JP2007248075A - Gas concentration measuring instrument and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas concentration measuring instrument capable of simply and precisely acquiring an air base at a low cost. <P>SOLUTION: The gas concentration measuring instrument has a combustion control means 11b, which performs control for supplying a current to a catalytic combustion type gas sensor 40 so as to become a combustion temperature for combusting an adsorbed gas to be detected after the supply of the current to the catalytic combustion type gas sensor 40 is stopped so as to adsorb the gas to be detected by the catalytic combustion type gas sensor 40, and a control means 11c for the air base which performs control for supplying the current to the catalytic combustion type gas sensor 40 of a state that the gas to be detected is not adsorbed after the supply of the current to the catalytic combustion type gas sensor 40 is stopped so as to lower the combustion temperature to the circumferential temperature. A concentration calculation means 11a is constituted so as to calculate the concentration of the gas to be detected on the basis of the sensor output at the time of combustion of the catalytic combustion type gas sensor 40 corresponding to the supply of the current due to the combustion control means 11b and the sensor output at the time of the air base of the catalytic combustion type gas sensor 40 corresponding to the supply of the current due to the control means 11c for the air base. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas concentration measuring apparatus and a gas concentration measuring method, and more specifically, measures the concentration of the test gas based on a sensor output output from a catalytic combustion gas sensor in response to an adsorbed test gas. The present invention relates to a gas concentration measuring device and a gas concentration measuring method.

The gas leak alarm device detects a leak of fuel gas and combustible gas to the measurement environment and gives an alarm, and is widely used in kitchens and living rooms regardless of home use or business use. Such a gas leak alarm device is roughly classified into a contact combustion gas sensor and a semiconductor gas leak alarm device having a semiconductor element mainly composed of tin oxide (SnO ₂ ) depending on a detection method. .

  In such an alarm device, as a result of long-term use, even if the air base (baseline) of the output of the detection means such as a catalytic combustion type gas sensor drifts and is necessary, there is a risk of not giving a warning or making a false alarm. Therefore, it was necessary to correct and calibrate periodically. However, since correction and calibration required labor and time, various methods have been proposed in the past in order to save the labor and time.

  For example, in an intermittently driven gas alarm device, the air base is acquired periodically (for example, every few hours) in order to cope with the deterioration of the gas sensor over time, environmental changes, or fluctuations in the air base caused by electrical circuits. In addition, the air base correction operation is performed while comparing with the previous result to compensate the accuracy when the gas is detected (see Patent Document 1).

In addition, as the reference gas for obtaining the air base, high-purity air supplied from a container or clean air obtained through an adsorbent such as activated carbon or zeolite arranged in front of the sensor is used. Concentration measurement is performed by introducing a reference gas into a gas sensor and acquiring an air base, and then switching a gas line to introduce a test gas (see Patent Document 2).
Japanese Patent No. 3183387 JP 2005-180996 A

  However, when using a gas container or an adsorbent for air base calibration, it has been necessary to replace them periodically, and there is a problem that the replacement is costly. In addition, for portable and portable detectors and small analyzers, it requires a container, an adsorbent, and a plurality of flow paths, so that the size of the apparatus is increased, and a complicated system configuration such as a switching operation is required. There was a problem that.

  Therefore, in view of the above-described problems, an object of the present invention is to provide a gas concentration measuring apparatus and a gas concentration measuring method capable of easily and accurately obtaining an air base at a lower cost.

  In order to solve the above problems, the gas concentration measuring apparatus according to claim 1 according to the present invention, as shown in the basic configuration diagram of FIG. 1, is a catalytic combustion type that outputs a sensor output in response to the adsorbed test gas. In a gas concentration measuring device having a gas sensor 40 and a concentration calculation means 11a for measuring the concentration of the test gas based on the sensor output of the catalytic combustion gas sensor 40, the test gas is the catalytic combustion gas sensor 40. After stopping energization of the catalytic combustion type gas sensor 40 so as to be adsorbed to the combustion gas, the combustion control means 11b performs control for energizing the catalytic combustion type gas sensor 40 so as to reach a combustion temperature at which the adsorbed test gas is combusted. And after the energization of the catalytic combustion type gas sensor 40 is stopped so as to decrease from the combustion temperature to the ambient temperature, the test gas is not adsorbed An air-base control unit 11c that controls energization of the catalytic combustion gas sensor 40, and the concentration calculation unit 11a performs combustion of the catalytic combustion gas sensor 40 in response to energization by the combustion control unit 11b. The concentration of the test gas is calculated on the basis of the hour sensor output and the air base hour sensor output of the catalytic combustion gas sensor 40 according to the energization by the air base control means 11c.

  According to a second aspect of the present invention, as shown in the basic configuration diagram of FIG. 1, in the gas concentration measuring device according to the first aspect, the concentration calculating means 11 a includes the continuous combustion sensor output and the air base time. The concentration of the test gas is calculated based on the sensor output.

  In order to solve the above problems, the gas detection method according to claim 3, which is made according to the present invention, measures the concentration of the test gas using a contact combustion type gas sensor that outputs a sensor output sensitive to the adsorbed test gas. In the gas concentration measurement method, after the energization of the catalytic combustion type gas sensor 40 is stopped so that the test gas is adsorbed to the catalytic combustion type gas sensor 40, the temperature becomes a combustion temperature at which the adsorbed test gas is burned. A combustion process for energizing the catalytic combustion gas sensor 40, and after the energization of the catalytic combustion gas sensor 40 is stopped so that the catalytic combustion gas sensor 40 decreases from the combustion temperature to the ambient temperature, An air-base process for energizing the catalytic combustion gas sensor 40 in a state in which the detected gas is not adsorbed, and the catalytic combustion in response to the energization of the combustion process A gas concentration measurement step of measuring the concentration of the test gas based on the sensor output during combustion of the gas sensor 40 and the sensor output during the air base of the catalytic combustion type gas sensor 40 in accordance with the energization of the air base step; It is characterized by having.

  As described above, according to the first and third aspects of the present invention, the energization is stopped so as to decrease to the ambient temperature, the energization is performed so that the test gas is adsorbed and then heated to the combustion temperature. The contact combustion gas sensor outputs the sensor output at the time of combustion, and after energization is stopped so as to decrease from the combustion temperature to the ambient temperature, it is energized and contacted so that the test gas is heated to the combustion temperature without being adsorbed. Since the combustion-type gas sensor outputs the air-base sensor output and detects the gas to be detected based on the combustion-base sensor output and the air-base sensor output, simply controlling the energization of the contact combustion gas sensor The sensor output at the time of air base can be easily acquired. This eliminates the need for an adsorbent and a calibration gas container for acquiring the air base as in the past, so that the detection accuracy of the gas concentration measuring device can be improved and the configuration can be simplified to reduce costs. Can contribute. In addition, since the sensor output at the time of air base can be acquired immediately before measuring the concentration, it can easily cope with air base fluctuations due to changes over time, environmental changes, etc. There is no need to make corrections. In particular, it is effective for adsorptive gases such as volatile organic compounds (VOC), and the output at the air base and the target when the adsorption period is shortened so that the test gas molecules are hardly adsorbed on the sensor surface. The gas concentration can be measured more accurately by comparing the output when the adsorption period is long enough for the detection gas molecules to sufficiently adsorb.

  According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, the concentration of the test gas is measured based on the continuous combustion sensor output and the air base sensor output. Therefore, since the concentration of the test gas can be measured based on the air-base sensor output corresponding to the measurement, the measurement accuracy can be improved.

  Hereinafter, an embodiment of a gas concentration measuring apparatus according to the present invention will be described with reference to the drawings of FIGS.

  As shown in FIG. 2, the gas concentration measuring apparatus 1 includes a microprocessor (MPU) 10, a drive power supply 20, an output unit 30, and a gas sensor unit 40. A driving power source 20, an output unit 30, and a gas sensor unit 40 are connected to the MPU 10.

  The MPU 10 stores a central processing unit (CPU) 11 that performs various processes and controls according to a predetermined program, a ROM 12 that is a read-only memory that stores programs for the CPU 11, various data, and the CPU 11. The RAM 13 is a readable / writable memory having an area necessary for the above processing operations.

  The CPU 11 performs drive control of the gas sensor unit 40 by executing a drive control program or the like stored in the ROM 12. That is, the CPU 11 functions as various means such as the combustion control means, the air base control means, and the concentration calculation means in the claims by executing the drive control program.

  The drive power supply 20 uses an existing commercial power supply, a battery, and the like, generates electric power necessary for the operation of each unit such as the MPU 10 and the gas sensor unit 40 of the gas concentration measurement device 1 and operates each unit of the gas concentration measurement device 1. .

  The output unit 30 outputs various data such as a gas concentration and a gas type in response to an instruction from the MPU 10. The output unit 30 uses, for example, an LCD (liquid crystal display) when displaying a gas concentration or the like, and an LED and a drive circuit when displaying the type of gas by color, blinking, or the like. Further, when outputting the gas detection result as an audible signal, a buzzer, a speaker and an output circuit are used.

  The gas sensor unit 40 includes a contact combustion type gas sensor 41 that outputs a sensor output that is sensitive to the adsorbed test gas, a drive unit 42 that drives the contact combustion type gas sensor 41, and a sensor output unit 43. .

  The catalytic combustion gas sensor 41 is intermittently driven by a drive signal supplied from the CPU 11. As shown in FIGS. 2 and 3, the catalytic combustion type gas sensor 41 includes a sensitive element part Rs and a compensating element part Rr.

The sensitive element portion Rs includes a platinum (Pt) heater 412 and a Pd / Al ₂ O ₃ catalyst layer 413 made of alumina (Al ₂ O ₃ ) carrying a platinum group, for example, palladium (Pd). , A platinum (Pt) heater 414 and an alumina (Al ₂ O ₃ ) layer 415. Specifically, as shown in FIG. 3A, the catalytic combustion type gas sensor 41 includes a silicon oxide (SiO ₂ ) film, a silicon nitride (SiN) film, and a hafnium oxide (HfO) on a silicon (Si) wafer 411. ₂ ) An insulating thin film 418 made of a film or the like is formed, on which a platinum (Pt) heater 412 and a Pd / Al ₂ O ₃ catalyst layer 413 as the sensitive element portion Rs and a platinum (Pt) heater as the compensating element portion Rr 414 and an alumina (Al ₂ O ₃ ) layer 415 are formed. Further, as shown in FIG. 3B, the concave portions 416 and 417 are formed by anisotropic etching, and the thin film diaphragms Ds and Dr are formed to reduce the heat capacity.

  Thus, both the sensitive element Rs and the compensating element Rr constitute a catalyst layer on the platinum heaters 412 and 414, the test gas is adsorbed on the catalyst on the sensitive element Rs side, and on the compensating element part Rr side. It has a structure that does not adsorb. When the heater temperature rises, the gas adsorbed on the sensitive element portion Rs side burns, and the heater temperature becomes higher than that on the compensating element portion Rr side. Since the resistance value of the platinum heaters 412 and 414 increases constantly with respect to the temperature, the temperature difference due to the combustion can be detected as a difference in resistance value of the platinum heaters 412 and 414.

  The drive unit 42 includes fixed resistors R1 and R2 that form a bridge circuit together with platinum (Pt) heaters 412 and 414, and a transistor Q1. In the bridge circuit, the collector of the transistor Q1 is connected to the connection point of the platinum (Pt) heater 412 and the resistor R2, its base is connected to the CPU 11 of the MPU 10 via the fixed resistor Rb, and its emitter is grounded. . A driving power source 20 is connected to a connection point between the platinum (Pt) heater 414 and the resistor R1.

  In the drive unit 42 configured as described above, the drive pulse generated by the MPU 10 is input to the base of the transistor Q1 through the fixed resistor Rb. The transistor Q1 is turned off when 0V is inputted to the base, and turned on when the input is about 0.6V or more, for example. Therefore, the power supply voltage is applied to the bridge circuit in conjunction with the drive pulse.

  The sensor output unit 43 includes an amplifier 431 and an A / D converter 432. The amplifier 431 amplifies the difference between the intermediate voltages V− and V + in the bridge circuit. The output of the amplifier 431 is connected to the input of the A / D converter 432. The output of the A / D converter 432 is connected to the MPU 10, and the result of A / D conversion is output to the MPU 10.

  In addition, there is a slight variation in each resistor constituting the bridge circuit, and Rr: Rs = R1: R2 may not be established in 0 gas (in the absence of gas). When equilibrium is reached, a potential difference occurs between the intermediate voltages V− and V +. This potential difference can also be reduced to 0 by finely adjusting the fixed resistors R1 and R2, but it is difficult to adjust minute variations. Therefore, an offset voltage is input to the amplifier 431 from the variable resistor R3. The configuration is possible.

  In the gas sensor unit 40 configured as described above, the voltage Vb is applied to the bridge circuit, and the intermediate voltages V− and V + for 0 gas are both Vb / 2. Here, when gas is adsorbed to the sensitive element portion Rs, when the sensor temperature rises due to the drive pulse, the adsorbed gas burns, the heater temperature on the sensitive element portion Rs side becomes higher, and the intermediate potential V + is Vb / 2. Become bigger. On the other hand, the intermediate potential V− of the fixed resistors R1 and R2 is always Vb / 2. Therefore, a potential difference is generated between the intermediate potentials V + and V−, and if the combustion by the adsorbed gas is large, the potential difference becomes large.

  As described above, the amount of gas adsorbed to the sensitive element portion Rs changes with the change in gas concentration, so that a change depending on the gas concentration can be obtained in the potential difference between the intermediate potentials V + and V−. The change is amplified by the amplifier 431 as necessary and A / D converted, and the result is output to the MPU 10 as a sensor output.

  Next, an example of the gas concentration measurement process executed by the CPU 11 described above will be described below with reference to the flowchart of FIG. The gas concentration measurement processing program is stored in the ROM 12 in advance.

  In step S1, in order to remove the gas adsorbed to the sensitive element portion Rs, the sensitive element portion Rs and the compensating element portion Rr are energized by switching the transistor Q1 to the ON state for a predetermined time, and then the process proceeds to step S2. . As a result, the gas adsorbed to the sensitive element portion Rs by power feeding is burned. The predetermined time is arbitrarily set to a time sufficient to remove the gas adsorbed on the sensitive element portion Rs.

  In step S2, by switching the transistor Q1 to the OFF state over the gas adsorption time b (for example, 3 seconds), gas is supplied to the sensitive element portion Rs in a state where energization of the sensitive element portion Rs and the compensating element portion Rr is stopped. Then, the process proceeds to step S3. As a result, gas is adsorbed to the sensitive element portion Rs. The gas adsorption time b is a time sufficient for the adsorption to proceed until the amount of gas molecules reaches a detectable amount on the sensor surface. Usually, it is about 1 to 60 seconds, and varies depending on the type of gas to be detected and the concentration.

  In step S3, by switching the transistor Q1 to the ON state over the combustion time B (for example, 0.4 seconds), the sensitive element portion Rs and the compensating element portion Rr are energized, and then the process proceeds to step S4. As a result, the gas adsorbed to the sensitive element portion Rs by power feeding is burned.

  In step S4, the sensor output output from the A / D converter 432 at a predetermined sampling rate during energization for the combustion time B is taken in as a combustion sensor output (Vg) and stored in the RAM 13 in time series, and then in step S5. Proceed to

  In step S5, by switching the transistor Q1 to the OFF state over the heat radiation time a (for example, 0.1 second), the energization of the sensitive element portion Rs and the compensating element portion Rr is stopped, and then the process proceeds to step S6. As a result, the sensitive element portion Rs and the compensation element portion Rr are returned from the heating temperature to the ambient temperature. However, since the heat radiation time a is set to be shorter than the gas adsorption time b, the gas is hardly adsorbed to the sensitive element portion Rs.

  The heat radiation time a is a time sufficient for the sensitive element Rs heated to the combustion temperature to radiate and return to room temperature in order to burn the gas adsorbed on the surface of the sensitive element Rs. The time has hardly progressed. Usually, it is 0.01 to 0.5 seconds, and varies depending on the gas species to be detected.

  In step S6, the sensitive element part Rs and the compensating element part Rr are energized by switching the transistor Q1 to the ON state over the air base time A (for example, 0.4 seconds), and then the process proceeds to step S7. As a result, the sensitive element portion Rs in a state where almost no gas is adsorbed by power feeding is burned.

  In step S7, the sensor output output from the A / D converter 432 at a predetermined sampling rate during energization of the air base time A is taken in as the air base time sensor output (Va) and stored in the RAM 13 in time series. Proceed to step S8.

  In step S8, the air base sensor output (Va) is subtracted from the combustion sensor output (Vg) of the RAM 13 (Vg-Va), and the subtraction result (waveform area) and the correspondence map of the gas concentration stored in the ROM 12 in advance. Alternatively, the gas concentration is calculated based on the conversion formula and stored in the RAM 13 as necessary. The gas concentration information indicating the gas concentration is output to the output unit 30, and then the process returns to step S2 to repeat a series of processes. . The output unit 30 outputs the input gas concentration information.

  Thus, in this best mode, in the gas concentration measurement process, steps S2 to S3 are the combustion control means in the claims, steps S5 to S6 are the air base control means, and step S8 is the concentration calculation means. Respectively.

  Next, an example of the operation (action) of the gas concentration measuring apparatus 1 according to the present invention having the above-described configuration will be described below with reference to the energization pattern shown in FIG.

  First, in FIG. 5, in order to remove the gas adsorbed to the sensitive element portion Rs, the energization to the sensitive element portion Rs and the compensating element portion Rr is applied over the combustion time B0 with the applied voltage E that becomes the combustion temperature of the sensitive element portion Rs. Done.

  When the gas adsorbed on the sensitive element portion Rs is combusted, the energization to the sensitive element portion Rs and the compensating element portion Rr is stopped over the gas adsorption time b1. When gas is adsorbed to the sensitive element portion Rs within the gas adsorption time b1, the sensitive element portion Rs and the compensating element portion Rr are energized over the combustion time B1 and adsorbed to the sensitive element portion Rs. The gas is burned. Then, the combustion sensor output (Vg) output by the contact combustion gas sensor 41 in accordance with this combustion is acquired (combustion control step Ps).

  When the energization of the sensitive element part Rs and the compensating element part Rr is stopped over the heat radiation time a1, the temperature is returned from the heating temperature of the sensitive element part Rs and the compensating element part Rr to the ambient temperature. Then, the sensitive element portion Rs and the compensating element portion Rr are energized over the air base time A1, and the sensitive element portion Rs in a state where no gas is adsorbed is burned. Then, the air base time sensor output (Va) output by the contact combustion type gas sensor 41 according to this combustion is acquired (air base time control process Pa).

  The air base sensor output (Va) is subtracted from the combustion sensor output (Vg) (Vg−Va). Based on the subtraction result (waveform area) and the gas concentration correspondence map or conversion formula stored in the ROM 12 in advance. The gas concentration is calculated, and the gas concentration is output from the output unit 30 (gas concentration measurement step).

  The combustion time control process Ps and the air base time control process Pa constitute a concentration measurement control process P. The concentration measurement control process P is repeated during the measurement period of the gas concentration measuring apparatus 1.

  Therefore, the gas concentration measuring apparatus 1 has a concentration measurement control process P and a gas concentration measurement process. That is, it has the combustion time control process Ps, the air base time control process Pa, and the gas concentration measurement process.

  Moreover, in the gas concentration measuring apparatus 1 having the above-described configuration, when the response intensity that is the sensor output difference (Vg−Va) with respect to the toluene concentration when the gas adsorption time b1 is changed, the result shown in FIG. 6 is obtained. It was.

  When the adsorption time b1 is shortened, the response intensity is decreased, and when the adsorption time b1 is increased, the response intensity (Vg−Va) is increased, but is saturated at a constant value. In other words, if the adsorption time b1 at which the response intensity (Vg−Va) is saturated is the saturated adsorption time, the accuracy is improved by comparing the response over the saturated adsorption time with the response with the shortest adsorption time b1 as much as possible. Can do.

  As described above, according to the gas concentration measuring apparatus 1 of the present invention, the energization is stopped and the test gas is adsorbed, and then energized so as to heat up to the combustion temperature. Vg is output, and energization is performed in a state where the test gas is not adsorbed after the energization is stopped so as to decrease from the combustion temperature to the ambient temperature, and the contact combustion type gas sensor 41 outputs the air-base sensor output Va, Since the gas to be detected is detected based on the sensor output Vg at the time of combustion and the sensor output Va at the time of air base, the sensor output Va at the time of air base can be easily obtained simply by controlling the energization of the catalytic combustion type gas sensor 41. can do.

  This eliminates the need for an adsorbent and a calibration gas container for acquiring the air base as in the past, so that the detection accuracy of the gas concentration measuring device can be improved and the configuration can be simplified to reduce costs. Can contribute. In addition, since the sensor output at the time of air base can be acquired immediately before measuring the concentration, it can easily cope with air base fluctuations due to changes over time, environmental changes, etc. There is no need to make corrections.

  Further, since the concentration of the test gas is measured based on the continuous combustion sensor output Vg and the air base sensor output Va, the test gas is based on the air base sensor output Va corresponding to the measurement time. Therefore, the measurement accuracy can be improved.

  In the best mode described above, the gas sensor unit 40 shown in FIG. 2 can be configured as shown in FIG. Note that the same or corresponding parts as those described in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 7, the drive pulse wave generated by the MPU 10 is converted to an analog voltage by a D / A converter (not shown) and input to the + input terminal of the error amplifier 431 via the fixed resistor R6. The voltage Vb of the bridge circuit is divided by the fixed resistor R5 and the fixed resistor R7 and input to the negative input terminal of the error amplifier 431. The error amplifier 431 operates so that the difference generated between these two inputs becomes zero.

  For example, when the voltage at the − input terminal is lower than that at the + input terminal, the output voltage of the error amplifier 431 rises and is input to the base of the transistor Q1 via the fixed resistor R4. As a result, the current flowing between the collector and emitter of the transistor Q1 increases, and the voltage Vb of the bridge circuit increases. As a result, the voltage at the negative input terminal of the error amplifier 431 increases and is controlled by the voltage output from the D / A. Conversely, when the voltage at the − input terminal is higher than the voltage at the + input terminal, the output voltage of the error amplifier 431 decreases, so that the current flowing between the collector and the emitter of the transistor Q1 decreases, and the voltage of the bridge circuit. Vb decreases. As a result, the voltage input to the negative input terminal of the error amplifier 431 decreases and is controlled by the voltage output from the D / A. In this way, the voltage Vb of the bridge circuit can be freely set by the voltage output from the D / A converter.

  In the configuration of the gas sensor unit 40 shown in FIG. 2 described above, the sensor temperature of the sensitive element unit Rs when the energization is turned off decreases to room temperature. However, when the room temperature changes, the time required for the sensor temperature to drop changes, resulting in an error in the amount of gas adsorbed to the sensitive element portion Rs. Therefore, by controlling the voltage Vb of the bridge circuit shown in FIG. 7, for example, the sensor temperature when the energization is turned off can be set to a temperature higher than the room temperature range to be used without setting the room temperature. Moreover, it can also be made variable according to the room temperature separately detected by the temperature sensor etc.

  In the above-described best mode, the case where the gas concentration measuring device 1 executes the air base time control process Pa after the combustion time control process Ps has been described. It can also be set as embodiment which performs control process Ps.

It is a lineblock diagram showing the basic composition of the gas concentration measuring device concerning the present invention. It is a block diagram which shows schematic structure of the gas concentration measuring apparatus which concerns on this invention. The structural example of the contact combustion type gas sensor in FIG. 2 is shown, (A) is a top view, (B) is sectional drawing of the arrow direction which passes along XX in (A). It is a flowchart which shows an example of the gas concentration measurement process which concerns on this invention which CPU in FIG. 2 performs. It is a figure for demonstrating the example of electricity supply of the gas concentration measuring apparatus which concerns on this invention. It is a graph which shows the relationship between a sensor output difference and adsorption | suction time. It is a block diagram which shows the other Example of the gas sensor part in FIG.

Explanation of symbols

1 Gas concentration measuring device 11a Concentration calculating means (CPU)
11b Combustion control means (CPU)
11c Air base control means (CPU)
40 Gas Sensor Unit 41 Contact Combustion Gas Sensor

Claims (3)

Gas concentration measurement comprising: a contact combustion type gas sensor that outputs a sensor output in response to the adsorbed sample gas; and a concentration calculation means that measures the concentration of the sample gas based on the sensor output of the contact combustion type gas sensor In the device
After the energization of the catalytic combustion type gas sensor is stopped so that the test gas is adsorbed to the catalytic combustion type gas sensor, the catalytic combustion type gas sensor is energized so as to have a combustion temperature at which the adsorbed test gas is combusted. Combustion control means for performing control,
Air-base control means for controlling energization of the catalytic combustion gas sensor in a state where the test gas is not adsorbed after the energization of the catalytic combustion gas sensor is stopped so as to decrease from the combustion temperature to the ambient temperature. And having
The concentration calculation means includes a combustion sensor output of the catalytic combustion gas sensor in response to energization by the combustion control means and an air base sensor output of the contact combustion gas sensor in response to energization by the air base control means. A gas concentration measuring device characterized in that the concentration of the test gas is calculated based on the above.   The gas concentration measuring apparatus, wherein the concentration calculating means calculates the concentration of the test gas based on the continuous combustion sensor output and the air base sensor output. A gas concentration measuring method for measuring the concentration of the test gas using a catalytic combustion type gas sensor that outputs a sensor output sensitive to the adsorbed test gas,
After the energization of the catalytic combustion type gas sensor is stopped so that the test gas is adsorbed to the catalytic combustion type gas sensor, the energization of the catalytic combustion type gas sensor is performed so as to reach a combustion temperature at which the adsorbed test gas is combusted. A combustion process to be performed;
After the energization of the catalytic combustion gas sensor is stopped so that the catalytic combustion gas sensor decreases from the combustion temperature to the ambient temperature, the air that energizes the catalytic combustion gas sensor in a state where the test gas is not adsorbed. A base process;
Based on the sensor output during combustion of the catalytic combustion type gas sensor according to energization of the combustion process and the air base time sensor output of the contact combustion type gas sensor according to energization of the air base process. A gas concentration measuring step for measuring the concentration;
A gas concentration measuring method comprising:

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