• Title, Summary, Keyword: Gas sensor

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Thick-film ammonia gas sensor with high sensitivity and excellent selectivity

  • Lee, Kyuchung;Ryu, Kwang-Ryul;Hur, Chang-Wu
    • Journal of information and communication convergence engineering
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    • v.2 no.1
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    • pp.22-25
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    • 2004
  • A highly sensitive ammonia gas sensor using thick-film technology has been fabricated and examined. The sensing material of the gas sensor is FeOx-$WO_{3}-SnO_{2}$ oxide semiconductor. The sensor exhibits resistance increase upon exposure to low concentration of ammonia gas. The resistance of the sensor is decreased, on the other hand, for exposure to reducing gases such as ethyl alcohol, methane, propane and carbon monoxide. A novel method for detecting ammonia gas quite selectively utilizing a sensor array consisting of an ammonia gas sensor and a compensation element has been proposed and developed. The compensation element is a Pt-doped $WO_{3}-SnO_{2}$gas sensor which shows opposite direction of resistance change in comparison with the ammonia gas sensor upon exposure to ammonia gas. Excellent selectivity has been achieved using the sensor array having two sensing elements.

The Detection Characterization of NOX Gas Using the MWCNT/ZnO Composite Film Gas Sensors by Heat Treatment (열처리에 따른 MWCNT/ZnO 복합체 필름 가스센서의 NOX 가스 검출 특성)

  • Kim, Hyun-Soo;Jang, Kyung-Uk
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.31 no.7
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    • pp.521-526
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    • 2018
  • In particular, gas sensors require characteristics such as high speed, sensitivity, and selectivity. In this study, we fabricated a $NO_X$ gas sensor by using a multi-walled carbon nanotube (MWCNT)/zinc oxide (ZnO) composite film. The fabricated MWCNT/ZnO gas sensor was then treated by a $450^{\circ}C$ temperature process to increase its detection sensitivity for NOx gas. We compared the detection characteristics of a ZnO film gas sensor, MWCNT film gas sensor, and the MWCNT/ZnO composited film gas sensor with and without the heat-treatment process. The fabricated gas sensors were used to detect $NO_X$ gas at different concentrations. The gas sensor absorbed $NO_X$ gas molecules, exhibiting increased sensitivity. The sensitivity of the gas sensor was increased by increasing the gas concentration. Additionally, while changing the temperature inside the chamber for the MWCNT/ZnO composite film gas sensor, we obtained its sensitivity for detecting $NO_X$ gas. Compared with ZnO, the MWCNT film gas sensor is excellent for detecting $NO_X$ gas. From the experimental results, we confirmed the enhanced gas sensor sensing mechanism. The increased effect by electronic interaction between the MWCNT and ZnO films contributes to the improved sensor performance.

Semiconductor-Type MEMS Gas Sensor for Real-Time Environmental Monitoring Applications

  • Moon, Seung Eon;Choi, Nak-Jin;Lee, Hyung-Kun;Lee, Jaewoo;Yang, Woo Seok
    • ETRI Journal
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    • v.35 no.4
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    • pp.617-624
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    • 2013
  • Low power consuming and highly responsive semiconductor-type microelectromechanical systems (MEMS) gas sensors are fabricated for real-time environmental monitoring applications. This subsystem is developed using a gas sensor module, a Bluetooth module, and a personal digital assistant (PDA) phone. The gas sensor module consists of a $NO_2$ or CO gas sensor and signal processing chips. The MEMS gas sensor is composed of a microheater, a sensing electrode, and sensing material. Metal oxide nanopowder is drop-coated onto a substrate using a microheater and integrated into the gas sensor module. The change in resistance of the metal oxide nanopowder from exposure to oxidizing or deoxidizing gases is utilized as the principle mechanism of this gas sensor operation. The variation detected in the gas sensor module is transferred to the PDA phone by way of the Bluetooth module.

Fabrication and Characteristics of Micro-Electro-Mechanical-System-Based Gas Flow Sensor

  • Choi, Ju-Chan;Lee, June-Kyoo;Kong, Seong-Ho
    • Journal of Sensor Science and Technology
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    • v.20 no.6
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    • pp.363-367
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    • 2011
  • This paper proposes a highly-sensitive gas flow sensor with a simple structure. The sensor is composed of a micro-heater for heating the gas medium and a pair of temperature sensors for detecting temperature differences due to gas flow in a sealed chamber on one axis. Operation of the gas flow sensor depends on the transfer of heat through the air medium. The proposed gas flow sensor has the capability to measure gas flow rates <5 $cm^3$/min with a resolution of approximately 0.01 $cm^3$/min. Furthermore, this paper reports some additional experiment results, including the sensitivity of the proposed gas flow sensor as a function of operating current and the flow of different types of gas(oxygen, carbon dioxide, and nitrogen). The fabrication process of the proposed sensor is very simple, making it a good candidate for mass production.

The Analysis of Mechanism for the Gas Sensor of MWCNT/ZnO Composites Film Using the NOX Gas Detection Characteristics (NOX 가스 검출 특성을 이용한 MWCNT/ZnO 복합체 필름 가스 센서의 메커니즘 분석)

  • Son, Ju-Hyung;Kim, Hyun-Soo;Park, Yong-Seo;Jang, Kyung-Uk
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.31 no.3
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    • pp.188-192
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    • 2018
  • In this study, we fabricated an $NO_X$ gas sensor using a composite film of multi-walled carbon nanotubes (MWCNT)/zinc oxide (ZnO). Carbon nanotubes (CNTs) show good electronic conductivity and chemical-stability, and zinc oxide (ZnO) is a wide band gap semiconductor with a large exciton binding energy. Gas sensors require characteristics such as high speed, sensitivity, and selectivity. The fabricated gas sensor was used to detect $NO_X$ gas at different $NO_X$ concentrations. The sensitivity of the gas sensor increased with increasing gas concentrations. Additionally, while changing the temperature inside the chamber containing the MWCNT/ZnO gas sensor, we obtained the sensitivity and normalized responses for detecting $NO_X$ gas in comparison to ZnO and MWCNT film gas sensors. From the experimental results, we confirmed that the gas sensor sensing mechanism was enhanced in the composite-film gas-sensor and that the electronic interaction between MWCNT and ZnO contributed to the improved sensor performance.

NOx Gas Detection Characteristics of MWCNT Gas Sensor by Electrode Spacing Variation (MWCNT 가스센서의 전극 간극 변화에 따른 NOx 가스 검출 특성)

  • Kim, Hyun-Soo;Jang, Kyung-Uk
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.10
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    • pp.668-672
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    • 2014
  • Carbon nanotubes(CNT) has chemical stability and great sensitivity characteristics. In particular, the gas sensor required characteristics such as rapid, selectivity and sensitivity sensor. Therefore, CNT are ideal materials to gas sensor. So, we fabricated the NOx gas sensors of MOS-FET type using the MWCNT (multi-walled carbon nanotube). The fabricated sensor was used to detect the NOx gas for the variation of $V_{gs}$(gate-source voltage) and electrode changed electrode spacing=30, 60, 90[${\mu}m$]. The gas sensor absorbed with the NOx gas molecules showed the decrease of resistance, and the sensitivity of sensor was increased by magnification of electrode spacing. Furthermore, when the voltage($V_{gs}$) was applied to the gas sensor, the decrease in resistance was increased. On the other hand, the sensor sensitivity for the injection of NOx gas was the highest value at the electrode spacing $90[{\mu}m]$. We also obtained the adsorption energy($U_a$) using the Arrhenius plots by the reduction of resistance due to the voltage variations. As a result, we obtained that the adsorption energy was increased with the increment of the applied voltages.

Evaluation of Metal Oxide Semiconductor and Electrochemical Gas Sensor Array Characterization for Measuring Wastewater Odor (폐수의 악취측정을 위한 금속산화물 반도체 및 전기화학식 가스센서 어레이 특성 평가)

  • Yim, Bongbeen;Lee, Seok-Jun;Kim, Sun-Tae
    • Journal of Sensor Science and Technology
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    • v.24 no.1
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    • pp.29-34
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    • 2015
  • This study aimed to evaluate the characterization of a metal oxide semiconductor and electrochemical gas sensor array for measuring wastewater odor. The sensitivity of all gas sensors observed in sampling method by stripping was 6.7 to 20.6 times higher than that by no stripping, except sensor D (electrochemical gas sensor). The average reduction ratio of sensor signal as a function of initial dilution rate of wastewater was in the order of food plant > food waste reutilization facility > plating plant. The sensitivity of gas sensors was dependent on both the type of wastewater and the dilution rate. The sensor signals observed by the gas sensor array were correlated with the dilution factor (OU) calculated by the air dilution sensory test with several wastewater ($r^2=0.920{\sim}0.997$), except the sensor signals of sensor D measured in the plating plant wastewater. It seems likely that the gas sensor array plays a role in the evaluation of odor in wastewater and is useful tool for on-site odor monitoring in the wastewater facilities.

Properties of Non-dispersive infrared Ethanol Gas Sensors according to the Irradiation Energy

  • Kim, JinHo;Yi, SeungHwan
    • Journal of Sensor Science and Technology
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    • v.26 no.3
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    • pp.168-172
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    • 2017
  • A nondispersive infrared (NDIR) ethanol gas sensor was prototyped with ASIC implemented thermopile sensor, which included a temperature sensor and two ellipsoidal waveguide structures. The temperature dependency of the two ethanol sensors (with partially blocked and intact structures) has been characterized. The two ethanol gas sensors showed linear output voltages initially when varying the ambient temperature from 253 K to 333 K. The slope of the temperature sensor presented a constant value of 15 mV/K. After temperature compensation, the ethanol gas sensor estimated ethanol concentrations with larger errors of 20 to 25% below 200 ppm. However, the estimation errors were reduced to between -10 and +1 % from 253 K to 333 K above 200 ppm ethanol gas concentration in this research.

A Study on Thermal Performances of Micro Gas Sensor with Micro Hotplate (마이크로 핫플레이트를 갖는 마이크로 가스센서의 열적성능에 관한 연구)

  • Joo, Young-Cheol;Im, Jun-Hyoung;Lee, Joon-Hun;Kim, C.K.
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.5
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    • pp.278-285
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    • 2006
  • A micro hotplate for micro gas sensor was fabricated by MEMS technology. In order to heat up the gas sensing material to a target temperature, a micro hotplate was built on the gas sensor. The sensing material was deposited on the heater and electrodes, and did not contact with the silicon base to minimize the heat loss to the silicon base. The electric power to heat up the gas sensor was measured. The temperature distribution of micro gas sensor was analyzed by a CFD program. The predicted electric power to heat up th sensing material showed a good agreement with the measured data. The design of micro gas sensor could be modified to increase the temperature uniformity and to decrease the electric power consumption by optimizing the layout of micro hotplate and electrodes.

A Study of Thermal Performances for Micro Gas Sensor (마이크로 가스센서의 열적 성능에 관한 연구)

  • Joo Young-Cheol;Kim Chang-Kyo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.6
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    • pp.531-537
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    • 2006
  • A lever type $NO_2$ micro gas sensor was fabricated by MEMS technology. In order to heat up the gas sensing material to a target temperature, a micro heater was built on the gas sensor. The sensing material laid on the heater and electrodes and did not contact with the silicon base to minimize the heat loss to the silicon base. The electric power to heat up the gas sensor to a target temperature was measured. The temperature distribution of micro gas sensor was analyzed by a CFD program. The predicted electric power of micro heater to heat up the sensing material to the target temperature showed a good agreement with the measured data. The design of micro gas sensor could be modified to show more uniform temperature distribution and to consume less electric power by optimizing the layout of micro heater and electrodes.