WO2022145335A1 - Gas sensor and sensor circuit - Google Patents

Gas sensor and sensor circuit Download PDF

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Publication number
WO2022145335A1
WO2022145335A1 PCT/JP2021/047845 JP2021047845W WO2022145335A1 WO 2022145335 A1 WO2022145335 A1 WO 2022145335A1 JP 2021047845 W JP2021047845 W JP 2021047845W WO 2022145335 A1 WO2022145335 A1 WO 2022145335A1
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resistor
gas
sensor
signal
filter circuit
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PCT/JP2021/047845
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French (fr)
Japanese (ja)
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利彦 紀和
啓二 塚田
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国立大学法人 岡山大学
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Publication of WO2022145335A1 publication Critical patent/WO2022145335A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid

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  • the present invention relates to a gas sensor and a circuit for the sensor.
  • sensors for detecting gas various response principles such as sensors that utilize changes in electrical conductivity in metal oxide semiconductors, sensors that utilize changes in the work function of catalytic metals, and sensors that utilize temperature changes due to catalytic reaction heat. Sensors using the above have been reported.
  • the metal oxidant when the metal oxidant comes into contact with the gas, the oxygen of the metal oxidant is reduced and the conductivity of the metal oxidant changes.
  • the gas concentration can be detected by detecting the change as the change in resistance.
  • a metal oxide semiconductor is sintered on a platinum wire that acts as a heater to form a sensor element, and the gas concentration can be detected by detecting the resistance change of the sensor element with a bridge circuit.
  • a hot wire type semiconductor type gas sensor is known.
  • a gas sensor using a field effect transistor As a gas sensor that has good mass productivity and operates near room temperature, a gas sensor using a field effect transistor is known.
  • a catalyst metal is used as a gate metal on the insulating film of the field-effect transistor which is a sensor element (see, for example, Patent Document 1 and Non-Patent Document 1).
  • the gas to be measured instead of measuring the resistance change and electromotive force change of the sensor element, causes dissociation adsorption and desorption reaction with the catalyst metal of the gate metal, so that the catalyst metal
  • the change in the work function that occurs in is measured by an electric field effect transistor.
  • the field-effect transistor has a very high gate input impedance and a low output impedance between the drain and source, which is the output, that is, it is an impedance conversion element and is a catalyst metal that changes depending on the gas concentration. It is possible to measure weak potential changes.
  • Non-Patent Document 2 As a gas sensor for detecting a temperature change due to an exothermic reaction of a catalyst metal with respect to gas, a sensor element having a platinum film on a thermocouple has been reported (see, for example, Non-Patent Document 2), and the exotherm of platinum in this case is reported. A method of converting heat generated by a reaction into an electric signal by a thermoelectric conversion circuit and detecting it has been reported (see, for example, Patent Document 2).
  • a gas sensor for detecting hydrogen gas a gas sensor using a metal hydride in which hydrogen gas is stabilized in a metal lattice has been proposed (see, for example, Patent Document 3 and Non-Patent Document 3). It is known that in this metal hydride, structural changes occur due to occlusion of hydrogen gas, and the electrical resistance changes, and hydrogen gas can be detected by detecting this resistance change. In particular, metal hydrides have the advantage of being easy to miniaturize because they function even in a very thin thin film state of about several tens of nm.
  • the detection sensitivity is usually improved by detecting the resistance change using a bridge circuit.
  • the present inventor has conducted research and development to make a gas sensor that can easily cope with the increase in the number of sensors and can adjust the sensitivity, and has come to the present invention.
  • the gas sensor of the present invention is a gas sensor that detects a change in gas concentration in a measurement object by detecting a change in the resistance of a resistor that comes into contact with the object to be measured, and the first resistor has a different resistance value.
  • An input signal generator that is configured to connect a resistor and a second resistor in series, and inputs an AC voltage signal adjusted to a predetermined frequency to the connected resistor, and the above. It has a filter circuit that is connected to a resistor and passes or shields a signal of a predetermined AC voltage, and measures from the change in amplitude or phase of the signal output from the filter circuit corresponding to the fluctuation of the resistance of the resistor. It detects changes in the concentration of the target gas. This makes it possible to adjust the detection sensitivity by adjusting the frequency of the input signal and the resistance value of each resistor with no load.
  • the gas sensor of the present invention is also characterized in the following points.
  • the first resistor and the second resistor are formed of a platinum thin film.
  • the filter circuit is a notch filter circuit in which a first resistor and a second resistor are connected in series, and the conductivity of the first resistor and the second resistor is gas. It changes according to the concentration.
  • a plurality of the resistors having the first resistor and the second resistor connected in series are arranged, and an AC signal is simultaneously input to each resistor from the input signal generation unit to display a plurality of measurement targets. It is characterized by detecting a change in gas concentration in an object. This enables multi-point measurement by one sensor unit having a plurality of detection ends, and makes it possible to adjust the detection sensitivity for each point. In addition, it is possible to perform multi-point measurement that is less susceptible to transmission loss of detection signals and disturbance.
  • the sensor circuit of the present invention is a sensor circuit capable of detecting the state of an object to be measured by causing a change in the amplitude or phase of an input AC voltage signal, and is a first resistor and a second resistor. It is composed of a notch filter circuit in which resistors are connected in series, and the conductivity of the first resistor and the second resistor is changed according to the state of the object to be measured.
  • the sensor circuit of the present invention is also characterized in the following points.
  • the object to be measured is gas, and the state of the object to be measured is the concentration of gas.
  • the first resistor and the second resistor are formed of a platinum thin film.
  • An adjustment means for adjusting the frequency of the input signal shall be provided.
  • the change generated in the measurement target is measured by detecting the change in amplitude or phase generated in the signal of the input AC voltage, unlike the conventional detection of the resistance value change,
  • the inspection sensitivity can be optimized by adjusting the detection frequency, and multi-point measurement can be enabled by making the detection frequencies different from each other.
  • the gas sensor and sensor circuit of the present invention do not measure physical quantities such as conductivity or electrical resistance, but input a signal of a predetermined AC voltage to the detection unit and output from the detection unit according to a change in the state of the object to be measured. It is detected as a change in amplitude or phase that occurs in the signal.
  • the detection unit is a gas sensor that detects changes in the gas concentration in the object to be measured by detecting changes in the resistance of the resistor in contact with the object to be measured, and the resistors have different resistance values.
  • An input signal generator which comprises a configuration in which a first resistor and a second resistor are connected in series, and inputs an AC voltage signal adjusted to a predetermined frequency to the connected resistor.
  • a filter circuit connected to the resistor and passing or blocking a signal of a predetermined AC voltage, in particular, the filter circuit is a notch having a first resistance and a second resistor connected in series. It utilizes the characteristics of the filter circuit.
  • a sensor unit 10 configured by a notch filter circuit, an input signal generation unit 20 for inputting a predetermined AC voltage signal to the sensor unit 10, and a sensor unit 10
  • the output signal detection unit 30 that detects the amplitude and phase of the output signal of the above, and the analysis unit 40 that controls the input signal generation unit 20 and the output signal detection unit 30 and specifies the concentration of the gas detected by the sensor unit 10. It is equipped.
  • the input signal generation unit 20 may be controlled by the analysis unit 40 to generate and output a signal having a predetermined AC voltage.
  • the output signal detection unit 30 may detect the amplitude information and the phase information from the output signal of the sensor unit 10 and can input the amplitude information signal and the phase information signal to the analysis unit 40.
  • the output signal detection unit 30 may be integrally configured with the analysis unit 40. In that case, the analysis unit 40 detects the amplitude information and the phase information from the output signal of the sensor unit 10.
  • the analysis unit 40 is a personal computer in which a predetermined program is installed, and the gas in the vicinity of the sensor unit 10 is described from the amplitude information and the phase information obtained from the output signal of the sensor unit 10. It is possible to detect changes in concentration.
  • the sensor unit 10 is a so-called notch filter circuit.
  • the notch filter circuit is a first capacitor connected in series with a first wiring 11 having a first resistor R1 and a second resistor R2 connected in series between the input terminal 15 and the output terminal 16.
  • C1 and the second wiring 12 having the second capacitor C2 are connected in parallel.
  • a first grounded wire 13 having one end grounded is connected between the first resistor R1 and the second resistor R2, and a third capacitor C3 is connected in the middle of the first grounded wire 13.
  • a second grounded wiring 14 having one end grounded is connected between the first capacitor C1 and the second capacitor C2, and a third resistor is connected in the middle of the second grounded wiring 14.
  • the body R3 is provided.
  • the AC voltage of a predetermined frequency is adjusted by adjusting the resistance values of the first to third resistors R1, R2, and R3 and the capacitances of the first to third capacitors C1, C2, and C3. It is known that it is possible to pass or block the signal of.
  • the first resistor R1 and the second resistor R2 are formed of a platinum thin film whose conductivity changes according to the gas concentration.
  • the first resistor R1 and the second resistor R2 formed of the platinum thin film are formed by providing a platinum thin film having a predetermined shape on a glass substrate having an adhesive metal thin film on the surface thereof, respectively. It is R2.
  • a titanium film is desirable as the metal thin film for adhesion, and a titanium film is formed on the upper surface of an insulator substrate such as a glass substrate by sputtering or the like, and a platinum thin film is formed on the upper surface of the titanium film by sputtering or the like.
  • a metal thin film such as chromium or a titanium nitride thin film which is a nitride of titanium can be used.
  • the shapes of the first resistor R1 and the second resistor R2 can be patterned into a desired shape by using an appropriate resist film or by performing an etching operation after forming a platinum thin film.
  • the platinum thin film be as thin as possible, and a film thickness of several nm is sufficient. Further, it is desirable that the platinum thin film has a large surface area, and a porous glass layer or the like may be provided on the surface of the glass substrate to form an uneven shape on the surface, and the titanium film and the platinum thin film may be sequentially formed.
  • the sensor unit 10 in which the first resistor R1 and the second resistor R2 are formed of a platinum thin film is first when the first resistor R1 and the second resistor R2 come into contact with each other and a predetermined gas.
  • the conductivity of the resistor R1 and the second resistor R2 changes, respectively, and in the sensor unit 10 which is the notch filter circuit, the frequency of the signal shielded by the notch filter circuit or the frequency of the signal to pass through changes.
  • an input AC voltage signal set to 10 kHz / 0.15 Vp-p is input from the input signal generation unit 20 to the sensor unit 10, and the amplitude signal and phase signal of the output signal of the sensor unit 10 are shown in FIG.
  • the resistance change when a direct current of 1 mA was input to the sensor unit 10 was also measured.
  • the gas in contact with the first resistor R1 and the second resistor R2 was 1% hydrogen gas.
  • the change in resistance value is about -1% or less due to contact with hydrogen gas, whereas the change in amplitude signal is about -2.5%, which is about 3. It can be seen that the sensitivity is doubled, and the change in the phase signal is about -23%, which is close to 25 times the sensitivity.
  • FIG. 3 shows a change in the phase signal when the frequency of the input signal is changed in a state where 1% hydrogen gas and air are flowing.
  • the rate of change of the phase signal changes significantly in a specific region as shown in FIG. 3D (in the example of the figure, it has a peak in the vicinity of 10 kHz.
  • the sensitivity can be adjusted by adjusting the frequency of the signal input from the input signal generation unit 20 to the sensor unit 10. If the amplitude of the output signal is A and the phase is ⁇ , then dA / df and d ⁇ / The detection sensitivity can be maximized by setting the frequency f at which df becomes the largest.
  • a plurality of resistors having a first resistor and a second resistor connected in series are arranged, and an AC signal is simultaneously input to each resistor from an input signal generation unit to form a plurality of resistors. It detects changes in gas concentration in the object to be measured. That is, as shown in FIG. 4, a plurality of sensor units 10-1, 10-2, 10-3 are connected in series, and a third resistor of each sensor unit 10-1, 10-2, 10-3 is connected. By adjusting R3, the first capacitor C1, the second capacitor C2, and the third capacitor C3, the frequency of the maximum detection sensitivity can be made different in each sensor unit 10-1, 10-2, 10-3, so that a plurality of sensors can be detected.
  • Measurement by each sensor unit 10-1, 10-2, 10-3 can also be performed by a set of input signal generation unit 20, output signal detection unit 30, and analysis unit 40.
  • the third resistor R3, the first capacitor C1, the second capacitor C2, and the third capacitor C3 are adjusting means for adjusting the frequency of the signal used for detection.
  • the capacity of the first capacitor C1 of each sensor unit 10-1,10-2,10-3 is 4.7 ⁇ F
  • the capacity of the second capacitor C2 is 4.7 ⁇ F
  • the resistance value of the first resistor R1 of -3 is 39.2 ⁇ and the resistance value of the second resistor R2 is 28.4 ⁇
  • the resistance value of the third resistor R3 of the first sensor unit 10-1 is 16 ⁇ .
  • the capacity of the 3rd capacitor is 10 ⁇ F
  • the resistance value of the 3rd resistor R3 of the 2nd sensor unit 10-2 is 16 ⁇
  • the capacity of the 3rd capacitor is 1 ⁇ F
  • the first sensor unit 10-1 has the maximum detection sensitivity at 1kHz
  • the second sensor unit 10-2 has the maximum detection sensitivity at 10kHz
  • the third sensor unit 10-3 has a maximum detection sensitivity, and can be configured to have a maximum detection sensitivity at 500 kHz.
  • the input signal generation unit 20 is an adjusting means for adjusting the frequency of the signal by sweeping the frequency of the input AC voltage.
  • the present invention can be used for a gas sensor.

Abstract

Provided are: a gas sensor that readily handles an increase in the number of sensors and can be adjusted for sensitivity; and a sensor circuit therefor.　The present invention is a gas sensor in which a filter circuit, that allows the passage of or blocks a prescribed AC voltage signal, serves as a sensor circuit, the gas sensor being equipped with said filter circuit, and the gas sensor being configured such that changes in the concentration of a gas being measured are detected from amplitude or phase changes in a signal outputted from the filter circuit. The gas sensor is configured such that the filter circuit is a notch/filter circuit that connects a first resistor (R1) and a second resistor (R2) in series, and the conductivity of the first resistor (R1) and second resistor (R2) change according to the concentration of the gas.

Description

ガスセンサ及びセンサ用回路Gas sensor and sensor circuit
　本発明は、ガスセンサ及びセンサ用回路に関する。 The present invention relates to a gas sensor and a circuit for the sensor.
　ガスを検知するセンサとして、金属酸化物半導体での電気伝導度変化を利用したセンサ、触媒金属の仕事関数変化を利用したセンサ、あるいは触媒反応熱による温度変化を利用したセンサ等の様々な応答原理を利用したセンサが報告されている。 As sensors for detecting gas, various response principles such as sensors that utilize changes in electrical conductivity in metal oxide semiconductors, sensors that utilize changes in the work function of catalytic metals, and sensors that utilize temperature changes due to catalytic reaction heat. Sensors using the above have been reported.
　例えば半導体特性を有する金属酸化体（SnO2）を用いたガスセンサでは、金属酸化体がガスに触れることで金属酸化体の酸素が還元され、金属酸化体の導電性が変化し、この導電性の変化を抵抗の変化として検出することでガス濃度を検出可能としている。 For example, in a gas sensor using a metal oxidant (SnO 2 ) having semiconductor characteristics, when the metal oxidant comes into contact with the gas, the oxygen of the metal oxidant is reduced and the conductivity of the metal oxidant changes. The gas concentration can be detected by detecting the change as the change in resistance.
　また、同様の原理を用いたガスセンサとして、ヒーターの役割をする白金線に金属酸化物半導体を焼結してセンサ素子とし、ブリッジ回路でセンサ素子の抵抗変化を検出することでガス濃度を検出可能とした熱線型半導体式のガスセンサが知られている。 In addition, as a gas sensor using the same principle, a metal oxide semiconductor is sintered on a platinum wire that acts as a heater to form a sensor element, and the gas concentration can be detected by detecting the resistance change of the sensor element with a bridge circuit. A hot wire type semiconductor type gas sensor is known.
　また、量産性が良く、室温近くで動作するガスセンサとして、電界効果型トランジスタを利用したガスセンサが知られている。このガスセンサでは、センサ素子である電界効果型トランジスタの絶縁膜の上にゲート金属として触媒金属を用いている（たとえば、特許文献１、及び非特許文献１参照）。 Further, as a gas sensor that has good mass productivity and operates near room temperature, a gas sensor using a field effect transistor is known. In this gas sensor, a catalyst metal is used as a gate metal on the insulating film of the field-effect transistor which is a sensor element (see, for example, Patent Document 1 and Non-Patent Document 1).
　このような電界効果型トランジスタを用いたガスセンサでは、センサ素子の抵抗変化や起電力変化を測定するのでなく、測定対象のガスがゲート金属の触媒金属と解離吸着、脱着反応を起こすことで触媒金属に生じる仕事関数の変化を、電界効果型トランジスタによって計測している。なお、この場合の電界効果型トランジスタは、ゲートの入力インピーダンスが非常に高く、出力であるドレイン・ソース間での出力インピーダンスが低い、つまりインピーダンス変換素子であり、ガスの濃度によって変化する触媒金属の微弱な電位変化を計測可能となっている。 In a gas sensor using such an electric field effect transistor, instead of measuring the resistance change and electromotive force change of the sensor element, the gas to be measured causes dissociation adsorption and desorption reaction with the catalyst metal of the gate metal, so that the catalyst metal The change in the work function that occurs in is measured by an electric field effect transistor. In this case, the field-effect transistor has a very high gate input impedance and a low output impedance between the drain and source, which is the output, that is, it is an impedance conversion element and is a catalyst metal that changes depending on the gas concentration. It is possible to measure weak potential changes.
　また、ガスに対する触媒金属の発熱反応による温度変化を検出するガスセンサとして、熱電対上に白金皮膜を設けたセンサ素子が報告されており（たとえば、非特許文献２参照）、この場合の白金の発熱反応により生じた熱を熱電変換回路により電気信号に変換して検出する方法が報告されている（たとえば、特許文献２参照）。 Further, as a gas sensor for detecting a temperature change due to an exothermic reaction of a catalyst metal with respect to gas, a sensor element having a platinum film on a thermocouple has been reported (see, for example, Non-Patent Document 2), and the exotherm of platinum in this case is reported. A method of converting heat generated by a reaction into an electric signal by a thermoelectric conversion circuit and detecting it has been reported (see, for example, Patent Document 2).
　あるいは、水素ガスを検出するガスセンサとして、水素ガスが金属格子中において安定化される金属水素化物を利用するガスセンサが提案されている（たとえば、特許文献３、及び非特許文献３参照）。この金属水素化物では、水素ガスの吸蔵によって構造変化が生じ、電気抵抗が変化することが知られており、この抵抗変化を検出することで水素ガスを検出可能としている。特に、金属水素化物は、数10nm程度の非常に薄い薄膜状態であっても機能するため、小型化しやすいという利点がある。 Alternatively, as a gas sensor for detecting hydrogen gas, a gas sensor using a metal hydride in which hydrogen gas is stabilized in a metal lattice has been proposed (see, for example, Patent Document 3 and Non-Patent Document 3). It is known that in this metal hydride, structural changes occur due to occlusion of hydrogen gas, and the electrical resistance changes, and hydrogen gas can be detected by detecting this resistance change. In particular, metal hydrides have the advantage of being easy to miniaturize because they function even in a very thin thin film state of about several tens of nm.
特開２０１０－０６６２３４号公報Japanese Unexamined Patent Publication No. 2010-066234 特開２００７－０６４８６５号公報JP-A-2007-064865 特開２０１６－０７５５９７号公報Japanese Unexamined Patent Publication No. 2016-075597
　上述したうちの抵抗変化型のセンサでは、通常、ブリッジ回路を用いて抵抗変化を検出することで、検出感度を向上させている。 Of the above-mentioned resistance change type sensors, the detection sensitivity is usually improved by detecting the resistance change using a bridge circuit.
　そのため、ブリッジ回路の構成が決定された後には、感度の最適化作業や調整作業を行うことが困難であり、特に、感度低下が生じた場合の補正が困難であり、通常では取り替え作業で対応するしかなかった。 Therefore, after the configuration of the bridge circuit is decided, it is difficult to perform the sensitivity optimization work and the adjustment work, and in particular, it is difficult to correct when the sensitivity is lowered, and it is usually dealt with by the replacement work. I had no choice but to do it.
　さらに、複数のガスセンサを備えた装置とした場合には、センサごとに検出回路を設ける必要があり、センサの数に比例して回路規模が大きくなるという問題もあった。 Furthermore, in the case of a device equipped with a plurality of gas sensors, it is necessary to provide a detection circuit for each sensor, and there is also a problem that the circuit scale increases in proportion to the number of sensors.
　本発明者は、このような現状を鑑み多センサ化に対応しやすく、また感度調整が可能なガスセンサとすべく研究開発を行い、本発明を成すに至ったものである。 In view of this situation, the present inventor has conducted research and development to make a gas sensor that can easily cope with the increase in the number of sensors and can adjust the sensitivity, and has come to the present invention.
　本発明のガスセンサは、計測対象物と接触する抵抗体の抵抗の変動を検出することで計測対象物中のガス濃度の変化を検出するガスセンサであって、前記抵抗体が抵抗値の異なる第１の抵抗体と第２の抵抗体を直列に接続している構成からなり、接続された前記抵抗体に対して所定の周波数に調整された交流電圧の信号を入力する入力信号生成部、および前記抵抗体に接続され、所定の交流電圧の信号を通過あるいは遮蔽するフィルタ回路を有し、前記抵抗体の抵抗の変動に対応した、前記フィルタ回路から出力される信号の振幅または位相の変化から計測対象のガスの濃度変化を検出するものである。
　これにより、入力信号の周波数・各抵抗体の無負荷での抵抗値を調整することによって検出感度の調整が可能となる。 The gas sensor of the present invention is a gas sensor that detects a change in gas concentration in a measurement object by detecting a change in the resistance of a resistor that comes into contact with the object to be measured, and the first resistor has a different resistance value. An input signal generator that is configured to connect a resistor and a second resistor in series, and inputs an AC voltage signal adjusted to a predetermined frequency to the connected resistor, and the above. It has a filter circuit that is connected to a resistor and passes or shields a signal of a predetermined AC voltage, and measures from the change in amplitude or phase of the signal output from the filter circuit corresponding to the fluctuation of the resistance of the resistor. It detects changes in the concentration of the target gas.
This makes it possible to adjust the detection sensitivity by adjusting the frequency of the input signal and the resistance value of each resistor with no load.
　さらに、本発明のガスセンサでは、以下の点にも特徴を有するものである。
（１）第１の抵抗体及び第２の抵抗体を白金薄膜で形成していること。
（２）フィルタ回路は、第１の抵抗体と第２の抵抗体を直列に接続しているノッチ・フィルタ回路であって、第１の抵抗体及び第２の抵抗体の導電率がガスの濃度に応じて変化すること。
　また、直列に接続された第１の抵抗体と第２の抵抗体を有する前記抵抗体が複数配設され、各抵抗体に前記入力信号生成部から同時に交流信号を入力し、複数の計測対象物中のガス濃度の変化を検出することを特徴とする。
　これにより、複数検出端を有する１つのセンサユニットによる多点測定が可能となり、各点ごとの検出感度調整が可能となる。また、検出信号の送信ロスや外乱影響を受けにくい多点測定が可能となる。 Further, the gas sensor of the present invention is also characterized in the following points.
(1) The first resistor and the second resistor are formed of a platinum thin film.
(2) The filter circuit is a notch filter circuit in which a first resistor and a second resistor are connected in series, and the conductivity of the first resistor and the second resistor is gas. It changes according to the concentration.
Further, a plurality of the resistors having the first resistor and the second resistor connected in series are arranged, and an AC signal is simultaneously input to each resistor from the input signal generation unit to display a plurality of measurement targets. It is characterized by detecting a change in gas concentration in an object.
This enables multi-point measurement by one sensor unit having a plurality of detection ends, and makes it possible to adjust the detection sensitivity for each point. In addition, it is possible to perform multi-point measurement that is less susceptible to transmission loss of detection signals and disturbance.
　本発明のセンサ回路は、入力された交流電圧の信号の振幅または位相に変化を生じさせることで計測対象物の状態を検出可能とするセンサ回路であって、第１の抵抗体と第２の抵抗体を直列に接続しているノッチ・フィルタ回路で構成し、第１の抵抗体及び第２の抵抗体の導電率を計測対象物の状態に応じて変化させているものである。 The sensor circuit of the present invention is a sensor circuit capable of detecting the state of an object to be measured by causing a change in the amplitude or phase of an input AC voltage signal, and is a first resistor and a second resistor. It is composed of a notch filter circuit in which resistors are connected in series, and the conductivity of the first resistor and the second resistor is changed according to the state of the object to be measured.
　さらに、本発明のセンサ回路では、以下の点にも特徴を有するものである。
（１）計測対象物はガスであって、計測対象物の状態はガスの濃度であること。
（２）第１の抵抗体及び第２の抵抗体を白金薄膜で形成していること。
（３）入力される信号の周波数を調整する調整手段を設けていること。 Further, the sensor circuit of the present invention is also characterized in the following points.
(1) The object to be measured is gas, and the state of the object to be measured is the concentration of gas.
(2) The first resistor and the second resistor are formed of a platinum thin film.
(3) An adjustment means for adjusting the frequency of the input signal shall be provided.
　本発明のガスセンサ及びセンサ回路では、入力した交流電圧の信号に生じた振幅または位相の変化を検出することによって計測対象に生じた変化を計測することから、従来の抵抗値変化の検出と異なり、検出する周波数を調整することで検査感度を最適化したり、検出する周波数を互いに異ならせることで多点計測を可能としたりすることができる。 In the gas sensor and the sensor circuit of the present invention, since the change generated in the measurement target is measured by detecting the change in amplitude or phase generated in the signal of the input AC voltage, unlike the conventional detection of the resistance value change, The inspection sensitivity can be optimized by adjusting the detection frequency, and multi-point measurement can be enabled by making the detection frequencies different from each other.
本発明に係るガスセンサの構成説明図である。It is a block diagram of the gas sensor which concerns on this invention. 本発明に係るガスセンサを用いた１％水素ガスの検出試験の結果のグラフである。It is a graph of the result of the detection test of 1% hydrogen gas using the gas sensor which concerns on this invention. 出力信号の検出周波数による依存性を示すグラフである。It is a graph which shows the dependence by the detection frequency of an output signal. 本発明に係るガスセンサの変容例の説明図である。It is explanatory drawing of the transformation example of the gas sensor which concerns on this invention. 本発明に係るガスセンサの変容例の説明図である。It is explanatory drawing of the transformation example of the gas sensor which concerns on this invention.
　本発明のガスセンサ及びセンサ回路は、導電率あるいは電気抵抗等の物理量を計測するのではなく、検出部に所定の交流電圧の信号を入力し、計測対象物の状態の変化によって検出部からの出力信号に生じる振幅または位相の変化として検出しているものである。 The gas sensor and sensor circuit of the present invention do not measure physical quantities such as conductivity or electrical resistance, but input a signal of a predetermined AC voltage to the detection unit and output from the detection unit according to a change in the state of the object to be measured. It is detected as a change in amplitude or phase that occurs in the signal.
　本発明では、検出部は、計測対象物と接触する抵抗体の抵抗の変動を検出することで計測対象物中のガス濃度の変化を検出するガスセンサであって、前記抵抗体が抵抗値の異なる第１の抵抗体と第２の抵抗体を直列に接続している構成からなり、接続された前記抵抗体に対して所定の周波数に調整された交流電圧の信号を入力する入力信号生成部、および前記抵抗体に接続され、所定の交流電圧の信号を通過あるいは遮蔽するフィルタ回路で構成しており、特に、フィルタ回路は、直列に接続した第１抵抗体と第２抵抗体を有するノッチ・フィルタ回路の特性を利用するものである。 In the present invention, the detection unit is a gas sensor that detects changes in the gas concentration in the object to be measured by detecting changes in the resistance of the resistor in contact with the object to be measured, and the resistors have different resistance values. An input signal generator, which comprises a configuration in which a first resistor and a second resistor are connected in series, and inputs an AC voltage signal adjusted to a predetermined frequency to the connected resistor. And a filter circuit connected to the resistor and passing or blocking a signal of a predetermined AC voltage, in particular, the filter circuit is a notch having a first resistance and a second resistor connected in series. It utilizes the characteristics of the filter circuit.
　すなわち、本発明のガスセンサでは、図１に示すように、ノッチ・フィルタ回路で構成したセンサ部10と、このセンサ部10に所定の交流電圧信号を入力する入力信号生成部20と、センサ部10の出力信号の振幅及び位相を検出する出力信号検出部30と、入力信号生成部20と出力信号検出部30とを制御するとともにセンサ部10で検出したガスの濃度を特定する解析部40とを具備している。 That is, in the gas sensor of the present invention, as shown in FIG. 1, a sensor unit 10 configured by a notch filter circuit, an input signal generation unit 20 for inputting a predetermined AC voltage signal to the sensor unit 10, and a sensor unit 10 The output signal detection unit 30 that detects the amplitude and phase of the output signal of the above, and the analysis unit 40 that controls the input signal generation unit 20 and the output signal detection unit 30 and specifies the concentration of the gas detected by the sensor unit 10. It is equipped.
　入力信号生成部20は、解析部40からの制御を受けて、所定の交流電圧の信号を生成して出力可能であればよい。 The input signal generation unit 20 may be controlled by the analysis unit 40 to generate and output a signal having a predetermined AC voltage.
　出力信号検出部30は、センサ部10の出力信号から振幅情報及び位相情報を検出して、振幅情報信号及び位相情報信号として解析部40に入力可能となっていればよい。なお、出力信号検出部30は、解析部40と一体的に構成してもよく、その場合、解析部40でセンサ部10の出力信号から振幅情報及び位相情報を検出する。 The output signal detection unit 30 may detect the amplitude information and the phase information from the output signal of the sensor unit 10 and can input the amplitude information signal and the phase information signal to the analysis unit 40. The output signal detection unit 30 may be integrally configured with the analysis unit 40. In that case, the analysis unit 40 detects the amplitude information and the phase information from the output signal of the sensor unit 10.
　解析部40は、本実施形態では、所定のプログラムがインストールされたパーソナルコンピュータであって、センサ部10の出力信号から得られた振幅情報及び位相情報から後述するようにセンサ部10近傍のガスの濃度変化を検出可能としている。 In the present embodiment, the analysis unit 40 is a personal computer in which a predetermined program is installed, and the gas in the vicinity of the sensor unit 10 is described from the amplitude information and the phase information obtained from the output signal of the sensor unit 10. It is possible to detect changes in concentration.
　センサ部10は、図１に示すように、いわゆるノッチ・フィルタ回路としている。 As shown in FIG. 1, the sensor unit 10 is a so-called notch filter circuit.
　ノッチ・フィルタ回路は、具体的には、入力端子15と出力端子16の間に、直列接続した第１抵抗体R1と第２抵抗体R2を有する第1配線11と、直列接続した第１コンデンサC1と第２コンデンサC2を有する第２配線12とを並列接続している。さらに、第１抵抗体R1と第２抵抗体R2との間には、一方端を接地した第1接地配線13を接続するとともに、この第1接地配線13の中途部には、第３コンデンサC3を設け、また、第１コンデンサC1と第２コンデンサC2との間には、一方端を接地した第２接地配線14を接続するとともに、この第２接地配線14の中途部には、第３抵抗体R3を設けている。 Specifically, the notch filter circuit is a first capacitor connected in series with a first wiring 11 having a first resistor R1 and a second resistor R2 connected in series between the input terminal 15 and the output terminal 16. C1 and the second wiring 12 having the second capacitor C2 are connected in parallel. Further, a first grounded wire 13 having one end grounded is connected between the first resistor R1 and the second resistor R2, and a third capacitor C3 is connected in the middle of the first grounded wire 13. A second grounded wiring 14 having one end grounded is connected between the first capacitor C1 and the second capacitor C2, and a third resistor is connected in the middle of the second grounded wiring 14. The body R3 is provided.
　このようなノッチ・フィルタ回路では、第１～３抵抗体R1,R2,R3の各抵抗値及び第１～３コンデンサC1,C2,C3の各容量を調整することで、所定の周波数の交流電圧の信号を通過可能あるいは遮断可能となっていることが知られている。 In such a notch filter circuit, the AC voltage of a predetermined frequency is adjusted by adjusting the resistance values of the first to third resistors R1, R2, and R3 and the capacitances of the first to third capacitors C1, C2, and C3. It is known that it is possible to pass or block the signal of.
　本発明では、第１抵抗体R1と第２抵抗体R2を、ガスの濃度に報じて導電率が変化する白金薄膜で形成している。 In the present invention, the first resistor R1 and the second resistor R2 are formed of a platinum thin film whose conductivity changes according to the gas concentration.
　本実施形態では、白金薄膜で形成する第１抵抗体R1と第２抵抗体R2は、表面に接着用金属薄膜を設けたガラス基板に所定形状とした白金薄膜を設けて、それぞれ抵抗体R1.R2としている。 In the present embodiment, the first resistor R1 and the second resistor R2 formed of the platinum thin film are formed by providing a platinum thin film having a predetermined shape on a glass substrate having an adhesive metal thin film on the surface thereof, respectively. It is R2.
　接着用金属薄膜としては、チタン膜が望ましく、ガラス基板等の絶縁体基板の上面にスパッタリング等によってチタン膜を形成し、このチタン膜の上面にスパッタリング等によって白金薄膜を形成している。チタン膜の代わりにクロム等の金属薄膜や、チタンの窒化物である窒化チタン薄膜等を用いることができる。第１抵抗体R1と第２抵抗体R2の形状は、適宜のレジスト膜を用いたり、あるいは白金薄膜の形成後にエッチング作業を行ったりすることで、所望の形状にパターンニングすることができる。 A titanium film is desirable as the metal thin film for adhesion, and a titanium film is formed on the upper surface of an insulator substrate such as a glass substrate by sputtering or the like, and a platinum thin film is formed on the upper surface of the titanium film by sputtering or the like. Instead of the titanium film, a metal thin film such as chromium or a titanium nitride thin film which is a nitride of titanium can be used. The shapes of the first resistor R1 and the second resistor R2 can be patterned into a desired shape by using an appropriate resist film or by performing an etching operation after forming a platinum thin film.
　白金薄膜は、できるだけ薄いことが望ましく、数nmの膜厚で十分である。また、白金薄膜は表面積が大きい方が望ましく、ガラス基板の表面に多孔質ガラス層等を設けて表面に凹凸形状を形成して、チタン膜及び白金薄膜を順次形成してもよい。 It is desirable that the platinum thin film be as thin as possible, and a film thickness of several nm is sufficient. Further, it is desirable that the platinum thin film has a large surface area, and a porous glass layer or the like may be provided on the surface of the glass substrate to form an uneven shape on the surface, and the titanium film and the platinum thin film may be sequentially formed.
　このように、第１抵抗体R1と第２抵抗体R2とを白金薄膜で形成したセンサ部10は、第１抵抗体R1及び第２抵抗体R2と所定のガスがそれぞれ接触することで第１抵抗体R1及び第２抵抗体R2の導電率がそれぞれ変化し、ノッチ・フィルタ回路であるセンサ部10では、ノッチ・フィルタ回路が遮蔽する信号の周波数、あるいは通過させる信号の周波数が変化する。 In this way, the sensor unit 10 in which the first resistor R1 and the second resistor R2 are formed of a platinum thin film is first when the first resistor R1 and the second resistor R2 come into contact with each other and a predetermined gas. The conductivity of the resistor R1 and the second resistor R2 changes, respectively, and in the sensor unit 10 which is the notch filter circuit, the frequency of the signal shielded by the notch filter circuit or the frequency of the signal to pass through changes.
　ここで、入力信号生成部20から10kHz/0.15Vp-pとした入力交流電圧信号をセンサ部10に入力し、センサ部10かの出力信号の振幅信号と位相信号を図２に示す。また、比較として直流電流1mAをセンサ部10に入力した場合の抵抗変化も計測した。第１抵抗体R1及び第２抵抗体R2に接触させるガスは１％の水素ガスとした。 Here, an input AC voltage signal set to 10 kHz / 0.15 Vp-p is input from the input signal generation unit 20 to the sensor unit 10, and the amplitude signal and phase signal of the output signal of the sensor unit 10 are shown in FIG. For comparison, the resistance change when a direct current of 1 mA was input to the sensor unit 10 was also measured. The gas in contact with the first resistor R1 and the second resistor R2 was 1% hydrogen gas.
　図２に示すように、センサ部10では、水素ガスと接触することで抵抗値変化は約－１％弱であるのに対し、振幅信号の変化では約－２．５％であって約３倍の感度があり、位相信号の変化では約－２３％であって約２５倍近い感度があることがわかる。 As shown in FIG. 2, in the sensor unit 10, the change in resistance value is about -1% or less due to contact with hydrogen gas, whereas the change in amplitude signal is about -2.5%, which is about 3. It can be seen that the sensitivity is doubled, and the change in the phase signal is about -23%, which is close to 25 times the sensitivity.
　また、このように信号変化の大きい位相信号であっても、図３に示すように入力信号生成部20からセンサ部10に入力する信号の周波数が異なると、検出感度が大きく異なる。ここで、１％水素ガスを空気と２回交互に流しており、図３（ａ）は10kHzの入力信号、図３（ｂ）は20kHzの入力信号としている。
　図３（ｃ）は、１％水素ガスと空気を流した状態において、入力する信号の周波数を変化させたときの位相信号の変化を示す。このとき、位相信号の変化率は、図３（ｄ）のように特定領域において大きく変化する（図の例では10kHz近傍においてピークを有する。
　図示しないが、振幅信号でも同様である。 Further, even for a phase signal having a large signal change as described above, if the frequencies of the signals input from the input signal generation unit 20 to the sensor unit 10 are different as shown in FIG. 3, the detection sensitivity is significantly different. Here, 1% hydrogen gas is alternately flowed with air twice, and FIG. 3A shows an input signal of 10 kHz and FIG. 3B shows an input signal of 20 kHz.
FIG. 3C shows a change in the phase signal when the frequency of the input signal is changed in a state where 1% hydrogen gas and air are flowing. At this time, the rate of change of the phase signal changes significantly in a specific region as shown in FIG. 3D (in the example of the figure, it has a peak in the vicinity of 10 kHz.
Although not shown, the same applies to the amplitude signal.
　すなわち、入力信号生成部20からセンサ部10に入力する信号の周波数を調整することで感度を調整できることを示しており、出力信号の振幅をＡ、位相をθとすると、dA/df、dθ/dfが最も大きくなる周波数fとすることで検出感度を最大とすることができる。 That is, it is shown that the sensitivity can be adjusted by adjusting the frequency of the signal input from the input signal generation unit 20 to the sensor unit 10. If the amplitude of the output signal is A and the phase is θ, then dA / df and dθ / The detection sensitivity can be maximized by setting the frequency f at which df becomes the largest.
　また、本発明は、直列に接続された第１の抵抗体と第２の抵抗体を有する抵抗体が複数配設され、各抵抗体に入力信号生成部から同時に交流信号を入力し、複数の計測対象物中のガス濃度の変化を検出するものである。すなわち、図４に示すように、複数のセンサ部10-1,10-2,10-3を直列に接続するとともに、各センサ部10-1,10-2,10-3の第３抵抗体R3、第１コンデンサC1、第２コンデンサC2及び第３コンデンサC3を調整することで、最大検出感度の周波数を各センサ部10-1,10-2,10-3で異ならせることで、複数の各センサ部10-1,10-2,10-3での計測を1組の入力信号生成部20、出力信号検出部30及び解析部40で行うこともできる。第３抵抗体R3、第１コンデンサC1、第２コンデンサC2及び第３コンデンサC3は、検出に用いる信号の周波数を調整する調整手段となっている。 Further, in the present invention, a plurality of resistors having a first resistor and a second resistor connected in series are arranged, and an AC signal is simultaneously input to each resistor from an input signal generation unit to form a plurality of resistors. It detects changes in gas concentration in the object to be measured. That is, as shown in FIG. 4, a plurality of sensor units 10-1, 10-2, 10-3 are connected in series, and a third resistor of each sensor unit 10-1, 10-2, 10-3 is connected. By adjusting R3, the first capacitor C1, the second capacitor C2, and the third capacitor C3, the frequency of the maximum detection sensitivity can be made different in each sensor unit 10-1, 10-2, 10-3, so that a plurality of sensors can be detected. Measurement by each sensor unit 10-1, 10-2, 10-3 can also be performed by a set of input signal generation unit 20, output signal detection unit 30, and analysis unit 40. The third resistor R3, the first capacitor C1, the second capacitor C2, and the third capacitor C3 are adjusting means for adjusting the frequency of the signal used for detection.
　例えば、各センサ部10-1,10-2,10-3の第１コンデンサC1の容量を4.7μＦ、第２コンデンサC2の容量を4.7μＦとし、各センサ部10-1,10-2,10-3の第１抵抗体R1の抵抗値が39.2Ω、第２抵抗体R2の抵抗値が28.4Ωであった場合、第１センサ部10-1の第３抵抗体R3の抵抗値を16Ω、第３コンデンサの容量を10μＦ、第２センサ部10-2の第３抵抗体R3の抵抗値を16Ω、第３コンデンサの容量を1μＦ、第３センサ部10-3の第３抵抗体R3の抵抗値を0.8Ω、第３コンデンサの容量を0.01μＦとすると、図５に示すように、第１センサ部10-1は1kHzに最大検出感度を有し、第２センサ部10-2は10kHzに最大検出感度を有し、第３センサ部10-3は500kHzに最大検出感度を有する構成とすることができる。 For example, the capacity of the first capacitor C1 of each sensor unit 10-1,10-2,10-3 is 4.7 μF, the capacity of the second capacitor C2 is 4.7 μF, and each sensor unit 10-1,10-2,10. When the resistance value of the first resistor R1 of -3 is 39.2Ω and the resistance value of the second resistor R2 is 28.4Ω, the resistance value of the third resistor R3 of the first sensor unit 10-1 is 16Ω. The capacity of the 3rd capacitor is 10μF, the resistance value of the 3rd resistor R3 of the 2nd sensor unit 10-2 is 16Ω, the capacity of the 3rd capacitor is 1μF, and the resistance of the 3rd resistor R3 of the 3rd sensor unit 10-3. Assuming that the value is 0.8Ω and the capacitance of the third capacitor is 0.01μF, as shown in FIG. 5, the first sensor unit 10-1 has the maximum detection sensitivity at 1kHz, and the second sensor unit 10-2 has the maximum detection sensitivity at 10kHz. The third sensor unit 10-3 has a maximum detection sensitivity, and can be configured to have a maximum detection sensitivity at 500 kHz.
　このように、検出周波数を調整することで複数のセンサ部を１組の入力信号生成部20、出力信号検出部30及び解析部40で行うこともでき、多点検出システムあるいはセンサ部の故障を考慮したバックアップシステムを容易に構築することができる。特に、入力信号生成部20は、入力する交流電圧の周波数を掃引することで、信号の周波数を調整する調整手段となっている。 In this way, by adjusting the detection frequency, a plurality of sensor units can be performed by a set of input signal generation unit 20, output signal detection unit 30, and analysis unit 40, and a failure of the multipoint detection system or sensor unit can be performed. A backup system that takes this into consideration can be easily constructed. In particular, the input signal generation unit 20 is an adjusting means for adjusting the frequency of the signal by sweeping the frequency of the input AC voltage.
　本発明は、ガスセンサに利用可能である。 The present invention can be used for a gas sensor.
　10　　センサ部
　10-1　第１センサ部
　10-2　第２センサ部
　10-3　第３センサ部
　11　　第1配線
　12　　第２配線
　13　　第1接地配線
　14　　第２接地配線
　15　　入力端子
　16　　出力端子
　20　　入力信号生成部
　30　　出力信号検出部
　40　　解析部
　R1　　第１抵抗体
　R2　　第２抵抗体
　R3　　第３抵抗体
　C1　　第１コンデンサ
　C2　　第２コンデンサ
　C3　　第３コンデンサ 10 Sensor unit 10-1 1st sensor unit 10-2 2nd sensor unit 10-3 3rd sensor unit 11 1st wiring 12 2nd wiring 13 1st ground wiring 14 2nd ground wiring 15 Input terminal 16 Output terminal 20 Input Signal generation unit 30 Output signal detection unit 40 Analysis unit R1 1st resistor R2 2nd resistor R3 3rd resistor C1 1st capacitor C2 2nd capacitor C3 3rd capacitor

Claims (8)

  1. 　　計測対象物と接触する抵抗体の抵抗の変動を検出することで計測対象物中のガス濃度の変化を検出するガスセンサであって、
    　前記抵抗体が抵抗値の異なる第１の抵抗体と第２の抵抗体を直列に接続している構成からなり、
    　接続された前記抵抗体に対して所定の周波数に調整された交流電圧の信号を入力する入力信号生成部、
    　および前記抵抗体に接続され、所定の交流電圧の信号を通過あるいは遮蔽するフィルタ回路を有し、
    　前記抵抗体の抵抗の変動に対応した、前記フィルタ回路から出力される信号の振幅または位相の変化から計測対象のガスの濃度変化を検出するガスセンサ。     It is a gas sensor that detects changes in the gas concentration in the object to be measured by detecting changes in the resistance of the resistor that comes into contact with the object to be measured.
    The resistor has a configuration in which a first resistor having a different resistance value and a second resistor are connected in series.
    An input signal generator that inputs an AC voltage signal adjusted to a predetermined frequency to the connected resistor.
    And has a filter circuit connected to the resistor and passing or shielding a signal of a predetermined AC voltage.
    A gas sensor that detects a change in the concentration of the gas to be measured from a change in the amplitude or phase of a signal output from the filter circuit corresponding to the fluctuation in the resistance of the resistor.
  2. 　前記第１の抵抗体及び前記第２の抵抗体を白金薄膜で形成している請求項１に記載のガスセンサ。 The gas sensor according to claim 1, wherein the first resistor and the second resistor are formed of a platinum thin film.
  3. 　直列に接続された第１の抵抗体と第２の抵抗体を有する前記抵抗体が複数配設され、各抵抗体に前記入力信号生成部から同時に交流信号を入力し、複数の計測対象物中のガス濃度の変化を検出する請求項1または２記載のガスセンサ。 A plurality of the resistors having the first resistor and the second resistor connected in series are arranged, and an AC signal is simultaneously input to each resistor from the input signal generator to be included in a plurality of measurement objects. The gas sensor according to claim 1 or 2, which detects a change in the gas concentration of.
  4. 　前記フィルタ回路は、第１の抵抗体と第２の抵抗体を直列に接続しているノッチ・フィルタ回路であって、前記第１の抵抗体及び前記第２の抵抗体の導電率が前記ガスの濃度に応じて変化する請求項１～３のいずれか１項に記載のガスセンサ。 The filter circuit is a notch filter circuit in which a first resistor and a second resistor are connected in series, and the conductivity of the first resistor and the second resistor is the gas. The gas sensor according to any one of claims 1 to 3, which changes according to the concentration of the gas sensor.
  5. 　入力された交流電圧の信号の振幅または位相に変化を生じさせることで計測対象物の状態を検出可能とするセンサ回路であって、
    　第１の抵抗体と第２の抵抗体を直列に接続しているノッチ・フィルタ回路で構成し、
    　前記第１の抵抗体及び前記第２の抵抗体の導電率を前記計測対象物の状態に応じて変化させているセンサ回路。     A sensor circuit that can detect the state of an object to be measured by changing the amplitude or phase of the input AC voltage signal.
    It consists of a notch filter circuit that connects the first resistor and the second resistor in series.
    A sensor circuit that changes the conductivity of the first resistor and the second resistor according to the state of the object to be measured.
  6. 　前記計測対象物はガスであって、記計測対象物の状態は前記ガスの濃度である請求項５に記載のセンサ回路。 The sensor circuit according to claim 5, wherein the measurement object is a gas, and the state of the measurement object is the concentration of the gas.
  7. 　前記第１の抵抗体及び前記第２の抵抗体を白金薄膜で形成している請求項５または請求項６に記載のセンサ回路。 The sensor circuit according to claim 5 or 6, wherein the first resistor and the second resistor are formed of a platinum thin film.
  8. 　入力される前記信号の周波数を調整する調整手段を設けている請求項５～７のいずれか１項に記載のセンサ回路。 The sensor circuit according to any one of claims 5 to 7, which is provided with an adjusting means for adjusting the frequency of the input signal.
PCT/JP2021/047845 2020-12-28 2021-12-23 Gas sensor and sensor circuit WO2022145335A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015068802A (en) * 2013-09-30 2015-04-13 国立大学法人 岡山大学 Thin film-type hydrogen gas sensor
JP2016075597A (en) * 2014-10-07 2016-05-12 国立大学法人 岡山大学 Thin-film-type hydrogen gas sensor
JP2019027943A (en) * 2017-07-31 2019-02-21 日立金属株式会社 Gas sensor
US20190204265A1 (en) * 2018-01-04 2019-07-04 Lyten, Inc. Resonant gas sensor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015068802A (en) * 2013-09-30 2015-04-13 国立大学法人 岡山大学 Thin film-type hydrogen gas sensor
JP2016075597A (en) * 2014-10-07 2016-05-12 国立大学法人 岡山大学 Thin-film-type hydrogen gas sensor
JP2019027943A (en) * 2017-07-31 2019-02-21 日立金属株式会社 Gas sensor
US20190204265A1 (en) * 2018-01-04 2019-07-04 Lyten, Inc. Resonant gas sensor

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