. In particular, the sensors showed responses to HCHO gas at sub ppm as a function of operating temperatures and gas concentrations. Also, we investigated sensitivity, repeativity, selectivity, and response time of sensor. The transients were very sharp, taking less than 2 s for 90% response. The sensor has shown very stable response at 350 degrees C and followed a very good behavior and showed 60% response in 50 ppb HCHO concentration at 350 degrees C operating temperatures.

  19. Hydrogen gas sensor based on metal oxide nanoparticles decorated graphene transistor.

    Science.gov (United States)

    Zhang, Zhangyuan; Zou, Xuming; Xu, Lei; Liao, Lei; Liu, Wei; Ho, Johnny; Xiao, Xiangheng; Jiang, Changzhong; Li, Jinchai

    2015-06-14

    In this work, in order to enhance the performance of graphene gas sensors, graphene and metal oxide nanoparticles (NPs) are combined to be utilized for high selectivity and fast response gas detection. Whether at the relatively optimal temperature or even room temperature, our gas sensors based on graphene transistors, decorated with SnO2 NPs, exhibit fast response and short recovery times (∼1 seconds) at 50 °C when the hydrogen concentration is 100 ppm. Specifically, X-ray photoelectron spectroscopy and conductive atomic force microscopy are employed to explore the interface properties between graphene and SnO2 NPs. Through the complimentary characterization, a mechanism based on charge transfer and band alignment is elucidated to explain the physical originality of these graphene gas sensors: high carrier mobility of graphene and small energy barrier between graphene and SnO2 NPs have ensured a fast response and a high sensitivity and selectivity of the devices. Generally, these gas sensors will facilitate the rapid development of next-generation hydrogen gas detection.

  20. Multipath ultrasonic gas flow-meter based on multiple reference waves.

    Science.gov (United States)

    Zhou, Hongliang; Ji, Tao; Wang, Ruichen; Ge, Xiaocheng; Tang, Xiaoyu; Tang, Shizhen

    2018-01-01

    Several technologies can be used in ultrasonic gas flow-meters, such as transit-time, Doppler, cross-correlation and etc. In applications, the approach based on measuring transit-time has demonstrated its advantages and become more popular. Among those techniques which can be applied to determine time-of-flight (TOF) of ultrasonic waves, including threshold detection, cross correlation algorithm and other digital signal processing algorithms, cross correlation algorithm has more advantages when the received ultrasonic signal is severely disturbed by the noise. However, the reference wave for cross correlation computation has great influence on the precise measurement of TOF. In the applications of the multipath flow-meters, selection of the reference wave becomes even more complicated. Based on the analysis of the impact factors that will introduce noise and waveform distortion of ultrasonic waves, an averaging method is proposed to determine the reference wave in this paper. In the multipath ultrasonic gas flow-meter, the analysis of each path of ultrasound needs its own reference wave. In case study, a six-path ultrasonic gas flow-meter has been designed and tested with air flow through the pipeline. The results demonstrate that the flow rate accuracy and the repeatability of the TOF are significantly improved by using averaging reference wave, compared with that using random reference wave. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. A microvolume molecularly imprinted polymer modified fiber-optic evanescent wave sensor for bisphenol A determination.

    Science.gov (United States)

    Xiong, Yan; Ye, Zhongbin; Xu, Jing; Liu, Yucheng; Zhang, Hanyin

    2014-04-01

    A fiber-optic evanescent wave sensor for bisphenol A (BPA) determination based on a molecularly imprinted polymer (MIP)-modified fiber column was developed. MIP film immobilized with BPA was synthesized on the fiber column, and the sensor was then constructed by inserting the optical fiber prepared into a transparent capillary. A microchannel (about 2.0 μL) formed between the fiber and the capillary acted as a flow cell. BPA can be selectively adsorbed online by the MIP film and excited to produce fluorescence by the evanescent wave produced on the fiber core surface. The conditions for BPA enrichment, elution, and fluorescence detection are discussed in detail. The analytical measurements were made at 276 nm/306 nm (λ(ex)/λ(em)), and linearity of 3 × 10(-9)-5 × 10(-6) g mL(-1) BPA, a limit of detection of 1.7 × 10(-9) g mL(-1) BPA (3σ), and a relative standard deviation of 2.4% (n = 5) were obtained. The sensor selectivity and MIP binding measurement were also evaluated. The results indicated that the selectivity and sensitivity of the proposed fiber-optic sensor could be greatly improved by using MIP as a recognition and enrichment element. Further, by modification of the sensing and detection elements on the optical fiber, the proposed sensor showed the advantages of easy fabrication and low cost. The novel sensor configuration provided a platform for monitoring other species by simply changing the light source and sensing elements. The sensor presented has been successfully applied to determine BPA released from plastic products treated at different temperatures.

  2. Design and coupled-effect simulations of CMOS micro gas sensors built on SOI thin membranes

    Science.gov (United States)

    Lu, Chih-Cheng; Udrea, Florin; Gardner, Julian W.; Setiadi, D.; Dogaru, T.; Tsai, T. H.; Covington, James A.

    2001-04-01

    This paper describes coupled-effect simulations of smart micro gas-sensors based on standard BiCMOS technology. The smart sensor features very low power consumption, high sensitivity and potential low fabrication cost achieved through full CMOS integration. For the first time the micro heaters are made of active CMOS elements (i.e. MOSFET transistors) and embedded in a thin SOI membrane consisting of Si and SiO2 thin layers. Micro gas-sensors such as chemoresistive, microcalorimeteric and Pd/polymer gate FET sensors can be made using this technology. Full numerical analyses including 3D electro- thermo-mechanical simulations, in particular stress and deflection studies on the SOI membranes are presented. The transducer circuit design and the post-CMOS fabrication process, which includes single sided back-etching, are also reported.

  3. Possibility of gas sensor based on C20 molecular devices

    Science.gov (United States)

    Zhao, Wenkai; Yang, Chuanlu; Zou, Dongqing; Sun, Zhaopeng; Ji, Guomin

    2017-06-01

    We theoretically investigate the possibility of diatomic gas detection (NO, CO, O2) by making use of the transport properties of the C20 molecular junctions. The calculations are performed by using nonequilibrium Green's function (NEGF) formalism in combination with density functional theory (DFT). In this work, we systematically study the most stable adsorption structural configurations, adsorption energy, and the transport properties on C20 molecular junctions with these diatomic gas molecules. It is found that NO and O2 gas molecule can be detected selectively. We suggest its possibility of nanosensors for highly sensitive and selective based on C20 molecular junction systems.

  4. Single ZnO Nanowire-Based Gas Sensors to Detect Low Concentrations of Hydrogen

    Directory of Open Access Journals (Sweden)

    Marlene N. Cardoza-Contreras

    2015-12-01

    Full Text Available Low concentrations of hazardous gases are difficult to detect with common gas sensors. Using semiconductor nanostructures as a sensor element is an alternative. Single ZnO nanowire gas sensor devices were fabricated by manipulation and connection of a single nanowire into a four-electrode aluminum probe in situ in a dual-beam scanning electron microscope-focused ion beam with a manipulator and a gas injection system in/column. The electrical response of the manufactured devices shows response times up to 29 s for a 121 ppm of H2 pulse, with a variation in the nanowire resistance appreciable at room temperature and at 373.15 K of approximately 8% and 14% respectively, showing that ZnO nanowires are good candidates to detect low concentrations of H2.

  5. Development of an Inexpensive RGB Color Sensor for the Detection of Hydrogen Cyanide Gas.

    Science.gov (United States)

    Greenawald, Lee A; Boss, Gerry R; Snyder, Jay L; Reeder, Aaron; Bell, Suzanne

    2017-10-27

    An inexpensive red, green, blue (RGB) color sensor was developed for detecting low ppm concentrations of hydrogen cyanide gas. A piece of glass fiber filter paper containing monocyanocobinamide [CN(H2O)Cbi] was placed directly above the RGB color sensor and an on chip LED. Light reflected from the paper was monitored for RGB color change upon exposure to hydrogen cyanide at concentrations of 1.0-10.0 ppm as a function of 25%, 50%, and 85% relative humidity. A rapid color change occurred within 10 s of exposure to 5.0 ppm hydrogen cyanide gas (near the NIOSH recommended exposure limit). A more rapid color change occurred at higher humidity, suggesting a more effective reaction between hydrogen cyanide and CN(H2O)Cbi. The sensor could provide the first real time respirator end-of-service-life alert for hydrogen cyanide gas.

  6. Room temperature CO2 gas sensors of AuNPs/mesoPSi hybrid structures

    Science.gov (United States)

    Alwan, Alwan M.; Dheyab, Amer B.

    2017-10-01

    Mesoporous silicon (mesoPSi) layer prepared by a laser-assisted etching process in HF acid has been employed as CO2 gas sensors. The surface morphology of mesoPSi was modified by embedding gold nanoparticles AuNPs by simple and quick dipping process in different gold salts concentrations to form mesoPSi/AuNPs hybrid structures. Morphology of hybrid structures was investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrical characteristics of the prepared gas sensor were carried out at room temperature. It was found that the nanoparticles size, shape and the specific surface area of the nanoparticle strongly influence the current-voltage characteristics. Considerable improvement was noticed in sensitivity, response and recovery times of gas sensor with decreasing incorporated AuNPs into the mesoPSi matrix.

  7. Highly sensitive nanostructure SnO2 based gas sensor for environmental pollutants

    Science.gov (United States)

    Korgaokar, Sushil; Moradiya, Meet; Prajapati, Om; Thakkar, Pranav; Pala, Jay; Savaliya, Chirag; Parikh, Sachin; Markna, J. H.

    2017-05-01

    A major quantity of pollutants are produced from industries and vehicles in the form of gas. New approaches are needed to solve well-known environmental pollutants like CO, CO2, NO2, SOx. Therefore detection with effective gas sensors is a vital part of pollution prevention efforts. There is a need to develop fast, rapid, cost-effective, highly sensitive, low power, and non-intrusive rugged sensors that can be easily installed. In the present study, nanostructured SnO2 used as a sensitive material in the devices and synthesized using hydrothermal process. The detailed development of the fabrication of SnO2 nanostructures gas sensor is described, which shows the remarkable change in the sensing properties with varying particle size. Additionally, we have used X-ray diffraction, scanning electron microscopy (SEM) for characterization and carefully examined the relative parameters like response magnitude (sensitivity) and selectivity of SnO2 nano structures with different particle size.

  8. Development of a standing wave apparatus for calibrating acoustic vector sensors and hydrophones.

    Science.gov (United States)

    Lenhart, Richard D; Sagers, Jason D; Wilson, Preston S

    2016-01-01

    An apparatus was developed to calibrate acoustic hydrophones and vector sensors between 25 and 2000 Hz. A standing wave field is established inside a vertically oriented, water-filled, elastic-walled waveguide by a piston velocity source at the bottom and a pressure-release boundary condition at the air/water interface. A computer-controlled linear positioning system allows a device under test to be precisely located in the water column while the acoustic response is measured. Some of the challenges of calibrating hydrophones and vector sensors in such an apparatus are discussed, including designing the waveguide to mitigate dispersion, understanding the impact of waveguide structural resonances on the acoustic field, and developing algorithms to post-process calibration measurement data performed in a standing wave field. Data from waveguide characterization experiments and calibration measurements are presented and calibration uncertainty is reported.

  9. A Novel Bulk Acoustic Wave Resonator for Filters and Sensors Applications

    Directory of Open Access Journals (Sweden)

    Zhixin Zhang

    2015-09-01

    Full Text Available Bulk acoustic wave (BAW resonators are widely applied in filters and gravimetric sensors for physical or biochemical sensing. In this work, a new architecture of BAW resonator is demonstrated, which introduces a pair of reflection layers onto the top of a thin film bulk acoustic resonator (FBAR device. The new device can be transformed between type I and type II dispersions by varying the thicknesses of the reflection layers. A computational modeling is developed to fully investigate the acoustic waves and the dispersion types of the device theoretically. The novel structure makes it feasible to fabricate both type resonators in one filter, which offers an effective alternative to improve the pass band flatness in the filter. Additionally, this new device exhibits a high quality factor (Q in the liquid, which opens a possibility for real time measurement in solutions with a superior limitation of detection (LOD in sensor applications.

  10. Improved zinc oxide film for gas sensor applications

    Indian Academy of Sciences (India)

    Unknown

    to the other CVD techniques, simultaneously yielding reasonably good quality films for sensor applications. The deposited films were confirmed to be polycrystalline zinc oxide by XRD analysis. The change in electrical resistance of the films was measured while exposing those to the different concentrations of DMA vapour.

  11. High-Density Fiber Optical Sensor and Instrumentation for Gas Turbine Operation Condition Monitoring

    OpenAIRE

    Hua Xia; Doug Byrd; Sachin Dekate; Boon Lee

    2013-01-01

    Gas turbine operation control is normally based on thermocouple-measured exhaust temperatures. Due to radiation shielding and bulky package, it is difficult to provide high spatial resolution for measuring can-to-can combustion temperature profile at the exhaust duct. This paper has demonstrated that wavelength-division-multiplexing-based fiber Bragg grating sensors could provide high spatial resolution steady and dynamic temperature measurements. A robust sensor package can be designed with ...

  12. Highly sensitive and selective chemiresistor gas/vapor sensors based on polyaniline nanocomposite: A comprehensive review

    OpenAIRE

    Pandey, Sadanand

    2016-01-01

    This review article directs particular attention to some current breakthrough developments in the area of gas sensors based on polyaniline (PANI) nanocomposite. Conducting polymers symbolize a paramount class of organic materials that boost the resistivity towards external stimuli. Nevertheless, PANI-based sensor experiences some disadvantages of relatively low reproducibility, selectivity, and stability. In order to overcome these restrictions, PANI was functionalised or incorporated with na...

  13. Photonic Crystal Fiber-Based High Sensitivity Gas Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Los Gatos Research, Inc. proposes to develop a lightweight, compact, rugged, near-infrared gas-sensing spectroscopy instrument to accurately measure the abundance of...

  14. Photonic Crystal Fiber-Based High Sensitivity Gas Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Los Gatos Research, Inc. proposes to develop a lightweight, compact, rugged, near and mid-infrared gas-sensing spectroscopy instrument to accurately measure the...

  15. Bismuth-Based, Disposable Sensor for the Detection of Hydrogen Sulfide Gas.

    Science.gov (United States)

    Rosolina, Samuel M; Carpenter, Thomas S; Xue, Zi-Ling

    2016-02-02

    A new sensor for the detection of hydrogen sulfide (H2S) gas has been developed to replace commercial lead(II) acetate-based test papers. The new sensor is a wet, porous, paper-like substrate coated with Bi(OH)3 or its alkaline derivatives at pH 11. In contrast to the neurotoxic lead(II) acetate, bismuth is used due to its nontoxic properties, as Bi(III) has been a reagent in medications such as Pepto-Bismol. The reaction between H2S gas and the current sensor produces a visible color change from white to yellow/brown, and the sensor responds to ≥ 30 ppb H2S in a total volume of 1.35 L of gas, a typical volume of human breath. The alkaline, wet coating helps the trapping of acidic H2S gas and its reaction with Bi(III) species, forming colored Bi2S3. The sensor is suitable for testing human bad breath and is at least 2 orders of magnitude more sensitive than a commercial H2S test paper based on Pb(II)(acetate)2. The small volume of 1.35-L H2S is important, as the commercial Pb(II)(acetate)2-based paper requires large volumes of 5 ppm H2S gas. The new sensor reported here is inexpensive, disposable, safe, and user-friendly. A simple, laboratory setup for generating small volumes of ppb-ppm of H2S gas is also reported.

  16. Simulations, fabrication and characterization of diamond coated Love wave-type SAW sensors

    Czech Academy of Sciences Publication Activity Database

    Talbi, A.; Soltani, A.; Rumeau, A.; Taylor, Andrew; Drbohlavová, L.; Klimša, Ladislav; Kopeček, Jaromír; Fekete, Ladislav; Krečmarová, Marie; Mortet, Vincent

    2015-01-01

    Roč. 212, č. 11 (2015), 2606-2610 ISSN 1862-6300 R&D Projects: GA MŠk LO1409; GA MŠk(CZ) LM2011029; GA ČR GA13-31783S Institutional support: RVO:68378271 Keywords : acoustic sensors * chemical vapor deposition * diamond * nanocrystalline materials * quartz * surface acoustic waves Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.648, year: 2015

  17. Microfabricated gas sensor systems with sensitive nanocrystalline metal-oxide films

    Science.gov (United States)

    Graf, M.; Gurlo, A.; Bârsan, N.; Weimar, U.; Hierlemann, A.

    2006-12-01

    This article gives an overview on recent developments in metal-oxide-based gas sensor systems, in particular on nanocrystalline oxide materials deposited on modern, state-of-the-art sensor platforms fabricated in microtechnology. First, metal-oxide-based gas sensors are introduced, and the underlying principles and fundamentals of the gas sensing process are laid out. In the second part, the different deposition methods, such as evaporation, sputtering, sol-gel techniques, aerosol methods, and screen-printing, and their applicability to micro-scale substrates are discussed in terms of their deposition precision, the achievable layer thickness, as well as with regard to the possibility to use pre-processed materials. In the third part, microsensor platforms and, in particular, semiconductor- and microelectronics-based sensor platforms, which have been fabricated in, e.g., standard CMOS-technology (CMOS: complementary metal-oxide semiconductor), are briefly reviewed. The use of such microfabricated sensor platforms inevitably imposes constraints, such as temperature limits, on the applied nanomaterial processing and deposition methods. These limitations are discussed and work-arounds are described. Additionally, monolithic sensor systems are presented that combine microtransducers or microhotplates, which are coated with nanomaterials, with the necessary control and driving electronics on a single chip. The most advanced of such systems are standalone units that can be directly connected to a computer via a digital interface.

  18. Highly sensitive room temperature ammonia gas sensor based on Ir-doped Pt porous ceramic electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wenlong [College of pharmacy and biological engineering, Chengdu University, Chengdu, 610106 (China); Department of chemical and materials engineering, National Chin-Yi University of Technology, Taichung 411, Taiwan (China); Liu, Yen-Yu [Department of chemical and materials engineering, Tunghai University, Taichung 407, Taiwan (China); Do, Jing-Shan, E-mail: jsdo@ncut.edu.tw [Department of chemical and materials engineering, National Chin-Yi University of Technology, Taichung 411, Taiwan (China); Li, Jing, E-mail: lijing@cdu.edu.cn [College of pharmacy and biological engineering, Chengdu University, Chengdu, 610106 (China)

    2016-12-30

    Highlights: • Water vapors seem to hugely improve the electrochemical activity of the Pt and Pt-Ir porous ceramic electrodes. • The gas sensors based on the Pt and Pt-Ir alloy electrodes possess good sensing performances. • The reaction path of the ammonia on platinum has been discussed. - Abstract: Room temperature NH{sub 3} gas sensors based on Pt and Pt-Ir (Ir doping Pt) porous ceramic electrodes have been fabricated by both electroplating and sputtering methods. The properties of the gaseous ammonia sensors have been examined by polarization and chronoamperometry techniques. The influence of humidity on the features of the resulting sensors in the system has also been discussed, and the working potential was optimized. Water vapors seem to hugely improve the electrochemical activity of the electrode. With increasing the relative humidity, the response of the Pt-Ir(E)/Pt(S)/PCP sensor to NH{sub 3} gas could be enhanced remarkably, and the sensitivity increases from 1.14 to 12.06 μA ppm{sup −1} cm{sup −2} .Then we have also discussed the sensing mechanism of the Pt-Ir sensor and the result has been confirmed by X-ray photoelectron spectroscopy of the electrode surface before and after reaction in the end.

  19. Planar Indium Tin Oxide Heater for Improved Thermal Distribution for Metal Oxide Micromachined Gas Sensors

    Directory of Open Access Journals (Sweden)

    M. Cihan Çakır

    2016-09-01

    Full Text Available Metal oxide gas sensors with integrated micro-hotplate structures are widely used in the industry and they are still being investigated and developed. Metal oxide gas sensors have the advantage of being sensitive to a wide range of organic and inorganic volatile compounds, although they lack selectivity. To introduce selectivity, the operating temperature of a single sensor is swept, and the measurements are fed to a discriminating algorithm. The efficiency of those data processing methods strongly depends on temperature uniformity across the active area of the sensor. To achieve this, hot plate structures with complex resistor geometries have been designed and additional heat-spreading structures have been introduced. In this work we designed and fabricated a metal oxide gas sensor integrated with a simple square planar indium tin oxide (ITO heating element, by using conventional micromachining and thin-film deposition techniques. Power consumption–dependent surface temperature measurements were performed. A 420 °C working temperature was achieved at 120 mW power consumption. Temperature distribution uniformity was measured and a 17 °C difference between the hottest and the coldest points of the sensor at an operating temperature of 290 °C was achieved. Transient heat-up and cool-down cycle durations are measured as 40 ms and 20 ms, respectively.

  20. Highly sensitive and selective chemiresistor gas/vapor sensors based on polyaniline nanocomposite: A comprehensive review

    Directory of Open Access Journals (Sweden)

    Sadanand Pandey

    2016-12-01

    Full Text Available This review article directs particular attention to some current breakthrough developments in the area of gas sensors based on polyaniline (PANI nanocomposite. Conducting polymers symbolize a paramount class of organic materials that boost the resistivity towards external stimuli. Nevertheless, PANI-based sensor experiences some disadvantages of relatively low reproducibility, selectivity, and stability. In order to overcome these restrictions, PANI was functionalised or incorporated with nanoparticles (NPs (metallic or bimetallic NPs, metal oxide NPs, carbon compounds (like CNT or graphene, chalcogenides, polymers, showing improved gas sensing characteristics. It has been suggested that host–guest chemistry combined with the utilization of organic and inorganic analog in nanocomposite may allow for improvement of the sensor performance due to synergetic/complementary effects. Herein, we summarize recent advantages in PANI nanocomposite preparation, sensor construction, and sensing properties of various PANI nanocomposite-based gas/vapor sensors, such as NH3, H2, HCl, NO2, H2S, CO, CO2, SO2, LPG, vapor of volatile organic compounds (VOCs as well as chemical warfare agents (CWAs. The sensing mechanisms are discussed. Existing problems that may hinder practical applications of the sensors are also discussed.

  1. Enhancement of NH3 Gas Sensitivity at Room Temperature by Carbon Nanotube-Based Sensor Coated with Co Nanoparticles

    Directory of Open Access Journals (Sweden)

    Lich Quang Nguyen

    2013-01-01

    Full Text Available Multi-walled carbon nanotube (MWCNT film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH3 gas sensing applications. The MWCNT-based sensor is sensitive to NH3 gas at room temperature. Nanoclusters of Co catalysts have been sputtered on the surface of the MWCNT film to enhance gas sensitivity with respect to unfunctionalized CNT films. The gas sensitivity of Co-functionalized MWCNT-based gas sensors is thus significantly improved. The sensor exhibits good repeatability and high selectivity towards NH3, compared with alcohol and LPG.

  2. Enhancement of NH3 gas sensitivity at room temperature by carbon nanotube-based sensor coated with Co nanoparticles.

    Science.gov (United States)

    Nguyen, Lich Quang; Phan, Pho Quoc; Duong, Huyen Ngoc; Nguyen, Chien Duc; Nguyen, Lam Huu

    2013-01-30

    Multi-walled carbon nanotube (MWCNT) film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH(3) gas sensing applications. The MWCNT-based sensor is sensitive to NH(3) gas at room temperature. Nanoclusters of Co catalysts have been sputtered on the surface of the MWCNT film to enhance gas sensitivity with respect to unfunctionalized CNT films. The gas sensitivity of Co-functionalized MWCNT-based gas sensors is thus significantly improved. The sensor exhibits good repeatability and high selectivity towards NH(3), compared with alcohol and LPG.

  3. Gas Sensors Based on One Dimensional Nanostructured Metal-Oxides: A Review

    Directory of Open Access Journals (Sweden)

    A. S. M. A. Haseeb

    2012-05-01

    Full Text Available Recently one dimensional (1-D nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed. Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO2, TiO2, In2O3, WOx, AgVO3, CdO, MoO3, CuO, TeO2 and Fe2O3. Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research.

  4. Studying the Effect of Deposition Conditions on the Performance and Reliability of MEMS Gas Sensors

    Directory of Open Access Journals (Sweden)

    Walied Moussa

    2007-03-01

    Full Text Available In this paper, the reliability of a micro-electro-mechanical system (MEMS-based gas sensor has been investigated using Three Dimensional (3D coupled multiphysics Finite Element (FE analysis. The coupled field analysis involved a two-way sequential electro- thermal fields coupling and a one-way sequential thermal-structural fields coupling. An automated substructuring code was developed to reduce the computational cost involved in simulating this complicated coupled multiphysics FE analysis by up to 76 percent. The substructured multiphysics model was then used to conduct a parametric study of the MEMS-based gas sensor performance in response to the variations expected in the thermal and mechanical characteristics of thin films layers composing the sensing MEMS device generated at various stages of the microfabrication process. Whenever possible, the appropriate deposition variables were correlated in the current work to the design parameters, with good accuracy, for optimum operation conditions of the gas sensor. This is used to establish a set of design rules, using linear and nonlinear empirical relations, which can be utilized in real-time at the design and development decision-making stages of similar gas sensors to enable the microfabrication of these sensors with reliable operation.

  5. Gas Sensors Based on One Dimensional Nanostructured Metal-Oxides: A Review

    Science.gov (United States)

    Arafat, M. M.; Dinan, B.; Akbar, Sheikh A.; Haseeb, A. S. M. A.

    2012-01-01

    Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed. Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO2, TiO2, In2O3, WOx, AgVO3, CdO, MoO3, CuO, TeO2 and Fe2O3. Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research. PMID:22969344

  6. Progress in the development of semiconducting metal oxide gas sensors: a review

    Science.gov (United States)

    Moseley, Patrick T.

    2017-08-01

    Since the first suggestion, during the 1950s, that high-surface-area metal oxides could be used as conductometric gas sensors enormous efforts have been made to enhance both the selectivity and the sensitivity of such devices, and to reduce their operational power requirements. This development has involved the exploration of response mechanisms, the selection of the most appropriate oxide compositions, the fabrication of two-phase ‘hetero-structures’, the addition of metallic catalyst particles and the optimisation of the manner in which the materials are presented to the gas—the structure and the nanostructure of the sensing elements. Far more of the scientific literature has been devoted to seeking such improvements in metal oxide gas sensors than has been directed at all other solid-state gas sensors together. Recent progress in the research and development of metal oxide gas sensor technology is surveyed in this invited review. The advances that have been made are quite spectacular and the results of individual pieces of work are drawn together here so that trends can be seen. Emerging features include: the significance of n-type/p-type switching, the enhancement of sensing performance of materials through the incorporation of secondary components and the advantages of interrogating sensors with alternating current rather than direct current.

  7. Blood pulse wave velocity and pressure sensing via fiber based and free space based optical sensors

    Science.gov (United States)

    Sirkis, Talia; Beiderman, Yevgeny; Agdarov, Sergey; Beiderman, Yafim; Zalevsky, Zeev

    2017-02-01

    Continuous noninvasive measurement of vital bio-signs, such as cardiopulmonary parameters, is an important tool in evaluation of the patient's physiological condition and health monitoring. On the demand of new enabling technologies, some works have been done in continuous monitoring of blood pressure and pulse wave velocity. In this paper, we introduce two techniques for non-contact sensing of vital bio signs. In the first approach the optical sensor is based on single mode in-fibers Mach-Zehnder interferometer (MZI) to detect heartbeat, respiration and pulse wave velocity (PWV). The introduced interferometer is based on a new implanted scheme. It replaces the conventional MZI realized by inserting of discontinuities in the fiber to break the total internal reflection and scatter/collect light. The proposed fiber sensor was successfully incorporated into shirt to produce smart clothing. The measurements obtained from the smart clothing could be obtained in comfortable manner and there is no need to have an initial calibration or a direct contact between the sensor and the skin of the tested individual. In the second concept we show a remote noncontact blood pulse wave velocity and pressure measurement based on tracking the temporal changes of reflected secondary speckle patterns produced in human skin when illuminated by a laser beams. In both concept experimental validation of the proposed schemes is shown and analyzed.

  8. Instantaneous and efficient surface wave excitation of a low pressure gas or gases

    Science.gov (United States)

    Levy, Donald J.; Berman, Samuel M.

    1988-01-01

    A system for instantaneously ionizing and continuously delivering energy in the form of surface waves to a low pressure gas or mixture of low pressure gases, comprising a source of rf energy, a discharge container, (such as a fluorescent lamp discharge tube), an rf shield, and a coupling device responsive to rf energy from the source to couple rf energy directly and efficiently to the gas or mixture of gases to ionize at least a portion of the gas or gases and to provide energy to the gas or gases in the form of surface waves. The majority of the rf power is transferred to the gas or gases near the inner surface of the discharge container to efficiently transfer rf energy as excitation energy for at least one of the gases. The most important use of the invention is to provide more efficient fluorescent and/or ultraviolet lamps.

  9. The linear variable differential transformer (LVDT) position sensor for gravitational wave interferometer low-frequency controls

    CERN Document Server

    Tariq, H; Vetrano, F; Wang Chen Yang; Bertolini, A; Calamai, G; DeSalvo, R; Gennai, A; Holloway, L E; Losurdo, G; Marka, S; Mazzoni, M; Paoletti, F; Passuello, D; Sannibale, V; Stanga, R

    2002-01-01

    Low-power, ultra-high-vacuum compatible, non-contacting position sensors with nanometer resolution and centimeter dynamic range have been developed, built and tested. They have been designed at Virgo as the sensors for low-frequency modal damping of Seismic Attenuation System chains in Gravitational Wave interferometers and sub-micron absolute mirror positioning. One type of these linear variable differential transformers (LVDTs) has been designed to be also insensitive to transversal displacement thus allowing 3D movement of the sensor head while still precisely reading its position along the sensitivity axis. A second LVDT geometry has been designed to measure the displacement of the vertical seismic attenuation filters from their nominal position. Unlike the commercial LVDTs, mostly based on magnetic cores, the LVDTs described here exert no force on the measured structure.

  10. Impact Wave Monitoring in Soil Using a Dynamic Fiber Sensor Based on Stimulated Brillouin Scattering

    Directory of Open Access Journals (Sweden)

    Qingsong Cui

    2015-04-01

    Full Text Available The impact wave response of soil due to a ball drop is monitored on a 30.5 cm by 30.5 cm square soil box using a fiber sensor with dynamic strain sensing capability. The experiments are conducted in real time using a simple one-laser one-modulator configuration with stimulated Brillouin scattering. The embedded BOTDA sensor grid successfully monitored the distribution and evolution of the inner strains of a sand bed during a mass impact on its surface. The measurement of the distributed dynamic strains was possible in several milliseconds and with 1 cm actual location resolution. This paper presents a time-domain signal analysis utilized for determining the dynamic strains in embedded fiber sensor. The results demonstrate the method to be a promising one for detection of subsurface vibration and movement in geotechnical Structure Health Monitoring (SHM.

  11. The linear variable differential transformer (LVDT) position sensor for gravitational wave interferometer low-frequency controls

    Energy Technology Data Exchange (ETDEWEB)

    Tariq, Hareem E-mail: htariq@ligo.caltech.edu; Takamori, Akiteru; Vetrano, Flavio; Wang Chenyang; Bertolini, Alessandro; Calamai, Giovanni; DeSalvo, Riccardo; Gennai, Alberto; Holloway, Lee; Losurdo, Giovanni; Marka, Szabolcs; Mazzoni, Massimo; Paoletti, Federico; Passuello, Diego; Sannibale, Virginio; Stanga, Ruggero

    2002-08-21

    Low-power, ultra-high-vacuum compatible, non-contacting position sensors with nanometer resolution and centimeter dynamic range have been developed, built and tested. They have been designed at Virgo as the sensors for low-frequency modal damping of Seismic Attenuation System chains in Gravitational Wave interferometers and sub-micron absolute mirror positioning. One type of these linear variable differential transformers (LVDTs) has been designed to be also insensitive to transversal displacement thus allowing 3D movement of the sensor head while still precisely reading its position along the sensitivity axis. A second LVDT geometry has been designed to measure the displacement of the vertical seismic attenuation filters from their nominal position. Unlike the commercial LVDTs, mostly based on magnetic cores, the LVDTs described here exert no force on the measured structure.

  12. Integration of thin film giant magnetoimpedance sensor and surface acoustic wave transponder

    KAUST Repository

    Li, Bodong

    2012-03-09

    Passive and remote sensing technology has many potential applications in implantable devices, automation, or structural monitoring. In this paper, a tri-layer thin film giant magnetoimpedance (GMI) sensor with the maximum sensitivity of 16%/Oe and GMI ratio of 44% was combined with a two-port surface acoustic wave(SAW) transponder on a common substrate using standard microfabrication technology resulting in a fully integrated sensor for passive and remote operation. The implementation of the two devices has been optimized by on-chip matching circuits. The measurement results clearly show a magnetic field response at the input port of the SAW transponder that reflects the impedance change of the GMI sensor.

  13. High resolution wireless body area network with statistically synchronized sensor data for tracking pulse wave velocity.

    Science.gov (United States)

    Li, Kejia; Warren, Steve

    2012-01-01

    Wireless body area networks (WBANs) will take on more diverse forms in terms of their sensor combinations and communication protocols as their presence is extended to a greater number of monitoring scenarios. This paper presents an application layer protocol that solves issues caused by sensor nodes that must compete for high speed, real-time communication with the receiver. Such applications emphasize the delivery of large amounts of raw data from different sensor nodes in a time-synchronized manner, rather than channels that experience intermittent operation. An example of tracking pulse wave velocity (PWV) is introduced in this paper, where high-precision PWVs are estimated with the help of timeline recovery and feature extraction processes in MATLAB.

  14. Apparatus for sensor failure detection and correction in a gas turbine engine control system

    Science.gov (United States)

    Spang, H. A., III; Wanger, R. P. (Inventor)

    1981-01-01

    A gas turbine engine control system maintains a selected level of engine performance despite the failure or abnormal operation of one or more engine parameter sensors. The control system employs a continuously updated engine model which simulates engine performance and generates signals representing real time estimates of the engine parameter sensor signals. The estimate signals are transmitted to a control computational unit which utilizes them in lieu of the actual engine parameter sensor signals to control the operation of the engine. The estimate signals are also compared with the corresponding actual engine parameter sensor signals and the resulting difference signals are utilized to update the engine model. If a particular difference signal exceeds specific tolerance limits, the difference signal is inhibited from updating the model and a sensor failure indication is provided to the engine operator.

  15. Study of development of disturbance waves in annular gas-liquid flow

    Science.gov (United States)

    Cherdantsev, Andrey V.; Cherdantsev, Mikhail V.; Isaenkov, Sergey V.; Markovich, Dmitriy M.

    2017-09-01

    Downstream development of disturbance waves properties in annular regime of gas - liquid flow was conducted in adiabatic air-water downwards flow in a vertical pipe with inner diameter of 11.7 mm. The measurements were conducted using brightness-based laser-induced fluorescence technique. Instantaneous distributions of local thickness of liquid film along one longitudinal section of the duct over the first 45 cm from the inlet were obtained with sampling frequency of 10 kHz. Based on these spatiotemporal plots, dependence of local average velocity of disturbance waves on downstream distance was obtained for a wide range of gas and liquid flow rates. Three main stages of flow development were identified: a stage prior to formation of disturbance waves, a stage of constant acceleration of disturbance waves and a stage of deceleration nearly compensating the initial acceleration. Transitions to both second and third stages occur closer to the inlet at higher gas velocities and lower liquid flow rates. The initial acceleration is defined by the effect of the gas shear; it grows in parabolic manner with superficial gas velocity and shows weak dependence on liquid flow rate. The deceleration is supposed to occur due to entrainment of liquid from disturbance waves.

  16. A ‘Violin-Mode’ shadow sensor for interferometric gravitational wave detectors

    Science.gov (United States)

    Lockerbie, N. A.; Tokmakov, K. V.

    2014-12-01

    This paper describes a system of four novel shadow detectors having, collectively, a displacement sensitivity of (69  ±  13) picometres (rms) / √Hz, at 500 Hz, over a measuring span of ±0.1 mm. The detectors were designed to monitor the vibrations of the 600 mm long, 400 μm diameter, silica suspension fibres of the mirrors for the Advanced LIGO (Laser Interferometer Gravitational wave Observatory) gravitational wave detectors, at the resonances of the so-called Violin Modes (VM). The VM detection system described here had a target sensitivity of 100 pm (rms)/ √Hz at 500 Hz, together with, ultimately, a required detection span of ±0.1 mm about the mean position of each fibre—in order to compensate for potential slow drift over time of fibre position, due to mechanical relaxation. The full sensor system, comprising emitters (sources of illumination) and shadow detectors, therefore met these specifications. Using these sensors, VM resonances having amplitudes of 1.2 nm (rms) were detected in the suspension fibres of an Advanced LIGO dummy test-mass. The VM bandwidth of the sensor, determined by its transimpedance amplifier, was 226 Hz-8.93 kHz at the -3 dB points. This paper focuses mainly on the detector side of the shadow sensors. The emitters are described in an accompanying paper.

  17. The evaluation of the wave-form analysis capability of a new strain-gauge intracranial pressure MicroSensor.

    Science.gov (United States)

    Piper, I R; Miller, J D

    1995-06-01

    Both laboratory and clinical trials have indicated the reliability of a new catheter-tip, strain-gauge intracranial pressure transducer. We report on the results of bench tests comparing the wave-form analysis capabilities of the new Codman intracranial pressure MicroSensor and a similar strain-gauge transducer. Good agreement was found between the two sensors with no significant nonlinearity or hysteresis over a measured pressure range from 0 to 100 mg Hg. Under "fluid-filled" conditions, the MicroSensor showed good reproduction of an arterial pressure wave form; when spectral analysis was used to analyze the two sensor types and break them down into harmonic components, no significant differences could be found for any of the first 10 amplitude and phase harmonics. If proven to stay robust after long-term clinical use, this sensor may be a useful alternative to the existing transducer systems for routinely monitoring the intracranial pressure and its wave form.

  18. Current Fluctuation Measurements of Amperometric Gas Sensors Constructed with Three Different Technology Procedures

    Directory of Open Access Journals (Sweden)

    Sedlak Petr

    2016-12-01

    Full Text Available Electrochemical amperometric gas sensors represent a well-established and versatile type of devices with unique features: good sensitivity and stability, short response/recovery times, and low power consumption. These sensors operate at room temperature, and therefore have been applied in monitoring air pollutants and detection of toxic and hazardous gases in a number of areas. Some drawbacks of classical electrochemical sensors are overcome by the solid polymer electrolyte (SPE based on ionic liquids. This work presents evaluation of an SPE-based amperometric sensor from the point of view of current fluctuations. The sensor is based on a novel three-electrode sensor platform with solid polymer electrolytes containing ionic liquid for detection of nitrogen dioxide − a highly toxic gas that is harmful to the environment and presenting a possible threat to human health even at low concentrations. The paper focuses on using noise measurement (electric current fluctuation measurement for evaluation of electrochemical sensors which were constructed by different fabrication processes: (i lift-off and drop-casting technology, (ii screen printing technology on a ceramic substrate and (iii screen printing on a flexible substrate.

  19. Understanding the low temperature electrical properties of nanocrystalline tin oxide for gas sensor applications

    Science.gov (United States)

    Drake, Christina Hartsell

    Nanocrystalline metal/metal oxide is an important class of transparent and electronic materials due to its potential use in many applications, including gas sensors. At the nanoscale, many of the phenomena observed that give nanocrystalline semiconducting oxide enhanced performance as a gas sensor material over other conventional engineering materials is still poorly understood. This study is aimed at understanding the low temperature electrical and chemical properties of nanocrystalline SnO2 that makes it suitable for room temperature gas detectors. Studies were carried out in order to understand how various synthesis methods affect the surfaces on the nano-oxides, interactions of a target gas (in this study hydrogen) with different surface species, and changes in the electrical properties as a function of dopants and grain size. A correlation between the surface reactions and the electrical response of doped nanocrystalline metal-oxide-semiconductors exposed to a reducing gas is established using Fourier Transform Infrared (FTIR) Spectroscopy attached to a specially built custom designed catalytic cell. First principle calculations of oxygen vacancy concentrations from absorbance spectra are presented. FTIR is used for effectively screening of these nanostructures for gas sensing applications. The effect of processing temperature on the microstructural evolution and on the electronic properties of nanocrystalline trivalent doped-SnO 2 is also presented. This study includes the effect of dopants (In and Ce) on the growth of nano-SnO2, as well as their effects on the electronic properties and gas sensor behavior of the nanomaterial at room temperature. Band bending affects are also investigated for this system and are related to enhanced low temperature gas sensing. The role and importance of oxygen vacancies in the electronic and chemical behavior of surface modified nanocrystalline SnO2 are explored in this study. A generalized explanation for the low temperature

  20. Optical multi-species gas monitoring sensor and system

    Science.gov (United States)

    Polzin, Kurt A. (Inventor); Korman, Valentin (Inventor)

    2012-01-01

    The system includes at least one light source generating light energy having a corresponding wavelength. The system's sensor is based on an optical interferometer that receives light energy from each light source. The interferometer includes a free-space optical path disposed in an environment of interest. The system's sensor includes an optical device disposed in the optical path that causes light energy of a first selected wavelength to continue traversing the optical path whereas light energy of at least one second selected wavelength is directed away from the optical path. The interferometer generates an interference between the light energy of the first selected wavelength so-traversing the optical path with the light energy at the corresponding wavelength incident on the optical interferometer. A first optical detector detects the interference. At least one second detector detects the light energy at the at least one second selected wavelength directed away from the optical path.

  1. Recent progress on gas sensor based on quantum cascade lasers and hollow fiber waveguides

    Science.gov (United States)

    Liu, Ningwu; Sun, Juan; Deng, Hao; Ding, Junya; Zhang, Lei; Li, Jingsong

    2017-02-01

    Mid-infrared laser spectroscopy provides an ideal platform for trace gas sensing applications. Despite this potential, early MIR sensing applications were limited due to the size of the involved optical components, e.g. light sources and sample cells. A potential solution to this demand is the integration of hollow fiber waveguide with novelty quantum cascade lasers.Recently QCLs had great improvements in power, efficiency and wavelength range, which made the miniaturized platforms for gas sensing maintaining or even enhancing the achievable sensitivity conceivable. So that the miniaturization of QCLs and HWGs can be evolved into a mini sensor, which may be tailored to a variety of real-time and in situ applications ranging from environmental monitoring to workplace safety surveillance. In this article, we introduce QCLs and HWGs, display the applications of HWG based on QCL gas sensing and discuss future strategies for hollow fiber coupled quantum cascade laser gas sensor technology.

  2. First-Order Acoustic Wave Equation Reverse Time Migration Based on the Dual-Sensor Seismic Acquisition System

    Science.gov (United States)

    You, Jiachun; Liu, Xuewei; Wu, Ru-Shan

    2017-03-01

    We analyze the mathematical requirements for conventional reverse time migration (RTM) and summarize their rationale. The known information provided by current acquisition system is inadequate for the second-order acoustic wave equations. Therefore, we introduce a dual-sensor seismic acquisition system into the coupled first-order acoustic wave equations. We propose a new dual-sensor reverse time migration called dual-sensor RTM, which includes two input variables, the pressure and vertical particle velocity data. We focus on the performance of dual-sensor RTM in estimating reflection coefficients compared with conventional RTM. Synthetic examples are used for the study of estimating coefficients of reflectors with both dual-sensor RTM and conventional RTM. The results indicate that dual-sensor RTM with two inputs calculates amplitude information more accurately and images structural positions of complex substructures, such as the Marmousi model, more clearly than that of conventional RTM. This shows that the dual-sensor RTM has better accuracy in backpropagation and carries more information in the directivity because of particle velocity injection. Through a simple point-shape model, we demonstrate that dual-sensor RTM decreases the effect of multi-pathing of propagating waves, which is helpful for focusing the energy. In addition, compared to conventional RTM, dual-sensor RTM does not cause extra memory costs. Dual-sensor RTM is, therefore, promising for the computation of multi-component seismic data.

  3. Gas exchange in the ice zone: the role of small waves and big animals

    Science.gov (United States)

    Loose, B.; Takahashi, A.; Bigdeli, A.

    2016-12-01

    The balance of air-sea gas exchange and net biological carbon fixation determine the transport and transformation of carbon dioxide and methane in the ocean. Air-sea gas exchange is mostly driven by upper ocean physics, but biology can also play a role. In the open ocean, gas exchange increases proportionate to the square of wind speed. When sea ice is present, this dependence breaks down in part because breaking waves and air bubble entrainment are damped out by interactions between sea ice and the wave field. At the same time, sea ice motions, formation, melt, and even sea ice-associated organisms can act to introduce turbulence and air bubbles into the upper ocean, thereby enhancing air-sea gas exchange. We take advantage of the knowledge advances of upper ocean physics including bubble dynamics to formulate a model for air-sea gas exchange in the sea ice zone. Here, we use the model to examine the role of small-scale waves and diving animals that trap air for insulation, including penguins, seals and polar bears. We compare these processes to existing parameterizations of wave and bubble dynamics in the open ocean, to observe how sea ice both mitigates and locally enhances air-sea gas transfer.

  4. Fabrication od a ZnO/ST-cut quartz based love wave viscosity sensor

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Tsung Tsong; Huang, Zhi Da; Chen, Yung Yu; Liu, Pei Ling [Institute of Applied Mechanics, National Taiwan University, Taipai (China)

    2006-05-15

    In this paper, we aim to propose a rugged and relatively inexpensive acoustic wave viscometer that is easy to use and to fabricate by the conventional semiconductor manufacturing processes. First, we fabricated five different Love wave acoustic devices based on ZnO/90 degree rotated ST-quartz layered structure and incorporated with Polydimethylsiloxane (PMDS) flow cell. This allows a tiny controlled amount of analyte to be confined solely upon the sensing area between the IDTs of our Love wave sensor, preventing unwanted electric interactions with IDTs. The PDMS liquid flow cell is fabricated by replica molding. Using a simple set of fixture, the flow cell can be clamped onto our Love wave sensor and a constant volume of analyte can be confined on the sensing surface. Finally, five glycerites with different viscosities were prepared for viscosity measurement. The measured results show that the frequency shifts are in good correlation with the known viscosities. We note that results of this study can further be implemented as an easy to use and inexpensive acoustic viscometer.

  5. Fabrication on a ZnO/ST-cut quartz based love wave viscosity sensor

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Tsung Tsong; Huang, Zhi Da; Chen, Yung Yu; Liu, Pei Ling [Institute of Applied Mechanics, National Taiwan University, Taipai (China)

    2006-05-15

    In this paper, we aim to propose a rugged and relatively inexpensive acoustic wave viscometer that is easy to use and to fabricate by the conventional semiconductor manufacturing processes. First, we fabricated five different Love wave acoustic devices based on ZnO/90 degree rotated ST-quartz layered structure and incorporated with Polydimethylsiloxane (PMDS) flow cell. This allows a tiny controlled amount of analyte to be confined solely upon the sensing area between the IDTs of our Love wave sensor, preventing unwanted electric interactions with IDTs. The PDMS liquid flow cell is fabricated by replica molding. Using a simple set of fixture, the flow cell can be clamped onto our Love wave sensor and a constant volume of analyte can be confined on the sensing surface. Finally, five glycerites with different viscosities were prepared for viscosity measurement. The measured results show that the frequency shifts are in good correlation with the known viscosities. We note that results of this study can further be implemented as an easy to use and inexpensive acoustic viscometer.

  6. On-Line Corrosion Monitoring of Plate Structures Based on Guided Wave Tomography Using Piezoelectric Sensors.

    Science.gov (United States)

    Rao, Jing; Ratassepp, Madis; Lisevych, Danylo; Hamzah Caffoor, Mahadhir; Fan, Zheng

    2017-12-12

    Corrosion is a major safety and economic concern to various industries. In this paper, a novel ultrasonic guided wave tomography (GWT) system based on self-designed piezoelectric sensors is presented for on-line corrosion monitoring of large plate-like structures. Accurate thickness reconstruction of corrosion damages is achieved by using the dispersive regimes of selected guided waves and a reconstruction algorithm based on full waveform inversion (FWI). The system makes use of an array of miniaturised piezoelectric transducers that are capable of exciting and receiving highly dispersive A0 Lamb wave mode at low frequencies. The scattering from transducer array has been found to have a small effect on the thickness reconstruction. The efficiency and the accuracy of the new system have been demonstrated through continuous forced corrosion experiments. The FWI reconstructed thicknesses show good agreement with analytical predictions obtained by Faraday's law and laser measurements, and more importantly, the thickness images closely resemble the actual corrosion sites.

  7. BN-C Hybrid Nanoribbons as Gas Sensors

    Science.gov (United States)

    Darvishi Gilan, Mahdi; Chegel, Raad

    2018-02-01

    The effects of carbon monoxide (CO) and ammonia (NH3) molecules adsorption on the various composites of boron nitride and graphene BN-C hybrid nanoribbons are investigated using the non-equilibrium Green's function (NEGF) technique based on density functional theory (DFT). The effects of adsorption with possible random configurations on the average of the density of states (DOS), transmission coefficient, and the current-voltage ( I- V) characteristics are calculated. The results indicate that, by embedding armchair graphene nanoribbon (AGNR) with boron nitride nanoribbon (BNNR), the various electronic properties can be observed after gas molecule adsorption. The electronic structure and gap of hybrids system is modified due to gas adsorption, and the systems act like the n-type semiconductor by NH3 molecule adsorption. The hybrid structures due to their tunable band gap are better candidates for gas detecting compared to the pristine BNNRs and AGNRs.

  8. Implementation of a quantum cascade laser-based gas sensor prototype for sub-ppmv H2S measurements in a petrochemical process gas stream.

    Science.gov (United States)

    Moser, Harald; Pölz, Walter; Waclawek, Johannes Paul; Ofner, Johannes; Lendl, Bernhard

    2017-01-01

    The implementation of a sensitive and selective as well as industrial fit gas sensor prototype based on wavelength modulation spectroscopy with second harmonic detection (2f-WMS) employing an 8-μm continuous-wave distributed feedback quantum cascade laser (CW-DFB-QCL) for monitoring hydrogen sulfide (H2S) at sub-ppm levels is reported. Regarding the applicability for analytical and industrial process purposes aimed at petrochemical environments, a synthetic methane (CH4) matrix of up to 1000 ppmv together with a varying H2S content was chosen as the model environment for the laboratory-based performance evaluation performed at TU Wien. A noise-equivalent absorption sensitivity (NEAS) for H2S targeting the absorption line at 1247.2 cm(-1) was found to be 8.419 × 10(-10) cm(-1) Hz(-1/2), and a limit of detection (LOD) of 150 ppbv H2S could be achieved. The sensor prototype was then deployed for on-site measurements at the petrochemical research hydrogenation platform of the industrial partner OMV AG. In order to meet the company's on-site safety regulations, the H2S sensor platform was installed in an industry rack and equipped with the required safety infrastructure for protected operation in hazardous and explosive environments. The work reports the suitability of the sensor prototype for simultaneous monitoring of H2S and CH4 content in the process streams of a research hydrodesulfurization (HDS) unit. Concentration readings were obtained every 15 s and revealed process dynamics not observed previously.

  9. Deterministic prediction of waves and wave induced vessel motions : Future telling by using nautical radar as a remote wave sensor

    NARCIS (Netherlands)

    Naaijen, P.

    2017-01-01

    With many operations at sea carried out by ships or or other
    floating vessels, risks are involved because of the waves and
    resulting motions of the ships. Examples are the landing of helicopters on ships, transferring crew from a ship to a wind turbine, or working on the deck of an anchor

  10. Study of Influencing Factors of Dynamic Measurements Based on SnO2 Gas Sensor

    Directory of Open Access Journals (Sweden)

    Jinhuai Liu

    2004-08-01

    Full Text Available Abstract: The gas-sensing behaviour based on a dynamic measurement method of a single SnO2 gas sensor was investigated by comparison with the static measurement. The influencing factors of nonlinear response such as modulation temperature, duty ratio, heating waveform (rectangular, sinusoidal, saw-tooth, pulse, etc. were also studied. Experimental data showed that temperature was the most essential factor because the changes of frequency and heating waveform could result in the changes of temperature essentially.

  11. Catalytic-Metal/PdO(sub x)/SiC Schottky-Diode Gas Sensors

    Science.gov (United States)

    Hunter, Gary W.; Xu, Jennifer C.; Lukco, Dorothy

    2006-01-01

    Miniaturized hydrogen- and hydrocarbon-gas sensors, heretofore often consisting of Schottky diodes based on catalytic metal in contact with SiC, can be improved by incorporating palladium oxide (PdOx, where 0 less than or equal to x less than or equal to 1) between the catalytic metal and the SiC. In prior such sensors in which the catalytic metal was the alloy PdCr, diffusion and the consequent formation of oxides and silicides of Pd and Cr during operation at high temperature were observed to cause loss of sensitivity. However, it was also observed that any PdOx layers that formed and remained at PdCr/SiC interfaces acted as barriers to diffusion, preventing further deterioration by preventing the subsequent formation of metal silicides. In the present improvement, the lesson learned from these observations is applied by placing PdOx at the catalytic metal/SiC interfaces in a controlled and uniform manner to form stable diffusion barriers that prevent formation of metal silicides. A major advantage of PdOx over other candidate diffusion-barrier materials is that PdOx is a highly stable oxide that can be incorporated into gas sensor structures by use of deposition techniques that are standard in the semiconductor industry. The PdOx layer can be used in a gas sensor structure for improved sensor stability, while maintaining sensitivity. For example, in proof-of-concept experiments, Pt/PdOx/SiC Schottky-diode gas sensors were fabricated and tested. The fabrication process included controlled sputter deposition of PdOx to a thickness of 50 Angstroms on a 400-m-thick SiC substrate, followed by deposition of Pt to a thickness of 450 Angstroms on the PdOx. The SiC substrate (400 microns in thickness) was patterned with photoresist and a Schottky-diode photomask. A lift-off process completed the definition of the Schottky-diode pattern. The sensors were tested by measuring changes in forward currents at a bias potential of 1 V during exposure to H2 in N2 at temperatures

  12. Effective Use of Molecular Recognition in Gas Sensing: Results from Acoustic Wave and In-Situ FTIR Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Bodenhofer, K,; Gopel, W.; Hierlemann, A.; Ricco, A.J.

    1998-12-09

    To probe directly the analyte/film interactions that characterize molecular recognition in gas sensors, we recorded changes to the in-situ surface vibrational spectra of specifically fictionalized surface acoustic wave (SAW) devices concurrently with analyte exposure and SAW measurement of the extent of sorption. Fourier-lmnsform infrared external- reflectance spectra (FTIR-ERS) were collected from operating 97-MH2 SAW delay lines during exposure to a range of analytes as they interacted with thin-film coatings previously shown to be selective: cyclodextrins for chiral recognition, Ni-camphorates for Lewis bases such as pyridine and organophosphonates, and phthalocyanines for aromatic compounds. In most cases where specific chemical interactions-metal coordination, "cage" compound inclusion, or z stacking-were expected, analyte dosing caused distinctive changes in the IR spectr~ together with anomalously large SAW sensor responses. In contrast, control experiments involving the physisorption of the same analytes by conventional organic polymers did not cause similar changes in the IR spectra, and the SAW responses were smaller. For a given conventional polymer, the partition coefficients (or SAW sensor signals) roughly followed the analyte fraction of saturation vapor pressure. These SAW/FTIR results support earlier conclusions derived from thickness-shear mode resonator data.

  13. Chemical etching of Tungsten thin films for high-temperature surface acoustic wave-based sensor devices

    Energy Technology Data Exchange (ETDEWEB)

    Spindler, M., E-mail: m.spindler@ifw-dresden.de [IFW Dresden, SAWLab Saxony, P.O. Box 270116, D-01171 Dresden (Germany); Herold, S.; Acker, J. [BTU Cottbus – Senftenberg, Faculty of Sciences, P.O. Box 101548, 01968 Senftenberg (Germany); Brachmann, E.; Oswald, S.; Menzel, S.; Rane, G. [IFW Dresden, SAWLab Saxony, P.O. Box 270116, D-01171 Dresden (Germany)

    2016-08-01

    Surface acoustic wave devices are widely used as wireless sensors in different application fields. Recent developments aimed to utilize those devices as temperature sensors even in the high temperature range (T > 300 °C) and in harsh environmental conditions. Therefore, conventional materials, which are used for the substrate and for the interdigital transducer finger electrodes such as multilayers or alloys based on Al or Cu have to be exchanged by materials, which fulfill some important criteria regarding temperature related effects. Electron beam evaporation as a standard fabrication method is not well applicable for depositing high temperature stable electrode materials because of their very high melting points. Magnetron sputtering is an alternative deposition process but is also not applicable for lift-off structuring without any further improvement of the structuring process. Due to a relatively high Ar gas pressure of about 10{sup −1} Pa, the sidewalls of the photoresist line structures are also covered by the metallization, which subsequently prevents a successful lift-off process. In this study, we investigate the chemical etching of thin tungsten films as an intermediate step between magnetron sputtering deposition of thin tungsten finger electrodes and the lift-off process to remove sidewall covering for a successful patterning process of interdigital transducers. - Highlights: • We fabricated Tungsten SAW Electrodes by magnetron sputtering technology. • An etching process removes sidewall covering of photoresist, which allows lift-off. • Tungsten etching rates based on a hydrogen peroxide solutions were determined.

  14. Detonation wave parameters in a variable cross section channel in gas mixture of methane with oxygen and nitrogen

    Directory of Open Access Journals (Sweden)

    G. Y. Bivol

    2014-01-01

    Full Text Available Propagation of the detonation wave in gas mixtures of methane with oxygen in a channel of variable cross section was studied experimentally. To conduct these investigations a special detonation combustion chamber comprising sections of various diameters has been designed. In the section of detonation wave formation a combustible mixture was ignited. After that, a flame front accelerated till the formation of detonation. At the exit from the combustion chamber there was an outlet conical section. In conducted experiments the toe-in angle was equal to 3 °. The combustion chamber was open-ended. So an initial pressure inside the combustion chamber prior to each experiment was equal to the atmospheric pressure. The initial temperature was ambient one of 300 K. As a diagnostics, piezoelectric sensors of pressure and photo diodes were used.Detonation initiation was accomplished by spark gap. For this pulse generator I-1 was used. Spark energy did not exceed 0.1 J and was much lower than the energy of the direct initiation of detonation.Deflagration-to-detonation transition was occurred. A composition of the mixtures was selected in such a way that the detonation cell width was several times smaller than the diameter of the channel. The mixture was composed by the partial pressures of methane, oxygen, and nitrogen and was kept in the 40 l tank within 24 hours under 5-8 atm. pressure. Возникновение де- тонации возникало вследствие перехода горения в детонацию.The aim of this study was to determine the parameters of a detonation wave in a channel of variable cross section in the methane-oxygen mixture. The influence of nitrogen impurities on the cell size and the speed and pressure of the detonation wave was investigated.The waves velocities and peak pressures at the front of the detonation wave were measured depending on composition, including the presence of nitrogen. The sizes of the

  15. Effects of electron beam irradiation on tin dioxide gas sensors

    Indian Academy of Sciences (India)

    WINTEC

    Abstract. In this paper, the effects of electron beam irradiation on the gas sensing performance of tin dioxide thin films toward H2 are studied. The tin dioxide thin films were prepared by ultrasonic spray pyrolysis. The results show that the sensitivity increased after electron beam irradiation. The electron beam irradiation.

  16. Fiber-optic exhaust-gas sensor based on the fluorescence characteristics of Cu containing zeolites

    Science.gov (United States)

    Remillard, Jeffrey

    2000-03-01

    A single catalyst in the exhaust system can reduce the concentration of toxic gases emitted by automobiles if the engine is operated close to the stoichiometric air-fuel ratio. This is accomplished through the use of an electrochemical oxygen sensor in the exhaust stream. Near the stoichiometric point, this sensor produces a step-function response when the exhaust gas transitions from an oxygen-poor to an oxygen-rich condition. This talk describes a different kind of sensor based on the use of copper-containing zeolites that produces a proportional output. Zeolites are a class of aluminosilicate materials that have an open 3D structure containing channels and cavities. The Al sites are negatively charged and are generally compensated by cations present during formation of the zeolite. Our experiments use a zeolite designated Cu-ZSM-5, which has the protons originally present in the ZSM-5 material replaced with cupric (Cu^+2) ions. Exposure of this zeolite to a reducing gas results in the conversion of some cupric ions to cuprous (Cu^+1) ions. Subsequent exposure of the zeolite to an oxidizing gas reverses this reaction. The use of this material as a gas sensor is based on the observation that cuprous ions produce a green fluorescent emission when exposed to blue light, whereas no fluorescence is observed from cupric ions. Monitoring the fluorescence of Cu-ZSM-5 placed in a gas stream can thus provide information on the gas's reductant-to-oxidant ratio. We present the results of high temperature in-situ fluorescence spectra, intensity, and reponse-time measurements performed on samples of Cu-ZSM-5 exposed to various O_2-reductant combinations and also discuss data obtained from a single-fiber prototype sensor fabricated using a sol-gel processing technique.(J.T. Remillard et al.), Appl. Opt. 38 5306 (1999).

  17. Design of Highly Selective Gas Sensors via Physicochemical Modification of Oxide Nanowires: Overview

    Directory of Open Access Journals (Sweden)

    Hyung-Sik Woo

    2016-09-01

    Full Text Available Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and thus have been applied in the field of gas sensors over the years. In particular, n-type NWs such as SnO2, ZnO, and In2O3 are widely studied because of their simple synthetic preparation and high gas response. However, due to their usually high responses to C2H5OH and NO2, the selective detection of other harmful and toxic gases using oxide NWs remains a challenging issue. Various strategies—such as doping/loading of noble metals, decorating/doping of catalytic metal oxides, and the formation of core–shell structures—have been explored to enhance gas selectivity and sensitivity, and are discussed herein. Additional methods such as the transformation of n-type into p-type NWs and the formation of catalyst-doped hierarchical structures by branch growth have also proven to be promising for the enhancement of gas selectivity. Accordingly, the physicochemical modification of oxide NWs via various methods provides new strategies to achieve the selective detection of a specific gas, and after further investigations, this approach could pave a new way in the field of NW-based semiconductor-type gas sensors.

  18. A surface acoustic wave passive and wireless sensor for magnetic fields, temperature, and humidity

    KAUST Repository

    Li, Bodong

    2015-01-01

    In this paper, we report an integrated single-chip surface acoustic wave sensor with the capability of measuring magnetic field, temperature, and humidity. The sensor is fabricated using a thermally sensitive LiNbO3 substrate, a humidity sensitive hydrogel coating, and a magnetic field sensitive impedance load. The sensor response to individually and simultaneously changing magnetic field, temperature and humidity is characterized by connecting a network analyzer directly to the sensor. Analytical models for each measurand are derived and used to compensate noise due to cross sensitivities. The results show that all three measurands can be monitored in parallel with sensitivities of 75 ppm/°C, 0.13 dB/%R.H. (at 50%R.H.), 0.18 dB/Oe and resolutions of 0.1 °C, 0.4%R.H., 1 Oe for temperature, humidity and magnetic field, respectively. A passive wireless measurement is also conducted on a current line using, which shows the sensors capability to measure both temperature and current signals simultaneously.

  19. Optical sensor for carbon dioxide gas determination, characterization and improvements.

    Science.gov (United States)

    Aguayo-López, M L; Capitán-Vallvey, L F; Fernández-Ramos, M D

    2014-08-01

    A study of different alternatives to improve the stability and lifetime of sensors for the determination of gaseous CO2 has been performed. It includes the characterization of different sensing membranes, a discussion of the results obtained and possibilities for the future. The solid sensor membrane for gaseous CO2 based on changes in the luminiscence of a luminophore immobilized on O2-insensitive film, concurrent with the displacement of a pH indicator, has some drawbacks, such as the loss of efficiency over time and the need to maintain the sensor in special atmospheric conditions. As a solution to these drawbacks, two alternatives were tested, the first alternative was replacing the newly proposed tetraoctyl ammonium hydroxide (TOAOH ) phase transfer agent with other basic agents that did not undergo a Hoffman degradation reaction, and the second alternative was the use of hydrophilic polymers that could retain water needed for CO2 sensing more efficiently. The different membranes tested indicated that the use of tetramethyl ammonium (TMAOH) instead of TOAOH as the phase transfer agent produced better results regarding stability and sensitivity. In addition, replacing the membrane polymer with hydrophilic polymers improved the sensing characteristics in terms of response time and stability over hydrophobic polymers. With a detection limit of 0.006%, the response time is 19s and the recovery time is 100s. The lifetime of the sensing membranes, which do not need to be held in any special atmosphere other than darkness, is longer than at least 300 days for membranes with TMAOH in hydrophilic polymer and 515 days for membranes with TMAOH in ethyl cellulose. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. An increase in gas sensitivity and recovery of an MWCNT-based gas sensor system in response to an electric field

    Science.gov (United States)

    Lee, Sei-Hyun; Im, Ji Sun; Kang, Seok Chang; Bae, Tae-Sung; In, Se Jin; Jeong, Euigyung; Lee, Young-Seak

    2010-09-01

    The application of an electric field was found to markedly increase the sensitivity of a gas sensor system. Multi-walled carbon nanotubes (MWCNTs) were used as a gas-sensing material in order to detect a target nitrogen monoxide (NO) gas. The response of the gas sensor was evaluated under both positive and negative electric fields at various applied voltages. The responsiveness of the gas sensor increased by a factor of 2.5 as a function of increasing positive electric fields because of the optimized electron acceptor-donor reaction between the NO gas and the MWCNTs. It was concluded that the applied electric field accelerated the electron transfer between the NO gas and the MWCNTs.

  1. Effect of Intense Sound Waves on a Stationary Gas Flame

    Science.gov (United States)

    Hahnemann, H; Ehret, L

    1950-01-01

    Intense sound waves with a resonant frequency of 5000 cycles per second were imposed on a stationary propane-air flame issuing from a nozzle. In addition to a slight increase of the flame velocity, a fundamental change both in the shape of the burning zone and in the flow pattern could be observed. An attempt is made to explain the origin of the variations in the flame configuration on the basis of transition at the nozzle from jet flow to potential flow.

  2. A gas sensor using a multi-walled carbon nanotube sheet to detect oxygen molecules.

    Science.gov (United States)

    Jung, Daewoong; Lee, Kyung H; Kim, Donghyun; Overzet, Lawrence J; Lee, Gil S

    2013-12-01

    A gas sensor using a multi-walled carbon nanotube (MWCNT) sheet, which can detect oxygen (O2) gas, is presented and its output characteristics are evaluated in this study. A simple, cost effective and novel fabrication technique is described compared to dispersing CNTs into a liquid or polymer. The sheets are spun from a MWCNT forest grown on a silicon substrate; its electrical resistance decreases linearly with O2 exposure. The MWCNT sheet has a large surface area and many individual MWCNT contact points; this leads to a linear sensitivity, a fast response time, repeatability, and stability. It is well known that the surface distribution and areal density of MWCNTs have a significantly affect on their sensing characteristics. The sensors fabricated using dispersed CNTs on a substrate, either with separated CNTs of low density or with overlapping CNTs of low resistance, reveal much lower sensitivities. The large surface area and uniform distribution of the gas sensor, however, allow for the higher interaction of the MWCNTs with the O2 molecules, increasing the sensor's characteristics. Moreover, the MWCNT sheet does not need purification or a complex transfer process to be used as a sensor, making it suitable for practical applications.

  3. A Sensor for Gas Detection Fabricated by a Circular Single-wall Carbon Nanotube

    Directory of Open Access Journals (Sweden)

    Lun-Wei Chang

    2008-04-01

    Full Text Available This work endeavors to describe a circular shape of carbon nanotubes (CNT performed by ultrasonic agitation and assisted by a surfactant implemented for gas detection. In a well-dispersed CNT solution, we observed that the thinner thickness and the larger diameter CNT rings were formed than those of our previous study. This fact can be elucidated more fully that the depletion contact energy is modulated by theoretical estimation with the corresponding tendency in our samples. The separated CNT ring possessed with negative charges in sodium dodecyl sulfate (SDS surfactant solution can be easily absorbed on the sliced surface. Through the e-beam lithography and the lift-off process, a CNT ring was exploited as a gas sensor to detect an extremely low concentration of methane gas. The circular CNT sensor has a prominent conduction response embodied in the existence of more defects in the ring CNT sensor than those of the straight CNT sensor. Moreover, the much fast response time in the circular CNT illustrates the demand of the shorter length of CNTs. The CNT ring features with longer persistent to current conduction after long time measurements appraising to be a robust and durable material in the sensor applications.

  4. Liquefied petroleum gas sensor based on manganese (III) oxide and zinc manganese (III) oxide nanoparticles

    Science.gov (United States)

    Sharma, Shiva; Chauhan, Pratima; Husain, Shahid

    2018-01-01

    In this paper, {{{Mn}}}2{{{O}}}3 and {{{ZnMn}}}2{{{O}}}4 nanoparticles (NPs) are successfully synthesized using chemical co-precipitation method at room temperature and further annealed at 450 °C. The structure, crystallite size, morphology, specific surface area (SSA) and band gap energy have been determined by x-ray diffraction, transmission electron microscopy, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy (SEM-EDS) and UV–visible spectrophotometer. The sensor films of the {{{Mn}}}2{{{O}}}3 NPs and {{{ZnMn}}}2{{{O}}}4 NPs have been fabricated onto glass substrate using spin coater system separately. These sensor films are investigated for different concentrations (200–1200 ppm) of liquefied petroleum gas (LPG) at different operating temperatures ranging from 100 °C to 400 °C. A comparative study of gas sensing properties shows that spinel {{{ZnMn}}}2{{{O}}}4 sensor film exhibit excellent response (≈ 80 % ) towards 1000 ppm LPG at 300 °C in comparison to {{{Mn}}}2{{{O}}}3 sensor films. The enhancement in the gas sensing characteristics of {{{ZnMn}}}2{{{O}}}4 sensor film is attributed to the reduced crystallite size, greater SSA, and modification in structure as well as morphology.

  5. Wave aberrations in a spinning pipe gas lens

    CSIR Research Space (South Africa)

    Mafusire, C

    2009-06-01

    Full Text Available The graded index (GRIN-like) medium generated by a gas inside a heated pipe when it is rotated about its longitudinal axis has the ability to focus a laser beam. However, recent research has shown that the medium generated has a deleterious effect...

  6. Fabrication of a SnO2-Based Acetone Gas Sensor Enhanced by Molecular Imprinting

    Directory of Open Access Journals (Sweden)

    Wenhu Tan

    2014-12-01

    Full Text Available This work presents a new route to design a highly sensitive SnO2–based sensor for acetone gas enhanced by the molecular imprinting technique. Unassisted and acetone-assisted thermal synthesis methods are used to synthesis SnO2 nanomaterials. The prepared SnO2 nanomaterials have been characterized by X-ray powder diffraction, scanning electron microscopy and N2 adsorption−desorption. Four types of SnO2 films were obtained by mixing pure deionized water and liquid acetone with the two types of as-prepared powders, respectively. The acetone gas sensing properties of sensors coated by these films were evaluated. Testing results reveal that the sensor coated by the film fabricated by mixing liquid acetone with the SnO2 nanomaterial synthesized by the acetone-assisted thermal method exhibits the best acetone gas sensing performance. The sensor is optimized for the smooth adsorption and desorption of acetone gas thanks to the participation of acetone both in the procedure of synthesis of the SnO2 nanomaterial and the device fabrication, which results in a distinct response–recovery behavior.

  7. Circuit and Noise Analysis of Odorant Gas Sensors in an E-Nose

    OpenAIRE

    Tian, Fengchun; Yang, Simon X.; Dong, Kevin

    2005-01-01

    In this paper, the relationship between typical circuit structures of gas sensor circuits and their output noise is analyzed. By using averaged segmenting periodical graph and improved histogram estimation methods, we estimated their noise power spectra and optimal probability distribution functions (pdf). The results were confirmed through experiment studies.

  8. Application of Gas Sensor Arrays in Assessment of Wastewater Purification Effects

    Directory of Open Access Journals (Sweden)

    Łukasz Guz

    2014-12-01

    Full Text Available A gas sensor array consisting of eight metal oxide semiconductor (MOS type gas sensors was evaluated for its ability for assessment of the selected wastewater parameters. Municipal wastewater was collected in a wastewater treatment plant (WWTP in a primary sedimentation tank and was treated in a laboratory-scale sequential batch reactor (SBR. A comparison of the gas sensor array (electronic nose response to the standard physical-chemical parameters of treated wastewater was performed. To analyze the measurement results, artificial neural networks were used. E-nose—gas sensors array and artificial neural networks proved to be a suitable method for the monitoring of treated wastewater quality. Neural networks used for data validation showed high correlation between the electronic nose readouts and: (I chemical oxygen demand (COD (r = 0.988; (II total suspended solids (TSS (r = 0.938; (III turbidity (r = 0.940; (IV pH (r = 0.554; (V nitrogen compounds: N-NO3 (r = 0.958, N-NO2 (r = 0.869 and N-NH3 (r = 0.978; (VI and volatile organic compounds (VOC (r = 0.987. Good correlation of the abovementioned parameters are observed under stable treatment conditions in a laboratory batch reactor.

  9. Temperature and Humidity Dependence of a Polymer-Based Gas Sensor

    Science.gov (United States)

    Ryan, M. A.; Buehler, M. G.

    1997-01-01

    This paper quantifies the temperature and humidity dependence of a polymer-based gas sensor. The measurement and analysis of three polymers indicates that resistance changes in the polymer films, due to temperature and humidity, can be positive or negative. The temperature sensitivity ranged from +1600 to -320 ppm/nd the relative sensitivity ranged from +1100 to -260 ppm/%.

  10. Low Temperature CVD Grown Graphene for Highly Selective Gas Sensors Working under Ambient Conditions

    NARCIS (Netherlands)

    Ricciardella, F.; Vollebregt, S.; Polichetti, T.; Alfano, B.; Massera, E.; Sarro, P.M.

    2017-01-01

    In this paper we report on gas sensors based on graphene grown by Chemical Vapor Deposition at 850 °C. Mo was used as catalyst for graphene nucleation. Resistors were directly designed on pre-patterned Mo using the transfer-free process we recently developed, thus avoiding films damage during the

  11. Thin film zinc oxide gas sensor fabricated using near-field electrospray

    National Research Council Canada - National Science Library

    Zheng, Gaofeng; Zhu, Ping; Sun, Lingling; Jiang, Jiaxin; Liu, Juan; Wang, Xiang; Li, Wenwang

    2016-01-01

    .... These particles were heated and oxidized to form a zinc oxide (ZnO) semiconductor at 500 °C. The resulting ZnO thin film on the comb electrode was incorporated into a gas sensor, which was examined using a custom built measurement system...

  12. Elaboration of ammonia gas sensors based on electrodeposited polypyrrole--cobalt phthalocyanine hybrid films.

    Science.gov (United States)

    Patois, Tilia; Sanchez, Jean-Baptiste; Berger, Franck; Fievet, Patrick; Segut, Olivier; Moutarlier, Virginie; Bouvet, Marcel; Lakard, Boris

    2013-12-15

    The electrochemical incorporation of a sulfonated cobalt phthalocyanine (sCoPc) in conducting polypyrrole (PPy) was done, in the presence or absence of LiClO4, in order to use the resulting hybrid material for the sensing of ammonia. After electrochemical deposition, the morphological features and structural properties of polypyrrole/phthalocyanine hybrid films were investigated and compared to those of polypyrrole films. A gas sensor consisting in platinum microelectrodes arrays was fabricated using silicon microtechnologies, and the polypyrrole and polypyrrole/phthalocyanine films were electrochemically deposited on the platinum microelectrodes arrays of this gas sensor. When exposed to ammonia, polymer-based gas sensors exhibited a decrease in conductance due to the electron exchange between ammonia and sensitive polymer-based layer. The characteristics of the gas sensors (response time, response amplitude, reversibility) were studied for ammonia concentrations varying from 1 ppm to 100 ppm. Polypyrrole/phthalocyanine films exhibited a high sensitivity and low detection limit to ammonia as well as a fast and reproducible response at room temperature. The response to ammonia exposition of polypyrrole films was found to be strongly enhanced thanks to the incorporation of the phthalocyanine in the polypyrrole matrix. © 2013 Elsevier B.V. All rights reserved.

  13. Modeling the sensing characteristics of chemi-resistive thin film semi-conducting gas sensors.

    Science.gov (United States)

    Ghosh, Abhishek; Majumder, S B

    2017-08-30

    For chemi-resistive thin film gas sensors a generic theoretical model is proposed to predict the variation of sensor response with the operating temperature and thickness of the sensing film. A diffusion equation is formulated assuming that inflammable target gases move through the sensing film by Knudsen diffusion and react with the adsorbed oxygen following first-order kinetics. We have assumed a realistic non-linear variation between the conductance and test gas concentration and derived a general expression relating the sensor response to the operating temperature and thickness of the film. Assuming Langmuir adsorption kinetics, we have theoretically predicted the response and recovery transients during gas sensing using thin film sensing elements. It is predicted that for irreversible type sensing, the response time is reduced with an increase in test gas concentration, whereas for reversible sensing, the response time is independent of test gas concentration. For zinc oxide thin film sensors, an excellent match is obtained between the model prediction and experimental data for their thickness (122 nm to 380 nm) and temperature variation (200 °C to 325 °C) in 500 ppm carbon monoxide (CO) sensing. The maximum CO response% (∼53%) was achieved in 320 nm thick ZnO films. The conductance transients for response and recovery for CO sensing closely follow Langmuir adsorption kinetics and as predicted theoretically, indeed for irreversible sensing, the response time reduces from 350 s to 220 s with an increase in test gas concentration from 20 to 550 ppm. In the case of reversible sensing we found that the response time is ∼55 s irrespective of the CO gas concentration in the range of 5-500 ppm. The models developed in the present work are quite generic in nature and we have discussed their applicability to a wide variety of sensing materials with various types of surface morphologies.

  14. NDIR Gas Sensor for Spatial Monitoring of Carbon Dioxide Concentrations in Naturally Ventilated Livestock Buildings.

    Science.gov (United States)

    Mendes, Luciano B; Ogink, Nico W M; Edouard, Nadège; van Dooren, Hendrik Jan C; Tinôco, Ilda de Fátima F; Mosquera, Julio

    2015-05-13

    The tracer gas ratio method, using CO2 as natural tracer, has been suggested as a pragmatic option to measure emissions from naturally ventilated (NV) barns without the need to directly estimate the ventilation rate. The aim of this research was to assess the performance of a low-cost Non-Dispersive Infra-Red (NDIR) sensor for intensive spatial field monitoring of CO2 concentrations in a NV dairy cow house. This was achieved by comparing NDIR sensors with two commonly applied methods, a Photo-Acoustic Spectroscope (PAS) Gas Monitor and an Open-Path laser (OP-laser). First, calibrations for the NDIR sensors were obtained in the laboratory. Then, the NDIR sensors were placed in a dairy cow barn for comparison with the PAS and OP-laser methods. The main conclusions were: (a) in order to represent the overall barn CO2 concentration of the dairy cow barn, the number of NDIR sensors to be accounted for average concentration calculation was dependent on barn length and on barn area occupation; and (b) the NDIR CO2 sensors are suitable for multi-point monitoring of CO2 concentrations in NV livestock barns, being a feasible alternative for the PAS and the OP-laser methods to monitor single-point or averaged spatial CO2 concentrations in livestock barns.

  15. NDIR Gas Sensor for Spatial Monitoring of Carbon Dioxide Concentrations in Naturally Ventilated Livestock Buildings

    Directory of Open Access Journals (Sweden)

    Luciano B. Mendes

    2015-05-01

    Full Text Available The tracer gas ratio method, using CO2 as natural tracer, has been suggested as a pragmatic option to measure emissions from naturally ventilated (NV barns without the need to directly estimate the ventilation rate. The aim of this research was to assess the performance of a low-cost Non-Dispersive Infra-Red (NDIR sensor for intensive spatial field monitoring of CO2 concentrations in a NV dairy cow house. This was achieved by comparing NDIR sensors with two commonly applied methods, a Photo-Acoustic Spectroscope (PAS Gas Monitor and an Open-Path laser (OP-laser. First, calibrations for the NDIR sensors were obtained in the laboratory. Then, the NDIR sensors were placed in a dairy cow barn for comparison with the PAS and OP-laser methods. The main conclusions were: (a in order to represent the overall barn CO2 concentration of the dairy cow barn, the number of NDIR sensors to be accounted for average concentration calculation was dependent on barn length and on barn area occupation; and (b the NDIR CO2 sensors are suitable for multi-point monitoring of CO2 concentrations in NV livestock barns, being a feasible alternative for the PAS and the OP-laser methods to monitor single-point or averaged spatial CO2 concentrations in livestock barns.

  16. Highly Sensitive and Selective Gas Sensor Using Hydrophilic and Hydrophobic Graphenes

    Science.gov (United States)

    Some, Surajit; Xu, Yang; Kim, Youngmin; Yoon, Yeoheung; Qin, Hongyi; Kulkarni, Atul; Kim, Taesung; Lee, Hyoyoung

    2013-06-01

    New hydrophilic 2D graphene oxide (GO) nanosheets with various oxygen functional groups were employed to maintain high sensitivity in highly unfavorable environments (extremely high humidity, strong acidic or basic). Novel one-headed polymer optical fiber sensor arrays using hydrophilic GO and hydrophobic reduced graphene oxide (rGO) were carefully designed, leading to the selective sensing of volatile organic gases for the first time. The two physically different surfaces of GO and rGO could provide the sensing ability to distinguish between tetrahydrofuran (THF) and dichloromethane (MC), respectively, which is the most challenging issue in the area of gas sensors. The eco-friendly physical properties of GO allowed for faster sensing and higher sensitivity when compared to previous results for rGO even under extreme environments of over 90% humidity, making it the best choice for an environmentally friendly gas sensor.

  17. Membrane-Coated Electrochemical Sensor for Corrosion Monitoring in Natural Gas Pipelines

    Directory of Open Access Journals (Sweden)

    J. Beck

    2017-07-01

    Full Text Available Electrochemical sensors can be used for a wide range of online in- situ process monitoring applications. However, the lack of a consistent electrolyte layer has previously limited electrochemical monitoring in gas and supercritical fluid streams. A solid state sensor is being designed that uses an ion conducting membrane to perform conductivity and corrosion measurements in natural gas pipelines up to 1000 psi. Initial results show that membrane conductivity measurements can be correlated directly to water content down to dew points of 1°C with good linearity. Corrosion monitoring can also be performed using methods such as linear polarization resistance and electrochemical impedance spectroscopy (EIS, though care must be taken in the electrode design to minimize deviation between sensors.

  18. Automatic carbon dioxide-methane gas sensor based on the solubility of gases in water.

    Science.gov (United States)

    Cadena-Pereda, Raúl O; Rivera-Muñoz, Eric M; Herrera-Ruiz, Gilberto; Gomez-Melendez, Domingo J; Anaya-Rivera, Ely K

    2012-01-01

    Biogas methane content is a relevant variable in anaerobic digestion processing where knowledge of process kinetics or an early indicator of digester failure is needed. The contribution of this work is the development of a novel, simple and low cost automatic carbon dioxide-methane gas sensor based on the solubility of gases in water as the precursor of a sensor for biogas quality monitoring. The device described in this work was used for determining the composition of binary mixtures, such as carbon dioxide-methane, in the range of 0-100%. The design and implementation of a digital signal processor and control system into a low-cost Field Programmable Gate Array (FPGA) platform has permitted the successful application of data acquisition, data distribution and digital data processing, making the construction of a standalone carbon dioxide-methane gas sensor possible.

  19. Automatic Carbon Dioxide-Methane Gas Sensor Based on the Solubility of Gases in Water

    Directory of Open Access Journals (Sweden)

    Raúl O. Cadena-Pereda

    2012-08-01

    Full Text Available Biogas methane content is a relevant variable in anaerobic digestion processing where knowledge of process kinetics or an early indicator of digester failure is needed. The contribution of this work is the development of a novel, simple and low cost automatic carbon dioxide-methane gas sensor based on the solubility of gases in water as the precursor of a sensor for biogas quality monitoring. The device described in this work was used for determining the composition of binary mixtures, such as carbon dioxide-methane, in the range of 0–100%. The design and implementation of a digital signal processor and control system into a low-cost Field Programmable Gate Array (FPGA platform has permitted the successful application of data acquisition, data distribution and digital data processing, making the construction of a standalone carbon dioxide-methane gas sensor possible.

  20. Thermal balance analysis of a micro-thermoelectric gas sensor using catalytic combustion of hydrogen.

    Science.gov (United States)

    Nagai, Daisuke; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

    2014-01-21

    A thermoelectric gas sensor (TGS) with a combustion catalyst is a calorimetric sensor that changes the small heat of catalytic combustion into a signal voltage. We analyzed the thermal balance of a TGS to quantitatively estimate the sensor parameters. The voltage signal of a TGS was simulated, and the heat balance was calculated at two sections across the thermoelectric film of a TGS. The thermal resistances in the two sections were estimated from the thermal time constants of the experimental signal curves of the TGS. The catalytic combustion heat Q(catalyst) required for 1 mV of ∆V(gas) was calculated to be 46.1 μW. Using these parameters, we find from simulations for the device performance that the expected Q(catalyst) for 200 and 1,000 ppm H₂ was 3.69 μW and 11.7 μW, respectively.

  1. Real-Time Gas Identification by Analyzing the Transient Response of Capillary-Attached Conductive Gas Sensor

    Directory of Open Access Journals (Sweden)

    Behzad Bahraminejad

    2010-05-01

    Full Text Available In this study, the ability of the Capillary-attached conductive gas sensor (CGS in real-time gas identification was investigated. The structure of the prototype fabricated CGS is presented. Portions were selected from the beginning of the CGS transient response including the first 11 samples to the first 100 samples. Different feature extraction and classification methods were applied on the selected portions. Validation of methods was evaluated to study the ability of an early portion of the CGS transient response in target gas (TG identification. Experimental results proved that applying extracted features from an early part of the CGS transient response along with a classifier can distinguish short-chain alcohols from each other perfectly. Decreasing time of exposition in the interaction between target gas and sensing element improved the reliability of the sensor. Classification rate was also improved and time of identification was decreased. Moreover, the results indicated the optimum interval of the early transient response of the CGS for selecting portions to achieve the best classification rates.

  2. NO x gas detection characteristics in FET-type multi-walled carbon nanotube-based gas sensors for various electrode spacings

    Science.gov (United States)

    Kim, Hyun Soo; Jang, Kyung Uk; Kim, Tae Wan

    2016-03-01

    In this study, we fabricated a p-channel FET-type NO x gas sensor by using multi-walled carbon nanotubes (MWCNTs). Carbon nanotubes (CNTs) have good electronic, chemical-stability, and sensitivity characteristics. In particular, gas sensors require characteristics such as high speed, selectivity, and sensitivity. The fabricated sensor was used to detect NO x gas for different values of the gate-source voltage (V gs ) and the electrode spacings (30, 60, 90, and 120 μm). The gas sensor that absorbed NO x gas molecules showed a decrease in resistance. The sensitivity of the gas sensor was increased by increasing the electrode spacing. Additionally, while changing the Vgs and the temperature inside the chamber for the MWCNT gas sensor, we obtained the sensitivity and the normalized response for detecting NO x gas. We also obtained the adsorption energy (U a ) by using Arrhenius plots based on the reduction of resistance due to voltage variations. The adsorption energy was found to increase with increasing applied voltage.

  3. Novel Self-Heated Gas Sensors Using on-Chip Networked Nanowires with Ultralow Power Consumption.

    Science.gov (United States)

    Tan, Ha Minh; Manh Hung, Chu; Ngoc, Trinh Minh; Nguyen, Hugo; Duc Hoa, Nguyen; Van Duy, Nguyen; Hieu, Nguyen Van

    2017-02-22

    The length of single crystalline nanowires (NWs) offers a perfect pathway for electron transfer, while the small diameter of the NWs hampers thermal losses to tje environment, substrate, and metal electrodes. Therefore, Joule self-heating effect is nearly ideal for operating NW gas sensors at ultralow power consumption, without additional heaters. The realization of the self-heated NW sensors using the "pick and place" approach is complex, hardly reproducible, low yield, and not applicable for mass production. Here, we present the sensing capability of the self-heated networked SnO2 NWs effectively prepared by on-chip growth. Our developed self-heated sensors exhibit a good response of 25.6 to 2.5 ppm NO2 gas, while the response to 500 ppm H2, 100 ppm NH3, 100 ppm H2S, and 500 ppm C2H5OH is very low, indicating the good selectivity of the sensors to NO2 gas. Furthermore, the detection limit is very low, down to 82 parts-per-trillion. As-obtained sensing performance under self-heating mode is nearly identical to that under external heating mode. While the power consumption under self-heating mode is extremely low, around hundreds of microwatts, as scaled-down the size of the electrode is below 10 μm. The selectivity of the sensors can be controlled simply by tuning the loading power that enables simple detection of NO2 in mixed gases. Remarkable performance together with a significantly facile fabrication process of the present sensors enhances the potential application of NW sensors in next generation technologies such as electronic noses, the Internet of Things, and smartphone sensing.

  4. Enhanced Sensitivity of Surface Acoustic Wave-Based Rate Sensors Incorporating Metallic Dot Arrays

    Directory of Open Access Journals (Sweden)

    Wen Wang

    2014-02-01

    Full Text Available A new surface acoustic wave (SAW-based rate sensor pattern incorporating metallic dot arrays was developed in this paper. Two parallel SAW delay lines with a reverse direction and an operation frequency of 80 MHz on a same X-112°Y LiTaO3 wafer are fabricated as the feedback of two SAW oscillators, and mixed oscillation frequency was used to characterize the external rotation. To enhance the Coriolis force effect acting on the SAW propagation, a copper (Cu dot array was deposited along the SAW propagation path of the SAW devices. The approach of partial-wave analysis in layered media was referred to analyze the response mechanisms of the SAW based rate sensor, resulting in determination of the optimal design parameters. To improve the frequency stability of the oscillator, the single phase unidirectional transducers (SPUDTs and combed transducer were used to form the SAW device to minimize the insertion loss and accomplish the single mode selection, respectively. Excellent long-term (measured in hours frequency stability of 0.1 ppm/h was obtained. Using the rate table with high precision, the performance of the developed SAW rate sensor was evaluated experimentally; satisfactory detection sensitivity (16.7 Hz∙deg∙s−1 and good linearity were observed.

  5. LINC-NIRVANA Pathfinder: testing the next generation of wave front sensors at LBT

    Science.gov (United States)

    Conrad, Albert R.; Arcidiacono, Carmelo; Baumeister, Harald; Bergomi, Maria; Bertram, Thomas; Berwein, Juergen; Biddick, Chris; Bizenberger, Peter; Brangier, Matthieu; Briegel, Florian; Brunelli, Alessandro; Brynnel, Joar; Busoni, Lorenzo; Cushing, Norm; De Bonis, Fulvio; De La Pena, Michele; Esposito, Simone; Farinato, Jacopo; Fini, Luca; Green, Richard F.; Herbst, Tom; Hofferbert, Ralph; Kittmann, Frank; Kuerster, Martin; Laun, Werner; Meschke, Daniel; Mohr, Lars; Pavlov, Aleksei; Pott, Jorg-Uwe; Puglisi, Alfio; Ragazzoni, Roberto; Rakich, Andrew; Rohloff, Ralf-Rainer; Trowitzsch, Jan; Viotto, Valentina; Zhang, Xianyu

    2012-07-01

    LINC-NIRVANA will employ four wave front sensors to realize multi-conjugate correction on both arms of a Fizeau interferometer for LBT. Of these, one of the two ground-layer wave front sensors, together with its infrared test camera, comprise a stand-alone test platform for LINC-NIRVANA. Pathfinder is a testbed for full LINC-NIRVANA intended to identify potential interface problems early in the game, thus reducing both technical, and schedule, risk. Pathfinder will combine light from multiple guide stars, with a pyramid sensor dedicated to each star, to achieve ground-layer AO correction via an adaptive secondary: the 672-actuator thin shell at the LBT. The ability to achieve sky coverage by optically coadding light from multiple stars has been previously demonstrated; and the ability to achieve correction with an adaptive secondary has also been previously demonstrated. Pathfinder will be the first system at LBT to combine both of these capabilities. Since reporting our progress at A04ELT2, we have advanced the project in three key areas: definition of specific goals for Pathfinder tests at LBT, more detail in the software design and planning, and calibration. We report on our progress and future plans in these three areas, and on the project overall.

  6. Gas selectivity control in Co3O4 sensor via concurrent tuning of gas reforming and gas filtering using nano-scale hetero-overlayer of catalytic oxides.

    Science.gov (United States)

    Jeong, Hyun-Mook; Jeong, Seong-Yong; Kim, Jae-Hyeok; Kim, Bo-Young; Kim, Jun-Sik; Abdel-Hady, Faissal; Wazzan, Abdulaziz A; Al-Turaif, Hamad Ali; Jang, Ho Won; Lee, Jong-Heun

    2017-11-07

    Co3O4 sensors with a nanoscale TiO2 or SnO2 catalytic overlayer were prepared by screen printing of Co3O4 yolk-shell spheres and subsequent e-beam evaporation of TiO2 and SnO2. The Co3O4 sensors with 5 nm thick TiO2 and SnO2 overlayers showed high responses (resistance ratios) to 5 ppm xylene (14.5 and 28.8) and toluene (11.7 and 16.2) at 250°C with negligible responses to interference gases such as ethanol, HCHO, CO, and benzene. In contrast, the pure Co3O4 sensor did not show remarkable selectivity toward any specific gas. The response and selectivity to methylbenzenes and ethanol could be systematically controlled by selecting the catalytic overlayer material, varying the overlayer thickness, and tuning the sensing temperature. The significant enhancement of the selectivity for xylene and toluene was attributed to the reforming of less reactive methylbenzenes into more reactive and smaller species and oxidative filtering of other interference gases, including ubiquitous ethanol. The concurrent control of the gas reforming and oxidative filtering processes using a nano-scale overlayer of catalytic oxides provides a new, general, and powerful tool for designing highly selective and sensitive oxide semiconductor gas sensors.

  7. ALAT PENDETEKSI KEBOCORAN GAS BERACUN CO PADA MOBIL DENGAN ARRAY SENSOR MENGGUNAKAN FUZZY CONTROLLER

    Directory of Open Access Journals (Sweden)

    Slamet Widodo

    2016-03-01

    Full Text Available Perkembangan teknologi otomotif sekarang ini semakin pesat yaitu dengan fasilitas accessories mobil yang semakin lengkap. Namun berbagai fasilitas yang terdapat dalam mobil tanpa disadari menyimpan ancaman bahaya bagi pengguna mobil salah satunya ketika system pada AC (Air Conditioner terjadi kebocoran maka gas CO (karbon monoksida akan memenuhi ruang mobil yang tertutup. Gas CO ini sangat berbahaya karena gas ini tidak berwarna, tidak berbau, dan tidak berasa sehingga sulit untuk dideteksi yang dapat menyebabkan orang yang ada didalam mobil menjadi mati lemas tanpa disadari karena menghirup gas CO yang bocor. Dengan fenomena tersebut dibutuhkan sebuah alat yang dapat mendeteksi dan mengontrol kebocoran gas CO untuk memberikan rasa aman kepada pengguna mobil. Alat ini menggunakan kendali logika fuzzy sebagai proses pengambilan keputusan sebagai hasil nilai dari inferensi kerja array sensor. Pengendali utama pada sistem menggunakan mikrokontroller ATmega32. Ketika array sensor yaitu TGS2442 dan TGS2600 mendeteksi kadar gas CO >29,0 ppm berarti dalam status bahaya sehingga buzzer akan aktif diikuti motor DC yang menggerakkan kaca mobil agar terbuka. Berdasarkan lima kali pengujian yang dilakukan didapatkanlah rata-rata selisih error output gas sebesar 0.29 ppm disaat kondisi aman dan 3.87 ppm disaat kondisi bahaya.

  8. ALAT PENDETEKSI KEBOCORAN GAS BERACUN CO PADA MOBIL DENGAN ARRAY SENSOR MENGGUNAKAN FUZZY CONTROLLER

    Directory of Open Access Journals (Sweden)

    Slamet Widodo

    2016-09-01

    Full Text Available Perkembangan teknologi otomotif sekarang ini semakin pesat yaitu dengan fasilitas accessories mobil yang semakin lengkap. Namun berbagai fasilitas yang terdapat dalam mobil tanpa disadari menyimpan ancaman bahaya bagi pengguna mobil salah satunya ketika system pada AC (Air Conditioner terjadi kebocoran maka gas CO (karbon monoksida akan memenuhi ruang mobil yang tertutup. Gas CO ini sangat berbahaya karena gas ini tidak berwarna, tidak berbau, dan tidak berasa sehingga sulit untuk dideteksi yang dapat menyebabkan orang yang ada didalam mobil menjadi mati lemas tanpa disadari karena menghirup gas CO yang bocor. Dengan fenomena tersebut dibutuhkan sebuah alat yang dapat mendeteksi dan mengontrol kebocoran gas CO untuk memberikan rasa aman kepada pengguna mobil. Alat ini menggunakan kendali logika fuzzy sebagai proses pengambilan keputusan sebagai hasil nilai dari inferensi kerja array sensor. Pengendali utama pada sistem menggunakan mikrokontroller ATmega32. Ketika array sensor yaitu TGS2442 dan TGS2600 mendeteksi kadar gas CO >29,0 ppm berarti dalam status bahaya sehingga buzzer akan aktif diikuti motor DC yang menggerakkan kaca mobil agar terbuka. Berdasarkan lima kali pengujian yang dilakukan didapatkanlah rata-rata selisih error output gas sebesar 0.29 ppm disaat kondisi aman dan 3.87 ppm disaat kondisi bahaya.

  9. Gas Sensor Based on 3-D WO3 Inverse Opal: Design and Applications

    Science.gov (United States)

    Xing, Ruiqing; Du, Yang; Zhao, Xiaonan; Zhang, Xiu

    2017-01-01

    A three-dimensional inverse opal (3DIO) WO3 architecture has been synthesized via a simple sacrificial template method. Morphology features of the 3DIO were characterized by scanning electron microscope (SEM) and its structure was characterized by X-ray diffraction (XRD). The shrinking ratio of the PMMA spheres was ~28.2% through measuring the distribution of the PMMA spheres and 3DIO WO3 center-to-center distance between the spheres and macropores, respectively. Beyond that, the 3DIO gas sensing properties were investigated systematically and the sensing mechanism of 3DIO WO3 was proposed. The results indicated that the response of the 3DIO sensor possessed excellent sensitivity to acetone gas, especially at trace levels. The 3DIO gas sensor response was ~7 to 5 ppm of acetone and could detect acetone low to 0.2 ppm effectively, which was in close proximity to the theoretical low detection limit of 0.14 ppm when Ra/Rg ≥ 1.2 was used as the criterion for reliable gas sensing. All in all, the obvious satisfaction of the gas-sensing properties was ascribed to the structure of the 3DIO, and the sensor could be a promising novel device in the future. PMID:28353672

  10. Gas Sensor Based on 3-D WO3 Inverse Opal: Design and Applications

    Directory of Open Access Journals (Sweden)

    Ruiqing Xing

    2017-03-01

    Full Text Available A three-dimensional inverse opal (3DIO WO3 architecture has been synthesized via a simple sacrificial template method. Morphology features of the 3DIO were characterized by scanning electron microscope (SEM and its structure was characterized by X-ray diffraction (XRD. The shrinking ratio of the PMMA spheres was ~28.2% through measuring the distribution of the PMMA spheres and 3DIO WO3 center-to-center distance between the spheres and macropores, respectively. Beyond that, the 3DIO gas sensing properties were investigated systematically and the sensing mechanism of 3DIO WO3 was proposed. The results indicated that the response of the 3DIO sensor possessed excellent sensitivity to acetone gas, especially at trace levels. The 3DIO gas sensor response was ~7 to 5 ppm of acetone and could detect acetone low to 0.2 ppm effectively, which was in close proximity to the theoretical low detection limit of 0.14 ppm when Ra/Rg ≥ 1.2 was used as the criterion for reliable gas sensing. All in all, the obvious satisfaction of the gas-sensing properties was ascribed to the structure of the 3DIO, and the sensor could be a promising novel device in the future.

  11. Development of MWCNTs/alumina composite-based sensor for trace level ammonia gas sensing

    Science.gov (United States)

    Sharma, Sakshi; Hussain, Shahir; Sengupta, K.; Islam, S. S.

    2013-06-01

    Multi-walled carbon nanotube (MWCNT)/alumina (Al2O3) composite thin film-based low cost, rigid and highly efficient sensors were developed for trace level ammonia (NH3) gas sensing applications. Composite films were prepared by dispersing MWCNTs in varying concentration in alumina solution following the sol-gel process. The sensor response as a function MWCNT concentrations were measured and compared. The notable characteristics of these sensors are fast response time (10 minutes), and excellent reproducibility with detection level up to 6 ppm. Although poor NH3 desorption causes a high recovery time, fast and complete recovery was acquired using appropriate thermal treatment protocol. The sensitivity was found to be proportional to NH3 concentrations in the range 6-25 ppm and then gradually saturated at higher concentrations. However, a decrease in the sensor response was observed with increase in concentrations of MWCNTs.

  12. Deodorant Characteristics of Breath Odor Occurred from Favorite Foods Using Metal Oxide Gas Sensors

    Science.gov (United States)

    Seto, Shuichi; Oyabu, Takashi; Cai, Kuiqian; Katsube, Teruaki

    Three types of metal oxide gas sensors were adopted to detect the degree of breath odor. Various sorts of information are included in the odor. Each sensor has different sensitivities to gaseous chemical substances and the sensitivities also differ according to human behaviors, for example taking a meal, teeth-brushing and drinking something. There is also a possibility that the sensor can detect degrees of daily fatigue. Sensor sensitivities were low for the expiration of the elderly when the subject drank green tea. In this study, it is thought that the odor system can be incorporated into a healing robot. The robot can communicate with the elderly using several words and also connect to Internet. As for the results, the robot can identify basic human behaviors and recognize the living conditions of the resident. Moreover, it can also execute a kind of information retrieval through the Internet. Therefore, it has healing capability for the aged, and can also receive and transmit information.

  13. Highly sensitive gas leak detector based on a quartz-enhanced photoacoustic SF6 sensor.

    Science.gov (United States)

    Sampaolo, Angelo; Patimisco, Pietro; Giglio, Marilena; Chieco, Leonardo; Scamarcio, Gaetano; Tittel, Frank K; Spagnolo, Vincenzo

    2016-07-11

    The implementation, performance validation, and testing of a gas-leak optical sensor based on mid-IR quartz-enhanced photoacoustic (QEPAS) spectroscopic technique is reported. A QEPAS sensor was integrated in a vacuum-sealed test station for mechatronic components. The laser source for the sensor is a quantum cascade laser emitting at 10.56 µm, resonant with a strong absorption band of sulfur hexafluoride (SF6), which was selected as a leak tracer. The minimum detectable concentration of the QEPAS sensor is 2.7 parts per billion with an integration time of 1 s, corresponding to a sensitivity of leak flows in the 10-9 mbar∙l/s range, comparable with state-of-the-art leak detection techniques.

  14. A simple microfluidic chlorine gas sensor based on gas-liquid chemiluminescence of luminol-chlorine system.

    Science.gov (United States)

    Gao, Zhao-Xin; Li, Hai-Fang; Liu, Jiangjiang; Lin, Jin-Ming

    2008-08-01

    In this work, a microfluidic chlorine gas sensor based on gas-liquid interface absorption and chemiluminescence detection was described. The liquid chemiluminescence reagent-alkaline luminol solution can be stably sandwiched between two convex halves of a microchannel by surface tension. When chlorine gas was introduced into the micro device, it was dissolved into the interfacial luminol solution and transferred to ClO(-), and simultaneously luminol was excited and chemiluminescence emitted. The emitted chemiluminescence light was perpendicularly detected by a photomultiplier tube on a certain detection region. The remarkable advantage of the detection system is that both adsorption and detection were carried out at the gas-liquid interface, which avoids the appearance of bubbles. The whole analytical cycle including filling CL reagent, sample injection, CL detection and emptying the device was as short as 30 s. The linear concentration range of chlorine gas detection with direct introduction of sample method is from 0.5 to 478 ppm. The detection limit of this method is 0.2 ppm for standard chlorine gas and the relative standard deviation of five determinations of 3.19 ppm spiked chlorine sample was 5.2%.

  15. Research on sensor technology of Lamb-wave signal acquisition using optical low-coherence

    Science.gov (United States)

    Zhu, Y. K.; Yang, C.; Li, X. W.; Chong, B.

    2012-10-01

    Non-destructive testing of composite materials is a key technology issue in equipment testing. Among the emerging new testing methods, Lamb-wave technology is getting more and more attention. This paper proposed a sensing method to acquire the Lamb-wave signal in thin plate based on optical low-coherence principles. Methods to acquire Lamb-wave in thin plate using optical low-coherence technology were analyzed, and the technical path of non-contact, high-precision method was chosen. Complete in-line experimental system and methods were designed and built up for testing. A sensor system based on Michelson low-coherence interferometer was set up. The distributed optical fiber sensors were arranged on the top of sample materials for signal detection. Mirrors to enhance reflection intensity were attached on the sample. The phase of sensing arm was modulated by PZT vibration. Then signals were detected and processed by Daubechies10 wavelet and Gabor wavelet. In-line testing of thin plate with features of high-precision and high signal-noise-ratio was realized, which is meaningful to dynamic testing of large-scale structure.

  16. 40 A Platinum-porous SiC gas sensor: Investigation sensing properties of H{sub 2} gas

    Energy Technology Data Exchange (ETDEWEB)

    Keffous, A., E-mail: keffousa@yahoo.fr [Centre de Recherche en Technologie des Semiconducteurs pourl' energetique (CRTSE), 02Bd, Frantz Fanon, B.P. 140, Algiers (Algeria); Cheriet, A.; Hadjersi, T.; Boukennous, Y.; Gabouze, N.; Boukezzata, A.; Belkacem, Y. [Centre de Recherche en Technologie des Semiconducteurs pourl' energetique (CRTSE), 02Bd, Frantz Fanon, B.P. 140, Algiers (Algeria); Kechouane, M. [Houari Boumediene University (USTHB), Physical Faculty (Algeria); Kerdja, T. [Advanced Technology Center (CDTA) (Algeria); Menari, H.; Berouaken, M.; Talbi, L.; Ouadah, Y. [Centre de Recherche en Technologie des Semiconducteurs pourl' energetique (CRTSE), 02Bd, Frantz Fanon, B.P. 140, Algiers (Algeria)

    2013-01-01

    The present paper reports on a new structure for H{sub 2} gas sensing based on thin porous silicon carbide (PSiC) films. The PSiC layer has been formed by electrochemical etching of SiC films previously deposited onto p-type silicon substrate by pulsed laser deposition (PLD) using 6H-SiC target. Current-voltage (I-V) and current-time (I-t) characteristics have been measured. A thin platinum (Pt) film (40 A thickness) deposited onto PSiC layer has been used as a catalytic metal. The Schottky diode parameters such as ideality factor (n), barrier height ({phi}{sub Bp}) and series resistance (R{sub S}) have been evaluated under different concentrations of H{sub 2} gas. The experimental results show that upon exposure to H{sub 2} gas the barrier height, the ideality factor and the series resistance change significantly. The different changes in the electrical parameters of the structure (increase and decrease as a function of the H{sub 2} concentration) have been explained by the formation of two inversion layers. The first one forms as soon as the gas is in contact with the sensor and the second when the concentration reaches 90 ppm. Subsequently, the effect of gas concentration on the maximum sensitivity value of the sensor has been investigated. A high sensitivity ({Delta}I/I) value around 86% is found at about 1 V bias voltage. In addition, the response and recovery times were determined to be around 55 s and 160 s, respectively. Finally, the structure shows a reversible response for low gas concentration at room temperature.

  17. Effect of electrode gap on the sensing properties of multiwalled carbon nanotubes based gas sensor

    Science.gov (United States)

    Saheed, Mohamed Shuaib Mohamed; Mohamed, Norani Muti; Burhanudin, Zainal Arif

    2016-11-01

    Vertically aligned multiwalled carbon nanotubes (MWCNT) were grown on Si substrate coated with alumina and iron using chemical vapor deposition. Electrode gap of 10, 25 and 50 µm were adopted to determine the effect of varying gap spacing on the sensing properties such as voltage breakdown, sensitivity and selectivity for three gases namely argon, carbon dioxide and ammonia. Argon has the lowest voltage breakdown for every electrode gap. The fabricated MWCNT based gas sensor drastically reduced the voltage breakdown by 89.5% when the electrode spacing is reduced from 50 µm to 10 µm. The reduction is attributed to the high non-uniform electric field between the electrodes caused by the protrusion of nanotips. The sensor shows good sensitivity and selectivity with the ability to detect the gas in the mixture with air provided that the concentration is ≥ 20% where the voltage breakdown will be close to the pure gas.

  18. Transfer of CVD-grown graphene for room temperature gas sensors

    Science.gov (United States)

    Rigoni, F.; Maiti, R.; Baratto, C.; Donarelli, M.; MacLeod, J.; Gupta, B.; Lyu, M.; Ponzoni, A.; Sberveglieri, G.; Motta, N.; Faglia, G.

    2017-10-01

    An easy transfer procedure to obtain graphene-based gas sensing devices operating at room temperature (RT) is presented. Starting from chemical vapor deposition-grown graphene on copper foil, we obtained single layer graphene which could be transferred onto arbitrary substrates. In particular, we placed single layer graphene on top of a SiO2/Si substrate with pre-patterned Pt electrodes to realize a chemiresistor gas sensor able to operate at RT. The responses to ammonia (10, 20, 30 ppm) and nitrogen dioxide (1, 2, 3 ppm) are shown at different values of relative humidity, in dark and under 254 nm UV light. In order to check the sensor selectivity, gas response has also been tested towards hydrogen, ethanol, acetone and carbon oxide. Finally, a model based on linear dispersion relation characteristic of graphene, which take into account humidity and UV light effects, has been proposed.

  19. Preparation of Copper Oxide Nanostructure Thin Film For Carbon Monoxide Gas Sensor

    Directory of Open Access Journals (Sweden)

    Brian Yuliarto

    2016-11-01

    Full Text Available This work reports the synthesis of nanostructure of CuO thin film using dip coating and chemical bath deposition method. Seed layer was deposited by dip coating method using zinc nitrate as a precursor. The CuO nanostructure has successfully grown on CBD process at 95oC for 6 hours. The X Ray Diffraction characterization result shows that the CuO has monoclinic crystallization and good crystallinity. Moreover, the Scanning Electron Microscope characterization results  shows that CuO has nanospike-like shape. The CuO thin film as a gas sensor shows relatively high response on CO gas at the temperature working above 200oC. The highest response is obtained at 350oC of working temperature toward 30 ppm CO gas at 186% of sensor response.

  20. Global Coverage Measurement Planning Strategies for Mobile Robots Equipped with a Remote Gas Sensor

    Directory of Open Access Journals (Sweden)

    Muhammad Asif Arain

    2015-03-01

    Full Text Available The problem of gas detection is relevant to many real-world applications, such as leak detection in industrial settings and landfill monitoring. In this paper, we address the problem of gas detection in large areas with a mobile robotic platform equipped with a remote gas sensor. We propose an algorithm that leverages a novel method based on convex relaxation for quickly solving sensor placement problems, and for generating an efficient exploration plan for the robot. To demonstrate the applicability of our method to real-world environments, we performed a large number of experimental trials, both on randomly generated maps and on the map of a real environment. Our approach proves to be highly efficient in terms of computational requirements and to provide nearly-optimal solutions.

  1. Infrared semiconductor laser based trace gas sensor technologies: recent advances and applications

    Science.gov (United States)

    Tittel, Frank K.; Curl, Robert F.; Dong, Lei; Lewicki, Rafal

    2011-05-01

    Recent advances in the development of trace gas sensors based on the use of quantum cascade lasers (QCLs) for the sensitive, selective detection, quantification and monitoring of small molecular gas species with resolved spectroscopic features will be described. High detection sensitivity at ppbv and sub-ppbv concentration levels require detection sensitivity, enhancement schemes such as multipass absorption cells, cavity enhanced absorption techniques, or quartz enhanced photo-acoustic absorption spectroscopy (QEPAS). These three spectroscopic methods can achieve minimum detectable absorption losses in the range from 10-8 to 10-11 cm-1/√Hz. Two recent examples of real world applications of field deployable PAS and QEPAS based gas sensors will be reported, namely the monitoring of ammonia concentrations in exhaled human breath and major urban environments.

  2. Dióxido de estanho nanoestruturado como sensor de NOx Nanostructured tin dioxide as a NOx gas sensor

    Directory of Open Access Journals (Sweden)

    A. P. Maciel

    2003-09-01

    Full Text Available Neste trabalho, nanopartículas de SnO2 foram obtidas pelo método do precursor polimérico e caracterizadas por difração de raios X, isotermas de adsorção-dessorção, microscopia eletrônica de varredura e microscopia eletrônica de transmissão. Apenas a fase cassiterita (tetragonal foi observada. O material obtido apresenta com alta área superficial e porosidade. Estas características são pré-requisitos para um bom sensor de gás. A sensibilidade ao NOx para o SnO2 foi estudado na faixa de temperatura compreendida entre 200 e 500 ºC. Observou-se uma baixa sensibilidade entre 200 e 350 ºC, porém, a partir de 400 ºC ocorreu um aumento de três vezes na sensibilidade do sensor. A máxima sensibilidade ocorreu em 400 ºC, com um tempo de resposta de 730 s.In this work SnO2 nanoparticles were obtained by the polimeric precursor method and characterized by X-ray diffraction, gas adsorption and desorption isotherms, scanning electron microscopy and transmission electron microscopy. Only the cassiterite (tetragonal phase was observed. The obtained material presents a high surface area and high porosity. These characteristics are prerequisites for a good gas sensor. The NOx sensibility was studied in the temperature range between 200 and 500 °C. A low sensibility between 200 to 350 °C is also observed; however, starting from 400 °C, an increase of three times in the sensor sensibility occurs. The maximum sensibility was measured at 400 °C with a response time of 730 s.

  3. Possibility of gas sensor based on C{sub 20} molecular devices

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Wenkai [School of Physics and Optoelectronics Engineering, Ludong University, Yantai 264025 (China); Yang, Chuanlu, E-mail: yangchuanlu@126.com [School of Physics and Optoelectronics Engineering, Ludong University, Yantai 264025 (China); Zou, Dongqing [School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Sun, Zhaopeng [School of Physics and Optoelectronics Engineering, Ludong University, Yantai 264025 (China); Ji, Guomin [Electrical and Computer Engineering, The University of Oklahoma, Norman, Tulsa, OK 74078 (United States)

    2017-06-09

    We theoretically investigate the possibility of diatomic gas detection (NO, CO, O{sub 2}) by making use of the transport properties of the C{sub 20} molecular junctions. The calculations are performed by using nonequilibrium Green's function (NEGF) formalism in combination with density functional theory (DFT). In this work, we systematically study the most stable adsorption structural configurations, adsorption energy, and the transport properties on C{sub 20} molecular junctions with these diatomic gas molecules. It is found that NO and O{sub 2} gas molecule can be detected selectively. We suggest its possibility of nanosensors for highly sensitive and selective based on C{sub 20} molecular junction systems. - Highlights: • The most favorable adsorption site is investigated. • The mechanism of gas sensors is revealed. • NO and O{sub 2} gas molecules can be detected by C{sub 20} selectively.

  4. Understanding the fundamental principles of metal oxide based gas sensors; the example of CO sensing with SnO sub 2 sensors in the presence of humidity

    CERN Document Server

    Barsan, N

    2003-01-01

    This paper investigates the effect of water vapour in CO sensing by using Pd doped SnO sub 2 sensors realized in thick film technology as an example of the basic understanding of sensing mechanisms applied to sensors. The results of phenomenological and spectroscopic measurement techniques, all of them obtained under working conditions for sensors, were combined with modelling in order to derive conclusions able to be generalized to the field of metal oxide based gas sensors. The techniques employed were: dc conductance, ac impedance spectroscopy, work function (by using the Kelvin probe method), catalytic conversion and diffuse reflectance infrared Fourier transform measurements. The most important conclusion is that the different parts of the sensor (sensing layer, electrodes, substrate) are all influencing the gas detection and their role has to be taken into consideration when one attempts to understand how a sensor works. (topical review)

  5. Preparation and characterization of ALD deposited ZnO thin films studied for gas sensors

    Energy Technology Data Exchange (ETDEWEB)

    Boyadjiev, S.I., E-mail: boiajiev@gmail.com [MTA-BME Technical Analytical Chemistry Research Group, Szent Gellért tér 4, Budapest, H-1111 (Hungary); Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia (Bulgaria); Georgieva, V. [Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia (Bulgaria); Yordanov, R. [Department of Microelectronics, Technical University of Sofia, 8 Kliment Ohridski Blvd., 1756 Sofia (Bulgaria); Raicheva, Z. [Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia (Bulgaria); Szilágyi, I.M. [MTA-BME Technical Analytical Chemistry Research Group, Szent Gellért tér 4, Budapest, H-1111 (Hungary); Budapest University of Technology and Economics, Department of Inorganic and Analytical Chemistry, Szent Gellért tér 4, Budapest, H-1111 (Hungary)

    2016-11-30

    Highlights: • For the first time the gas sensing towards NO{sub 2} of very thin ALD ZnO films is studied. • The very thin ALD ZnO films showed excellent sensitivity to NO{sub 2} at room temperature. • These very thin film ZnO-based QCM sensors very well register even low concentrations. • The sensors have fully reversible sorption and are able to be recovered in short time. • Described fast and cost-effective ALD deposition of ZnO thin films for QCM gas sensor. - Abstract: Applying atomic layer deposition (ALD), very thin zinc oxide (ZnO) films were deposited on quartz resonators, and their gas sensing properties were studied using the quartz crystal microbalance (QCM) method. The gas sensing of the ZnO films to NO{sub 2} was tested in the concentration interval between 10 and 5000 ppm. On the basis of registered frequency change of the QCM, for each concentration the sorbed mass was calculated. Further characterization of the films was carried out by various techniques, i.e. by SEM-EDS, XRD, ellipsometry, and FTIR spectroscopy. Although being very thin, the films were gas sensitive to NO{sub 2} already at room temperature and could register very well as low concentrations as 100 ppm, while the sorption was fully reversible. Our results for very thin ALD ZnO films show that the described fast, simple and cost-effective technology could be implemented for producing gas sensors working at room temperature and being capable to detect in real time low concentrations of NO{sub 2}.

  6. MWCNT-polymer composites as highly sensitive and selective room temperature gas sensors

    Science.gov (United States)

    Mangu, Raghu; Rajaputra, Suresh; Singh, Vijay P.

    2011-05-01

    Multi-walled carbon nanotubes (MWCNTs)-polymer composite-based hybrid sensors were fabricated and integrated into a resistive sensor design for gas sensing applications. Thin films of MWCNTs were grown onto Si/SiO2 substrates via xylene pyrolysis using the chemical vapor deposition technique. Polymers like PEDOT:PSS and polyaniline (PANI) mixed with various solvents like DMSO, DMF, 2-propanol and ethylene glycol were used to synthesize the composite films. These sensors exhibited excellent response and selectivity at room temperature when exposed to low concentrations (100 ppm) of analyte gases like NH3 and NO2. The effect of various solvents on the sensor response imparting selectivity to CNT-polymer nanocomposites was investigated extensively. Sensitivities as high as 28% were observed for an MWCNT-PEDOT:PSS composite sensor when exposed to 100 ppm of NH3 and - 29.8% sensitivity for an MWCNT-PANI composite sensor to 100 ppm of NO2 when DMSO was used as a solvent. Additionally, the sensors exhibited good reversibility.

  7. A Micro CO2 Gas Sensor Based on Sensing of pH-Sensitive Hydrogel Swelling by Means of a Pressure Sensor

    NARCIS (Netherlands)

    Herber, S.; Bomer, Johan G.; Olthuis, Wouter; Bergveld, Piet; van den Berg, Albert

    2005-01-01

    In this paper a sensor is presented for the detection of carbon dioxide gas inside the stomach in order to diagnose gastrointestinal ischemia. The operational principle of the sensor is measuring the CO2 induced pressure generation of a confined pH-sensitive hydrogel by means of a micro pressure

  8. Optical waveguide BTX gas sensor based on polyacrylate resin thin film.

    Science.gov (United States)

    Kadir, Razak; Yimit, Abliz; Ablat, Hayrensa; Mahmut, Mamtimin; Itoh, Kiminori

    2009-07-01

    An optical sensor sensitive to BTX has been developed by spin coating a thin film of polyacrylate resin onto a tin- diffused glass optical waveguide. A pair of prism coupler was employed for optical coupling matched with diiodomethane (CH2l2). The guided wave transmits in waveguide layer and passes through the film as an evanescent wave. Polyacrylate film has a strong capacity of absorbing oil gases. The film is stable in N2 but benzene exposure at room temperature can result in rapid and reversible changes of transmittance (7) and refractive index (n1) of this film. It has been demonstrated that the sensor containing a 10 mm boardand about a hundred nanometers thick resin film can detect lower than 8 ppm BTX.

  9. Surface acoustic wave sensor array system for trace organic vapor detection using pattern recognition analysis

    Science.gov (United States)

    Rose-Pehrsson, Susan L.; Grate, Jay W.; Klusty, Mark

    1993-03-01

    A sensor system using surface acoustic wave (SAW) vapor sensors has been fabricated and tested against hazardous organic vapors, simulants of these vapors, and potential background vapors. The vapor tests included two- and three-component mixtures, and covered a wide relative humidity range. The sensor system was compared of four SAW devices coated with different sorbent materials with different vapor selectivities. Preconcentrators were included to improve sensitivity. The vapor experiments were organized into a large data set analyzed using pattern recognition techniques. Pattern recognition algorithms were developed to identify two different classes of hazards. The algorithms were verified against a second data set not included in the training. Excellent sensitivity was achieved by the sensor coatings, and the pattern recognition analysis, and was also examined by the preconcentrators. The system can detect hazardous vapors of interest in the ppb range even in varying relative humidity and in the presence of background vapors. The system does not false alarm to a variety of other vapors including gasoline, jet fuel, diesel fuel and cigarette smoke.

  10. A 94-GHz Millimeter-Wave Sensor for Speech Signal Acquisition

    Directory of Open Access Journals (Sweden)

    Jianqi Wang

    2013-10-01

    Full Text Available High frequency millimeter-wave (MMW radar-like sensors enable the detection of speech signals. This novel non-acoustic speech detection method has some special advantages not offered by traditional microphones, such as preventing strong-acoustic interference, high directional sensitivity with penetration, and long detection distance. A 94-GHz MMW radar sensor was employed in this study to test its speech acquisition ability. A 34-GHz zero intermediate frequency radar, a 34-GHz superheterodyne radar, and a microphone were also used for comparison purposes. A short-time phase-spectrum-compensation algorithm was used to enhance the detected speech. The results reveal that the 94-GHz radar sensor showed the highest sensitivity and obtained the highest speech quality subjective measurement score. This result suggests that the MMW radar sensor has better performance than a traditional microphone in terms of speech detection for detection distances longer than 1 m. As a substitute for the traditional speech acquisition method, this novel speech acquisition method demonstrates a large potential for many speech related applications.

  11. Noise suppression algorithm of short-wave infrared star image for daytime star sensor

    Science.gov (United States)

    Wang, Wenjie; Wei, Xinguo; Li, Jian; Wang, Gangyi

    2017-09-01

    As an important development trend of star sensor technology, research on daytime star sensor technology can expand the applications of star sensor from spacecrafts to airborne vehicles. The biggest problem for daytime star sensor is the detection of dim stars from strong atmospheric background radiation. The use of short-wave infrared (SWIR) technology has been proven to be an effective approach to solve this problem. However, the SWIR star images inevitably contain stripe nonuniformity noise and defective pixels, which degrade the quality of the acquired images and affect the subsequent star spot extraction and star centroiding accuracy seriously. Because the characteristics of stripe nonuniformity and defective pixels in the SWIR star images change with time during a long term continuous operation, the method of one-time off-line calibration is not applicable. To solve this problem, an algorithm of noise suppression for SWIR star image is proposed. It firstly extracts non-background pixels by one-dimensional mean filtering. Then through one-dimensional feature point descriptor, which is used to distinguish the bright star spots pixels from defective pixels, various types of defective pixels are accurately detected. Finally, the method of moment matching is adopted to remove the stripe nonuniformity and the defective pixels are compensated effectively. The simulation experiments results indicates that the proposed algorithm can adaptively and effectively suppress the influence of stripe nonuniformity and defective pixels in SWIR star images and it is beneficial to obtain higher star centroiding accuracy.

  12. A Wearable and Highly Sensitive Graphene Strain Sensor for Precise Home-Based Pulse Wave Monitoring.

    Science.gov (United States)

    Yang, Tingting; Jiang, Xin; Zhong, Yujia; Zhao, Xuanliang; Lin, Shuyuan; Li, Jing; Li, Xinming; Xu, Jianlong; Li, Zhihong; Zhu, Hongwei

    2017-07-28

    Profuse medical information about cardiovascular properties can be gathered from pulse waveforms. Therefore, it is desirable to design a smart pulse monitoring device to achieve noninvasive and real-time acquisition of cardiovascular parameters. The majority of current pulse sensors are usually bulky or insufficient in sensitivity. In this work, a graphene-based skin-like sensor is explored for pulse wave sensing with features of easy use and wearing comfort. Moreover, the adjustment of the substrate stiffness and interfacial bonding accomplish the optimal balance between sensor linearity and signal sensitivity, as well as measurement of the beat-to-beat radial arterial pulse. Compared with the existing bulky and nonportable clinical instruments, this highly sensitive and soft sensing patch not only provides primary sensor interface to human skin, but also can objectively and accurately detect the subtle pulse signal variations in a real-time fashion, such as pulse waveforms with different ages, pre- and post-exercise, thus presenting a promising solution to home-based pulse monitoring.

  13. Millimeter-Wave Chemical Sensor Using Substrate-Integrated-Waveguide Cavity.

    Science.gov (United States)

    Memon, Muhammad Usman; Lim, Sungjoon

    2016-10-31

    This research proposes a substrate-integrated waveguide (SIW) cavity sensor to detect several chemicals using the millimeter-wave frequency range. The frequency response of the presented SIW sensor is switched by filling a very small quantity of chemical inside of the fluidic channel, which also causes a difference in the effective permittivity. The fluidic channel on this structure is either empty or filled with a chemical; when it is empty the structure resonates at 17.08 GHz. There is always a different resonant frequency when any chemical is injected into the fluidic channel. The maximum amount of chemical after injection is held in the center of the SIW structure, which has the maximum magnitude of the electric field distribution. Thus, the objective of sensing chemicals in this research is achieved by perturbing the electric fields of the SIW structure.

  14. Video rate nine-band multispectral short-wave infrared sensor.

    Science.gov (United States)

    Kutteruf, Mary R; Yetzbacher, Michael K; DePrenger, Michael J; Novak, Kyle M; Miller, Corey A; Downes, Trijntje Valerie; Kanaev, Andrey V

    2014-05-01

    Short-wave infrared (SWIR) imaging sensors are increasingly being used in surveillance and reconnaissance systems due to the reduced scatter in haze and the spectral response of materials over this wavelength range. Typically SWIR images have been provided either as full motion video from framing panchromatic systems or as spectral data cubes from line-scanning hyperspectral or multispectral systems. Here, we describe and characterize a system that bridges this divide, providing nine-band spectral images at 30 Hz. The system integrates a custom array of filters onto a commercial SWIR InGaAs array. We measure the filter placement and spectral response. We demonstrate a simple simulation technique to facilitate optimization of band selection for future sensors.

  15. Effects of surface roughness on optical properties and sensitivity of fiber-optic evanescent wave sensors.

    Science.gov (United States)

    Zhong, Nianbing; Zhu, Xun; Liao, Qiang; Wang, Yongzhong; Chen, Rong; Sun, Yahui

    2013-06-10

    The effects of surface roughness on the light transmission properties and sensitivity of fiber-optic evanescent wave sensors are investigated. A simple method of increasing the sensitivity based on the surface roughness (pit depth δ and diameter Δ) and incident angle U(i) of light rays on the fiber input end is proposed. We discovered that as 2δ/Δ increases, the transmitted light intensity decreases, but the sensitivity initially increases and then decreases. In sensors containing fibers of various roughnesses, the sensitivity to glucose solutions reached -11.7 mW/riu at 2δ/Δ=0.32 and increased further to -15.3 mW/riu with proper adjustment of U(i).

  16. Ultra-Trace Chemical Sensing with Long-Wave Infrared Cavity-Enhanced Spectroscopic Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Taubman, Matthew S.; Myers, Tanya L.; Cannon, Bret D.; Williams, Richard M.; Schultz, John F.

    2003-02-20

    The infrared sensors task of Pacific Northwest National Laboratory's (PNNL's) Remote Spectroscopy Project (Task B of Project PL211) is focused on the science and technology of remote and in-situ spectroscopic chemical sensors for detecting proliferation and coun-tering terrorism. Missions to be addressed by remote chemical sensor development in-clude detecting proliferation of nuclear or chemical weapons, and providing warning of terrorist use of chemical weapons. Missions to be addressed by in-situ chemical sensor development include countering terrorism by screening luggage, personnel, and shipping containers for explosives, firearms, narcotics, chemical weapons, or chemical weapons residues, and mapping contaminated areas. The science and technology is also relevant to chemical weapons defense, air operations support, monitoring emissions from chemi-cal weapons destruction or industrial activities, law enforcement, medical diagnostics, and other applications. Sensors for most of these missions will require extreme chemical sensitivity and selectiv-ity because the signature chemicals of importance are expected to be present in low con-centrations or have low vapor pressures, and the ambient air is likely to contain pollutants or other chemicals with interfering spectra. Cavity-enhanced chemical sensors (CES) that draw air samples into optical cavities for laser-based interrogation of their chemical content promise real-time, in-situ chemical detection with extreme sensitivity to specified target molecules and superb immunity to spectral interference and other sources of noise. PNNL is developing CES based on quantum cascade (QC) lasers that operate in the mid-wave infrared (MWIR - 3 to 5 microns) and long-wave infrared (LWIR - 8 to 14 mi-crons), and CES based on telecommunications lasers operating in the short-wave infrared (SWIR - 1 to 2 microns). All three spectral regions are promising because smaller mo-lecular absorption cross sections in the SWIR

  17. Effect of gas on shear wave velocity of sandy soils densified with explosives

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Vega-Posada

    2017-01-01

    Full Text Available Context: Shear wave velocity tests (Vs are commonly used to estimate the increase in resistance of explosive densified soils. In some historical cases, Vs tests performed after the soil improvement process do not show a significant increase in soil resistance, even though the soil surface sits more than 0.50 m. It is believed that this response is due to the presence of gas on the soil mass. Method: This paper presents the results of monotonic triaxial tests performed on samples of dense gaseous sandy soils to evaluate the effect of occluded gas on the response to the shear wave velocity in densified sands with explosives. For sand sampling, it was collected from a loose sand deposit located in South Carolina, USA. These samples were densified in-situ with explosives, and consolidated to the in-situ effective stress conditions, which are considered representative in the conditions of effort at the moment of the densification with explosives. Results: Triaxial tests were performed under global non-drained conditions. The results of these tests show that gas causes the shear wave velocity values obtained for the gaseous sands to approximate the shear wave velocity values obtained in the saturated samples tested under drained conditions. In addition, behavior tends to be more pronounced as the soil is denser. Conclusions: These response may offer some insights as to why the shear wave velocity does not increase significantly in densified soils with explosives, even though the density increases considerably.

  18. An integrated shear-wave velocity model for the Groningen gas field, The Netherlands

    NARCIS (Netherlands)

    Kruiver, Pauline P.; van Dedem, Ewoud; Romijn, Remco; de Lange, Ger; Korff, M.; Stafleu, Jan; Gunnink, Jan L.; Rodriguez-Marek, Adrian; Bommer, Julian J.; van Elk, Jan; Doornhof, Dirk

    2017-01-01

    A regional shear-wave velocity (VS) model has been developed for the Groningen gas field in the Netherlands as the basis for seismic microzonation of an area of more than 1000 km2. The VS model, extending to a depth of almost 1 km, is an essential input to the

  19. Continuous wave optical parametric oscillator for quartz-enhanced photoacoustic trace gas sensing

    NARCIS (Netherlands)

    Ngai, A.K.Y.; Persijn, S.T.; Lindsay, I.D.; Kosterev, A.A.; Gross, P.; Lee, C.J.; Cristescu, S.M.; Tittel, F.K.; Boller, K.J.; Harren, F.J.M.

    2007-01-01

    A continuous wave optical parametric oscillator, generating up to 300 mW idler output in the 3-4 mu m wavelength region, and pumped by a fiber-amplified DBR diode laser is used for trace gas detection by means of quartz-enhanced photoacoustic spectroscopy (QEPAS). Mode-hop-free tuning of the OPO

  20. Continuous wave optical parametric oscillator for quartz enhanced photoacoustic trace gas sensing

    NARCIS (Netherlands)

    Ngai, A.K.Y.; Persijn, S.T.; Lindsay, I.D.; Kosterev, A.A.; Gross, P.; Lee, Christopher James; Cristescu, S.M.; Tittel, F.K.; Boller, Klaus J.; Harren, F.J.M.

    2007-01-01

    A continuous wave optical parametric oscillator, generating up to 300 mW idler output in the 3–4 μm wavelength region, and pumped by a fiber-amplified DBR diode laser is used for trace gas detection by means of quartz-enhanced photoacoustic spectroscopy (QEPAS). Mode-hop-free tuning of the OPO

  1. Appropriate conditions to realize a p -wave superfluid state starting from a spin-orbit-coupled s -wave superfluid Fermi gas

    Science.gov (United States)

    Yamaguchi, T.; Inotani, D.; Ohashi, Y.

    2017-05-01

    We theoretically investigate a spin-orbit-coupled s -wave superfluid Fermi gas, to examine the time evolution of the system, after an s -wave pairing interaction is replaced by a p -wave one at t =0 . In our recent paper [T. Yamaguchi, D. Inotani, and Y. Ohashi, J. Phys. Soc. Jpn. 86, 013001 (2017), 10.7566/JPSJ.86.013001], we proposed that this manipulation may realize a p -wave superfluid Fermi gas because the p -wave pair amplitude that is induced in the s -wave superfluid state by a parity-broken antisymmetric spin-orbit interaction gives a nonvanishing p -wave superfluid order parameter, immediately after the p -wave interaction is turned on. In this paper, using a time-dependent Bogoliubov-de Gennes theory, we assess this idea under various conditions with respect to the s -wave and p -wave interaction strengths, as well as the spin-orbit coupling strength. From these, we clarify that the momentum distribution of Fermi atoms in the initial s -wave state (t gas physics, our results may provide a possible way to accomplish this.

  2. Gas Sensors Based on Tin Oxide Nanoparticles Synthesized from a Mini-Arc Plasma Source

    Directory of Open Access Journals (Sweden)

    Ganhua Lu

    2006-01-01

    Full Text Available Miniaturized gas sensors or electronic noses to rapidly detect and differentiate trace amount of chemical agents are extremely attractive. In this paper, we report on the fabrication and characterization of a functional tin oxide nanoparticle gas sensor. Tin oxide nanoparticles are first synthesized using a convenient and low-cost mini-arc plasma source. The nanoparticle size distribution is measured online using a scanning electrical mobility spectrometer (SEMS. The product nanoparticles are analyzed ex-situ by high resolution transmission electron microscopy (HRTEM for morphology and defects, energy dispersive X-ray (EDX spectroscopy for elemental composition, electron diffraction for crystal structure, and X-ray photoelectron spectroscopy (XPS for surface composition. Nonagglomerated rutile tin oxide (SnO2 nanoparticles as small as a few nm have been produced. Larger particles bear a core-shell structure with a metallic core and an oxide shell. The nanoparticles are then assembled onto an e-beam lithographically patterned interdigitated electrode using electrostatic force to fabricate the gas sensor. The nanoparticle sensor exhibits a fast response and a good sensitivity when exposed to 100 ppm ethanol vapor in air.

  3. Extremely sensitive CWA analyzer based on a novel optical pressure sensor in photoacoustic gas analysis

    Science.gov (United States)

    Kauppinen, Jyrki K.; Koskinen, Vesa; Uotila, Juho; Kauppinen, Ismo K.

    2004-12-01

    Major improvement into the sensitivity of broadband Fourier transform infrared (FTIR) spectrometers, used in gas analysis, can be achieved by a photoacoustic detection system, which bases on a recently introduced optical pressure sensor. The sensor is a cantilever-type microphone with interferometric measurement of its free end displacement. By using a preliminary prototype of the photoacoustic gas detector, equipped with the proposed sensor and a black body radiation source, a detection limit in the sub-ppb range was obtained for e.g. methane gas. The limit, obtained in non-resonant operation mode, is very close to the best photoacoustic results achieved with powerfull laser sources and by exploiting the cell resonances. It is also orders of magnitude better than any measurement with a black body radiation source. Furthermore, the ultimate sensitivity leads on to very small detection limits also for several chemical warfare agents (CWA) e.g. sarin, tabun and mustard. The small size of the sensor and its great thermal stability enables the construction of an extremely sensitive portable CWA analyzer in the near future.

  4. Solution-Processed Gas Sensors Employing SnO2 Quantum Dot/MWCNT Nanocomposites.

    Science.gov (United States)

    Liu, Huan; Zhang, Wenkai; Yu, Haoxiong; Gao, Liang; Song, Zhilong; Xu, Songman; Li, Min; Wang, Yang; Song, Haisheng; Tang, Jiang

    2016-01-13

    Solution-processed SnO2 colloidal quantum dots (CQDs) have emerged as an important new class of gas-sensing materials due to their potential for low-cost and high-throughput fabrication. Here we employed the design strategy based on the synergetic effect from highly sensitive SnO2 CQDs and excellent conductive properties of multiwalled carbon nanotubes (MWCNTs) to overcome the transport barrier in CQD gas sensors. The attachment and coverage of SnO2 CQDs on the MWCNT surfaces were achieved by simply mixing the presynthesized SnO2 CQDs and MWCNTs at room temperature. Compared to the pristine SnO2 CQDs, the sensor based on SnO2 quantum dot/MWCNT nanocomposites exhibited a higher response upon exposure to H2S, and the response toward 50 ppm of H2S at 70 °C was 108 with the response and recovery time being 23 and 44 s. Because of the favorable energy band alignment, the MWCNTs can serve as the acceptor of the electrons that are injected from H2S into SnO2 quantum dots in addition to the charge transport highway to direct the electron flow to the electrode, thereby enhancing the sensor response. Our research results open an easy pathway for developing highly sensitive and low-cost gas sensors.

  5. Design and Implementation of an Intelligent Expansion Module for Wireless Gas Sensor Networks

    Directory of Open Access Journals (Sweden)

    Grigore STAMATESCU

    2015-04-01

    Full Text Available Wireless gas sensor networks (WGSN offer the potential of high spatial and temporal resolution monitoring of target areas in both critical and non-critical scenarios. We describe the design and evaluation of an electronic expansion module, MICARES, suitable for gas sensing applications with wireless sensor networks. The module is intended for use with the MICA family of motes through the 51-pin connector. Proper housing assured, the device is applicable to both indoor and outdoor gas sensing for buildings, commercial and industrial spaces. Challenges lay in sensor selection, analytical and experimental power budgeting and field testing. We present the design goals at the network and node level and the adopted solutions to achieve them. Appropriate adaptive sampling strategies for energy efficiency, along with data resulting from CO2 monitoring are described. Emphasis is put on embedded sensor integration into the electrical design and methods for on-board data acquisition and processing for decision support at the node and network levels.

  6. A Micro-Resonant Gas Sensor with Nanometer Clearance between the Pole Plates

    Directory of Open Access Journals (Sweden)

    Xiaorui Fu

    2018-01-01

    Full Text Available In micro-resonant gas sensors, the capacitive detection is widely used because of its simple structure. However, its shortcoming is a weak signal output caused by a small capacitance change. Here, we reduced the initial clearance between the pole plates to the nanometer level, and increased the capacitance between the pole plates and its change during resonator vibration. We propose a fabricating process of the micro-resonant gas sensor by which the initial clearance between the pole plates is reduced to the nanometer level and a micro-resonant gas sensor with 200 nm initial clearance is fabricated. With this sensor, the resonant frequency shifts were measured when they were exposed to several different vapors, and high detection accuracies were obtained. The detection accuracy with respect to ethanol vapor was 0.4 ppm per Hz shift, and the detection accuracy with respect to hydrogen and ammonias vapors was 3 ppm and 0.5 ppm per Hz shift, respectively.

  7. Fast Response and High Sensitivity ZnO/glass Surface Acoustic Wave Humidity Sensors Using Graphene Oxide Sensing Layer

    Science.gov (United States)

    Xuan, Weipeng; He, Mei; Meng, Nan; He, Xingli; Wang, Wenbo; Chen, Jinkai; Shi, Tianjin; Hasan, Tawfique; Xu, Zhen; Xu, Yang; Luo, J. K.

    2014-01-01

    We report ZnO/glass surface acoustic wave (SAW) humidity sensors with high sensitivity and fast response using graphene oxide sensing layer. The frequency shift of the sensors is exponentially correlated to the humidity change, induced mainly by mass loading effect rather than the complex impedance change of the sensing layer. The SAW sensors show high sensitivity at a broad humidity range from 0.5%RH to 85%RH with humidity sensors, complemented with full humidity range measurement, highlights their potential in a wide range of applications. PMID:25425458

  8. Shock-wave proton acceleration from a hydrogen gas jet

    Science.gov (United States)

    Cook, Nathan; Pogorelsky, Igor; Polyanskiy, Mikhail; Babzien, Marcus; Tresca, Olivier; Maharjan, Chakra; Shkolnikov, Peter; Yakimenko, Vitaly

    2013-04-01

    Typical laser acceleration experiments probe the interaction of intense linearly-polarized solid state laser pulses with dense metal targets. This interaction generates strong electric fields via Transverse Normal Sheath Acceleration and can accelerate protons to high peak energies but with a large thermal spectrum. Recently, the advancement of high pressure amplified CO2 laser technology has allowed for the creation of intense (10^16 Wcm^2) pulses at λ˜10 μm. These pulses may interact with reproducible, high rep. rate gas jet targets and still produce plasmas of critical density (nc˜10^19 cm-3), leading to the transference of laser energy via radiation pressure. This acceleration mode has the advantage of producing narrow energy spectra while scaling well with pulse intensity. We observe the interaction of an intense CO2 laser pulse with an overdense hydrogen gas jet. Using two pulse optical probing in conjunction with interferometry, we are able to obtain density profiles of the plasma. Proton energy spectra are obtained using a magnetic spectrometer and scintillating screen.

  9. Chlorine gas sensors using one-dimensional tellurium nanostructures.

    Science.gov (United States)

    Sen, Shashwati; Sharma, Madhvi; Kumar, Vivek; Muthe, K P; Satyam, P V; Bhatta, Umananda M; Roy, M; Gaur, N K; Gupta, S K; Yakhmi, J V

    2009-03-15

    Tellurium nanotubes have been grown by physical vapor deposition under inert environment at atmospheric pressure as well as under vacuum conditions. Different techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and optical absorption have been utilized for characterization of grown structures. Films prepared using both types of tellurium nanotubes were characterized for sensitivity to oxidizing and reducing gases and it was found that the relative response to gases depends on the microstructure. Nanotubes prepared at atmospheric pressure (of argon) showed high sensitivity and better selectivity to chlorine gas. Impedance spectroscopy studies showed that the response to chlorine is mainly contributed by grain boundaries and is therefore enhanced for nanotubes prepared under argon atmosphere.

  10. Modeling and Experimental Study on Characterization of Micromachined Thermal Gas Inertial Sensors

    Directory of Open Access Journals (Sweden)

    Yan Su

    2010-09-01

    Full Text Available Micromachined thermal gas inertial sensors based on heat convection are novel devices that compared with conventional micromachined inertial sensors offer the advantages of simple structures, easy fabrication, high shock resistance and good reliability by virtue of using a gaseous medium instead of a mechanical proof mass as key moving and sensing elements. This paper presents an analytical modeling for a micromachined thermal gas gyroscope integrated with signal conditioning. A simplified spring-damping model is utilized to characterize the behavior of the sensor. The model relies on the use of the fluid mechanics and heat transfer fundamentals and is validated using experimental data obtained from a test-device and simulation. Furthermore, the nonideal issues of the sensor are addressed from both the theoretical and experimental points of view. The nonlinear behavior demonstrated in experimental measurements is analyzed based on the model. It is concluded that the sources of nonlinearity are mainly attributable to the variable stiffness of the sensor system and the structural asymmetry due to nonideal fabrication.

  11. Gas Sensors Based on Locally Heated Multiwall Carbon Nanotubes Decorated with Metal Nanoparticles

    Directory of Open Access Journals (Sweden)

    R. Savu

    2015-01-01

    Full Text Available We report the design and fabrication of microreactors and sensors based on metal nanoparticle-decorated carbon nanotubes. Titanium adhesion layers and gold films were sputtered onto Si/SiO2 substrates for obtaining the electrical contacts. The gold layers were electrochemically thickened until 1 μm and the electrodes were patterned using photolithography and wet chemical etching. Before the dielectrophoretic deposition of the nanotubes, a gap 1 μm wide and 5 μm deep was milled in the middle of the metallic line by focused ion beam, allowing the fabrication of sensors based on suspended nanotubes bridging the electrodes. Subsequently, the sputtering technique was used for decorating the nanotubes with metallic nanoparticles. In order to test the as-obtained sensors, microreactors (100 μL volume were machined from a single Kovar piece, being equipped with electrical connections and 1/4′′ Swagelok-compatible gas inlet and outlets for controlling the atmosphere in the testing chamber. The sensors, electrically connected to the contact pins by wire-bonding, were tested in the 10−5 to 10−2 W working power interval using oxygen as target gas. The small chamber volume allowed the measurement of fast characteristic times (response/recovery, with the sensors showing good sensitivity.

  12. Low-Power, Chip-Scale, Carbon Dioxide Gas Sensors for Spacesuit Monitoring

    Science.gov (United States)

    Rani, Asha; Shi, Chen; Thomson, Brian; Debnath, Ratan; Wen, Boamei; Motayed, Abhishek; Chullen, Cinda

    2018-01-01

    N5 Sensors, Inc. through a Small Business Technology Transfer (STTR) contract award has been developing ultra-small, low-power carbon dioxide (CO2) gas sensors, suited for monitoring CO2 levels inside NASA spacesuits. Due to the unique environmental conditions within the spacesuits, such as high humidity, large temperature swings, and operating pressure swings, measurement of key gases relevant to astronaut's safety and health such as(CO2), is quite challenging. Conventional non-dispersive infrared absorption based CO2 sensors present challenges inside the spacesuits due to size, weight, and power constraints, along with the ability to sense CO2 in a high humidity environment. Unique chip-scale, nanoengineered chemiresistive gas-sensing architecture has been developed for this application, which can be operated in a typical space-suite environmental conditions. Unique design combining the selective adsorption properties of the nanophotocatalytic clusters of metal-oxides and metals, provides selective detection of CO2 in high relative humidity conditions. All electronic design provides a compact and low-power solution, which can be implemented for multipoint detection of CO2 inside the spacesuits. This paper will describe the sensor architecture, development of new photocatalytic material for better sensor response, and advanced structure for better sensitivity and shorter response times.

  13. In situ 2-D piezoelectric wafer active sensors arrays for guided wave damage detection.

    Science.gov (United States)

    Yu, Lingyu; Giurgiutiu, Victor

    2008-04-01

    This paper presented development work of an in situ method for damage detection in thin-wall structures using embedded two-dimensional ultrasonic phased arrays. Piezoelectric wafer active sensors were used to generate and receive guided Lamb waves propagating in the plate-like structure. The development of a generic beamforming algorithm that does not require parallel ray assumption through using full wave propagation paths is described. A virtual beam steering method and device, the embedded ultrasonic structural radar, was implemented as a signal post-processing procedure. Several two-dimensional configurations were investigated and compared with beamforming simulation. Finally, rectangular shape arrays were developed for verifying the generic formulas and omnidirectionality. The rectangular arrays yield good directionality within the 360 degrees full range and are able to detect damage anywhere in the entire plate.

  14. Gas transfer under breaking waves: experiments and an improved vorticity-based model

    Directory of Open Access Journals (Sweden)

    V. K. Tsoukala

    2008-07-01

    Full Text Available In the present paper a modified vorticity-based model for gas transfer under breaking waves in the absence of significant wind forcing is presented. A theoretically valid and practically applicable mathematical expression is suggested for the assessment of the oxygen transfer coefficient in the area of wave-breaking. The proposed model is based on the theory of surface renewal that expresses the oxygen transfer coefficient as a function of both the wave vorticity and the Reynolds wave number for breaking waves. Experimental data were collected in wave flumes of various scales: a small-scale experiments were carried out using both a sloping beach and a rubble-mound breakwater in the wave flume of the Laboratory of Harbor Works, NTUA, Greece; b large-scale experiments were carried out with a sloping beach in the wind-wave flume of Delft Hydraulics, the Netherlands, and with a three-layer rubble mound breakwater in the Schneideberg Wave Flume of the Franzius Institute, University of Hannover, Germany. The experimental data acquired from both the small- and large-scale experiments were in good agreement with the proposed model. Although the apparent transfer coefficients from the large-scale experiments were lower than those determined from the small-scale experiments, the actual oxygen transfer coefficients, as calculated using a discretized form of the transport equation, are in the same order of magnitude for both the small- and large-scale experiments. The validity of the proposed model is compared to experimental results from other researchers. Although the results are encouraging, additional research is needed, to incorporate the influence of bubble mediated gas exchange, before these results are used for an environmental friendly design of harbor works, or for projects involving waste disposal at sea.

  15. Deployment Algorithms of Wireless Sensor Networks for Near-surface Underground Oil and Gas Pipeline Monitoring

    Directory of Open Access Journals (Sweden)

    Hua-Ping YU

    2014-07-01

    Full Text Available Oil and gas pipelines are the infrastructure of national economic development. Deployment problem of wireless underground sensor networks (WUSN for oil and gas pipeline systems is a fundamental problem. This paper firstly analyzed the wireless channel characteristics and energy consumption model in near-surface underground soil, and then studied the spatial structure of oil and gas pipelines and introduced the three-layer system structure of WUSN for oil and gas pipelines monitoring. Secondly, the optimal deployment strategy in XY plane and XZ plane which were projected from three-dimensional oil and gas pipeline structure was analyzed. Thirdly, the technical framework of using kinetic energy of the fluid in pipelines to recharge sensor nodes and partition strategy for energy consumption balance based on the wireless communication technology of magnetic induction waveguide were proposed, which can effectively improve the energy performance and connectivity of the network, and provide theoretical guidance and practical basis for the monitoring of long oil and gas pipeline network, the city tap water pipe network and sewage pipe network.

  16. Wave propagation versus transient ground displacement as a credible hazard to buried oil and gas pipelines

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-07-01

    The cause of damage to a natural gas pipeline during the 1994 Northridge earthquake in the San Fernando Valley in California was examined in a collaborative effort by Southern California Gas Co., Pacific Gas and Electric Co., and with support from Tokyo Gas, Osaka Gas and Toho Gas. Extensive field and laboratory studies were conducted on a 1925 gas pipeline that suffered several girth weld failures in Potrero Canyon where significant ground displacement was observed. Ground cracking and sand boils were observed in the area following the earthquake but there were few other signs of permanent ground deformation near the pipeline damage. Damage consisted mostly of girth weld tensile failure and two cases of buckling of the pipe wall. Initial evidence suggested that the damage may have been caused by wave propagation, but a detailed study has shown that wave propagation effect was not a significant factor in the pipeline damage. A simple analytical model was developed to determine the transient ground deformation that might have occurred in the area of the pipeline damage. The model also provides clues regarding the cause of the ground cracking observed at the margins of the canyon. It also provides approximate magnitudes of differential ground displacements resulting from the earthquake. The model also considers the reasons for spatial distribution of pipeline damage. 13 refs., 1 tab., 6 figs.

  17. Integration of a wave rotor to an ultra-micro gas turbine (UmuGT)

    Science.gov (United States)

    Iancu, Florin

    2005-12-01

    Wave rotor technology has shown a significant potential for performance improvement of thermodynamic cycles. The wave rotor is an unsteady flow machine that utilizes shock waves to transfer energy from a high energy fluid to a low energy fluid, increasing both the temperature and the pressure of the low energy fluid. Used initially as a high pressure stage for a gas turbine locomotive engine, the wave rotor was commercialized only as a supercharging device for internal combustion engines, but recently there is a stronger research effort on implementing wave rotors as topping units or pressure gain combustors for gas turbines. At the same time, Ultra Micro Gas Turbines (UmuGT) are expected to be a next generation of power source for applications from propulsion to power generation, from aerospace industry to electronic industry. Starting in 1995, with the MIT "Micro Gas Turbine" project, the mechanical engineering research world has explored more and more the idea of "Power MEMS". Microfabricated turbomachinery like turbines, compressors, pumps, but also electric generators, heat exchangers, internal combustion engines and rocket engines have been on the focus list of researchers for the past 10 years. The reason is simple: the output power is proportional to the mass flow rate of the working fluid through the engine, or the cross-sectional area while the mass or volume of the engine is proportional to the cube of the characteristic length, thus the power density tends to increase at small scales (Power/Mass=L -1). This is the so-called "cube square law". This work investigates the possibilities of incorporating a wave rotor to an UmuGT and discusses the advantages of wave rotor as topping units for gas turbines, especially at microscale. Based on documented wave rotor efficiencies at larger scale and subsidized by both, a gasdynamic model that includes wall friction, and a CFD model, the wave rotor compression efficiency at microfabrication scale could be estimated

  18. A Solitary Wave-Based Sensor to Monitor the Setting of Fresh Concrete

    Directory of Open Access Journals (Sweden)

    Piervincenzo Rizzo

    2014-07-01

    Full Text Available We present a proof-of-principle study about the use of a sensor for the nondestructive monitoring of strength development in hydrating concrete. The nondestructive evaluation technique is based on the propagation of highly nonlinear solitary waves (HNSWs, which are non-dispersive mechanical waves that can form and travel in highly nonlinear systems, such as one-dimensional particle chains. A built-in transducer is adopted to excite and detect the HNSWs. The waves are partially reflected at the transducer/concrete interface and partially transmitted into the concrete. The time-of-flight and the amplitude of the waves reflected at the interface are measured and analyzed with respect to the hydration time, and correlated to the initial and final set times established by the penetration test (ASTM C 403. The results show that certain features of the HNSWs change as the concrete curing progresses indicating that it has the potential of being an efficient, cost-effective tool for monitoring strengths/stiffness development.

  19. Assessment of a combined gas chromatography mass spectrometer sensor system for detecting biologically relevant volatile compounds.

    Science.gov (United States)

    Gould, Oliver; Wieczorek, Tom; de Lacy Costello, Ben; Persad, Raj; Ratcliffe, Norman

    2017-12-06

    There have been a number of studies in which metal oxide sensors (MOS) have replaced conventional analytical detectors in gas chromatography systems. However, despite the use of these instruments in a range of applications including breath research the sensor responses (i.e. resistance changes w.r.t. concentration of VCs) remain largely unreported. This paper addresses that issue by comparing the response of a metal oxide sensor directly with a mass spectrometer (MS), whereby both detectors are interfaced to the same GC column using an s-swafer. It was demonstrated that the sensitivity of an in-house fabricated ZnO/SnO 2 thick film MOS was superior to a modern MS for the detection of a wide range of volatile compounds (VCs) of different functionalities and masses. Better techniques for detection and quantification of these VCs is valuable, as many of these compounds are commonly reported throughout the scientific literature. This is also the first published report of a combined GC-MS sensor system. These two different detector technologies when combined, should enhance discriminatory abilities to aid disease diagnoses using volatiles from e.g. breath, and bodily fluids. Twenty-nine chemical standards have been tested using solid phase micro-extraction; 25 of these compounds are found on human breath. In all but two instances the sensor exhibited the same or superior limit of detection compared to the MS. Twelve stool samples from healthy participants were analysed; the sensor detected, on average 1.6 peaks more per sample than the MS. Similarly, analysing the headspace of E. coli broth cultures the sensor detected 6.9 more peaks per sample versus the MS. This greater sensitivity is primarily a function of the superior limits of detection of the metal oxide sensor. This shows that systems based on the combination of chromatography systems with solid state sensors shows promise for a range of applications.

  20. Laboratory-based validation of the baseline sensors of the ITER diagnostic residual gas analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Biewer, Theodore M. [ORNL; Marcus, Chris [ORNL; Klepper, C Christopher [ORNL; Andrew, Philip [ITER Organization, Cadarache, France; Gardner, W. L. [United States ITER Project Office; Graves, Van B. [ORNL; Hughes, Shaun [ITER Organization, Saint Paul Lez Durance, France

    2017-10-01

    The divertor-specific ITER Diagnostic Residual Gas Analyzer (DRGA) will provide essential information relating to DT fusion plasma performance. This includes pulse-resolving measurements of the fuel isotopic mix reaching the pumping ducts, as well as the concentration of the helium generated as the ash of the fusion reaction. In the present baseline design, the cluster of sensors attached to this diagnostic's differentially pumped analysis chamber assembly includes a radiation compatible version of a commercial quadrupole mass spectrometer, as well as an optical gas analyzer using a plasma-based light excitation source. This paper reports on a laboratory study intended to validate the performance of this sensor cluster, with emphasis on the detection limit of the isotopic measurement. This validation study was carried out in a laboratory set-up that closely prototyped the analysis chamber assembly configuration of the baseline design. This includes an ITER-specific placement of the optical gas measurement downstream from the first turbine of the chamber's turbo-molecular pump to provide sufficient light emission while preserving the gas dynamics conditions that allow for \\textasciitilde 1 s response time from the sensor cluster [1].