JP7415494B2 - gas sensor - Google Patents

Description

The present invention relates to a gas sensor that detects gas contained in an atmosphere, and particularly to a gas sensor that calculates an output signal indicating the concentration of a gas to be detected based on a detected voltage.

A gas sensor detects the concentration of a gas to be measured contained in an atmosphere, and among them, a type of gas sensor that heats a temperature measuring element such as a thermistor using a heater resistance is excellent in miniaturization. For example, the gas sensor described in Patent Document 1 includes an exhaust gas side electrode, a reference gas side electrode, and a heater, and improves the controllability of heater energization by changing the control duty ratio according to changes in the power supply voltage. I'm letting you do it.

Japanese Patent Application Publication No. 2003-50226

However, when the power supply voltage changes, the detection voltage output from the sensor element also changes, so if the output signal indicating the concentration of the target gas to be detected is directly calculated based on the detection voltage, errors due to fluctuations in the power supply voltage will occur. There was a problem that occurred.

Therefore, the present invention provides a type of gas sensor that calculates an output signal indicating the concentration of a gas to be detected based on a detection voltage. The purpose is to calculate.

A gas sensor according to the present invention includes a first gas sensor section that is connected to a first power source and includes a first temperature measuring element whose resistance value changes depending on the concentration of a gas to be measured, and an output from the first gas sensor section. and a signal processing circuit that calculates an output signal indicative of the concentration of the gas to be detected based on the detected voltage, the signal processing circuit correcting the output signal according to the voltage of the first power supply. .

According to the present invention, since the output signal is corrected according to the voltage of the first power supply, even when the voltage of the first power supply fluctuates, the output signal indicating the concentration of the gas to be detected is corrected. It becomes possible to calculate correctly.

In the present invention, the signal processing circuit includes a voltage dividing circuit that divides the voltage of the first power supply, and the signal processing circuit may correct the output signal according to the divided voltage output from the voltage dividing circuit. . According to this, even if the voltage of the first power supply is high, it is possible to accurately grasp the current voltage value.

In the present invention, the signal processing circuit may correct the output signal according to the difference or ratio between the divided voltage obtained during the calibration operation and the divided voltage obtained during the measurement operation. According to this, it becomes possible to perform correction according to the voltage during the measurement operation.

In the present invention, the signal processing circuit may adjust the amount of correction of the output signal according to the difference or ratio between the detected voltage and the divided voltage obtained during the calibration operation. According to this, more accurate correction becomes possible.

The gas sensor according to the present invention further includes a temperature sensor part that is connected to the first power source and includes a second temperature measuring element whose resistance value changes depending on the environmental temperature, and the first gas sensor part is connected to the first temperature measuring element. The signal processing circuit further includes a first heater resistor that heats the hot body, and the signal processing circuit controls a first control voltage to be applied to the first heater resistor according to the output voltage of the temperature sensor unit and the voltage of the first power supply. It doesn't matter if you calculate it. According to this, it becomes possible to apply an appropriate control voltage to the first heater resistor according to the power supply voltage.

In the present invention, the temperature sensor section includes a second temperature sensing element and a first resistor connected in series between the first power source and the ground potential, and the voltage dividing circuit includes the first power source and the ground potential. The output voltage from the temperature sensor section is output from the connection point between the second temperature sensing element and the second resistor, and the output voltage is output from the connection point between the second temperature sensing element and the second resistance, and the output voltage is output from the voltage dividing circuit. The divided voltage outputted from the second resistor and the third resistor may be outputted from the connection point between the second resistor and the third resistor, and the difference in the resistance values of the first to third resistors may be 1% or less. According to this, it is possible to reduce errors caused by variations in resistance values.

The gas sensor according to the present invention further includes a second gas sensor section including a third temperature measuring element and a second heater resistor that heats the third temperature measuring element, The body is connected in series between the first power source and the ground potential, the detection voltage is output from the connection point between the first temperature measuring body and the third temperature measuring body, and the signal processing circuit is connected to the temperature sensor section. A second control voltage to be applied to the second heater resistor is calculated according to the output voltage of the output voltage and the voltage of the first power supply. Therefore, the first temperature measuring body and the third temperature measuring body may be heated to different temperatures. According to this, it becomes possible to obtain a detection signal according to the concentration of the gas to be measured from the connection point between the first temperature measuring body and the third temperature measuring body.

In the present invention, the signal processing circuit is operated by a second power source different from the first power source, and the voltage of the first power source may be higher than the voltage of the second power source. According to this, high detection sensitivity can be obtained and power consumption can be reduced.

As described above, according to the gas sensor according to the present invention, even when the power supply voltage fluctuates, it is possible to correctly calculate the output signal indicating the concentration of the gas to be detected.

FIG. 1 is a circuit diagram showing the configuration of a gas sensor 10 according to an embodiment of the present invention. FIG. 2 is a top view for explaining the configuration of the sensor section S. As shown in FIG. FIG. 3 is a cross-sectional view taken along line AA shown in FIG. FIG. 4 is a flowchart for explaining the operation of the gas sensor 10. FIG. 5 is a graph showing the relationship between environmental temperature and control voltages Vmh1 and Vmh2. FIG. 6 is a graph showing the relationship between fluctuations in power supply potential Vcc1 and CO ₂ gas detection error.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing the configuration of a gas sensor 10 according to an embodiment of the present invention.

As shown in FIG. 1, the gas sensor 10 according to this embodiment includes a sensor section S and a signal processing circuit 20. Although not particularly limited, the gas sensor 10 according to this embodiment detects the concentration of CO ₂ gas in the atmosphere.

The sensor section S is a thermal conduction gas sensor for detecting the concentration of CO ₂ gas, which is a detection target gas, and includes a first gas sensor section S1, a second gas sensor section S2, and a temperature sensor section S3. There is. The first gas sensor section S1 includes a thermistor Rd1, which is a first temperature measuring element, and a heater resistor MH1, which heats the thermistor Rd1. Similarly, the second gas sensor section S2 includes a thermistor Rd2, which is a third temperature measuring element, and a heater resistor MH2 that heats the thermistor Rd2. On the other hand, the temperature sensor section S3 includes a thermistor Rd3 which is a second temperature measuring element.

As shown in FIG. 1, thermistors Rd1 and Rd2 are connected in series between a wiring to which power supply potential Vcc1 is supplied and a wiring to which ground potential GND is supplied. On the other hand, the thermistor Rd3 and the resistor R1 are connected in series between the wiring to which the power supply potential Vcc1 is supplied and the wiring to which the ground potential GND is supplied. Thermistors Rd1 to Rd3 are made of a material having a negative temperature coefficient of resistance, such as composite metal oxide, amorphous silicon, polysilicon, germanium, or the like. Of these, the thermistors Rd1 and Rd2 both detect the concentration of CO ₂ gas, but their operating temperatures are different from each other, as will be described later.

Thermistor Rd1 is heated by heater resistor MH1. The heating temperature of the thermistor Rd1 by the heater resistor MH1 is, for example, 150°C. If CO ₂ gas exists in the measurement atmosphere while the thermistor Rd1 is heated, the heat dissipation characteristics of the thermistor Rd1 change depending on its concentration. Such a change appears as a change in the resistance value of the thermistor Rd1. When the heating temperature of the thermistor Rd1 is 150° C., the resistance value of the thermistor Rd1 changes with the first sensitivity depending on the concentration of CO ₂ gas. The first sensitivity has a sensitivity that can sufficiently change the detection voltage _VCO2 appearing at the connection point between the thermistor Rd1 and thermistor Rd2. Further, if water vapor exists in the measurement atmosphere, the heat dissipation characteristics of the thermistor Rd1 change depending on its concentration.

Thermistor Rd2 is heated by heater resistor MH2. The heating temperature of the thermistor Rd2 by the heater resistor MH2 is, for example, 300°C. Even if CO ₂ gas exists in the measurement atmosphere while the thermistor Rd2 is heated, the resistance value of the thermistor Rd2 hardly changes. This means that when the heating temperature of thermistor Rd2 is 300°C, the resistance value of thermistor Rd2 changes at the second sensitivity depending on the concentration of CO ₂ gas, but the second sensitivity is higher than the first sensitivity. This is because the sensitivity is significantly low, preferably 1/10 or less of the first sensitivity, and more preferably approximately zero. Therefore, even if the concentration of CO ₂ gas changes, the resistance value of the thermistor Rd2 hardly changes. On the other hand, if water vapor exists in the measurement atmosphere, the heat dissipation characteristics of the thermistor Rd2 change depending on its concentration.

As described above, the thermistor Rd1 and thermistor Rd2 are connected in series, and the detection voltage _VCO2 is output from the connection point. On the other hand, the output voltage Va of the temperature sensor section S3 is output from the connection point between the thermistor Rd3 and the resistor R1. The detection voltage V _CO2 and the output voltage Va are input to the signal processing circuit 20.

The signal processing circuit 20 includes a voltage dividing circuit 21, a buffer 22, a differential amplifier 23, an AD converter (ADC) 24, a DA converter (DAC) 25, and a control section 26. The voltage dividing circuit 21 consists of resistors R2 and R3 connected in series between the wiring to which the power supply potential Vcc1 is supplied and the wiring to which the ground potential GND is supplied, and divides the voltage from the connection point between the resistors R2 and R3. A voltage 1/2Vcc_in is output. Other circuits constituting the signal processing circuit 20 are supplied with a power supply potential Vcc2 different from the power supply potential Vcc1, and operate with a voltage between the power supply potential Vcc2 and the ground potential GND. Although not particularly limited, the power supply potential Vcc1 is higher than the power supply potential Vcc2. As an example, the power supply potential Vcc1 is 3V, and the power supply potential Vcc2 is 1.8V. In this way, when Vcc1>Vcc2, the detection sensitivity of the sensor section S is increased and the power consumption of the signal processing circuit 20 can be suppressed. When the power supply potential Vcc1 is high, voltage fluctuations are likely to occur, but as described later, in this embodiment, measurement errors caused by voltage fluctuations in the power supply potential Vcc1 are canceled.

Buffer 22 generates temperature signal Vtemp by buffering output voltage Va. Further, the differential amplifier 23 compares the detection voltage _VCO2 and the reference voltage Vref, and amplifies the difference. The temperature signal Vtemp output from the buffer 22 and the gas detection signal Vamp output from the differential amplifier 23 are input to the AD converter 24.

The AD converter 24 digitally converts the value of the divided voltage 1/2 Vcc_in, the temperature signal Vtemp, and the gas detection signal Vamp, and supplies the values to the control unit 26. On the other hand, the DA converter 25 generates a reference voltage Vref and control voltages Vmh1 and Vmh2 by converting the reference signal supplied from the control unit 26 into analog. The control unit 26 calculates an output signal Vout indicating the current concentration of CO ₂ gas based on the digitally converted gas detection signal Vamp. Although details will be described later, in calculating the output signal Vout, correction is performed according to the current divided voltage 1/2Vcc_in. Furthermore, the levels of the control voltages Vmh1 and Vmh2 are calculated using the temperature signal Vtemp.

FIG. 2 is a top view for explaining the configuration of the sensor section S. As shown in FIG. Further, FIG. 3 is a cross-sectional view taken along the line AA shown in FIG. 2. Note that the drawings are schematic, and for convenience of explanation, the relationship between thickness and planar dimensions, the thickness ratio between devices, etc. may differ from the actual structure within the range where the effects of this embodiment can be obtained. It doesn't matter if you stay there.

The sensor section S is a thermal conduction type gas sensor that detects gas concentration based on changes in heat dissipation characteristics depending on the concentration of CO ₂ gas, and as shown in FIGS. 2 and 3, two gas sensor sections S1 and S2 are used. , a temperature sensor section S3 disposed between the gas sensor section S1 and the gas sensor section S2, and a ceramic package 51 that accommodates these sensor sections S1 to S3.

The ceramic package 51 is a box-shaped case with an open top, and a lid 52 is provided at the top. The lid 52 has a plurality of vent holes 53, which allow CO ₂ gas in the atmosphere to flow into the ceramic package 51. Note that the lid 52 is omitted in FIG. 2 in consideration of the ease of viewing the drawing.

Although not particularly limited, in this embodiment, three sensor sections S1 to S3 are integrated on a single substrate 61. The substrate 61 is formed with three cavities 61a to 61c corresponding to the three sensor parts S1 to S3, respectively.

The substrate 61 includes insulating films 62 and 63, heater resistors MH1 and MH2 provided on the insulating film 63, a heater protective film 64 that covers the heater resistors MH1 and MH2, and heater protectors at positions overlapping with the cavities 61a to 61c, respectively. It includes thermistors Rd1 to Rd3 and thermistor electrodes 35, 45, 65 provided on the film 64, and a thermistor protective film 66 that covers the thermistors Rd1 to Rd3 and thermistor electrodes 35, 45, 65.

The substrate 61 is not particularly limited as long as it has appropriate mechanical strength and is suitable for microfabrication such as etching, and may be a silicon single crystal substrate, a sapphire single crystal substrate, a ceramic substrate, or a quartz substrate. , a glass substrate, etc. can be used. The insulating films 62 and 63 are made of an insulating material such as silicon oxide or silicon nitride. The heater resistors MH1 and MH2 are made of a metal material having a relatively high melting point, such as molybdenum (Mo), platinum (Pt), gold (Au), tungsten (W), tantalum (Ta), palladium (Pd), Iridium (Ir) or an alloy containing two or more of these is suitable. Thermistors Rd1 to Rd3 are made of a material with a negative temperature coefficient of resistance, such as composite metal oxide, amorphous silicon, polysilicon, germanium, or the like. Here, a thermistor is used as the temperature measuring element because it has a higher temperature coefficient of resistance than a platinum temperature measuring element or the like, and therefore can provide greater detection sensitivity. As the material of the heater protection film 64, the same material as the insulating film 63 can be used.

The thermistor electrodes 35, 45, 65 are a pair of electrodes with a predetermined interval, the thermistor Rd1 is provided between the pair of thermistor electrodes 35, the thermistor Rd2 is provided between the pair of thermistor electrodes 45, and the thermistor Rd2 is provided between the pair of thermistor electrodes 45, A thermistor Rd3 is provided between the electrodes 65. As a result, the resistance values between the pair of thermistor electrodes 35, 45, and 65 are determined by the resistance values of the thermistors Rd1 to Rd3, respectively. The materials for the thermistor electrodes 35, 45, and 65 include molybdenum (Mo), platinum (Pt), gold (Au), tungsten (W), tantalum (Ta), palladium (Pd), iridium (Ir), or any of these. An alloy containing two or more types is suitable.

As shown in FIG. 2, both ends of heater resistor MH1 are connected to electrode pads 37a, 37b, respectively, and both ends of heater resistor MH2 are connected to electrode pads 47a, 47b, respectively. Further, both ends of the thermistor electrode 35 are connected to electrode pads 37c and 37d, respectively, both ends of the thermistor electrode 45 are connected to electrode pads 47c and 47d, respectively, and both ends of the thermistor electrode 65 are connected to electrode pads 67a and 67b, respectively. . These electrode pads are connected to package electrodes 54 provided on the ceramic package 51 via bonding wires 55. The package electrode 54 is connected to the signal processing circuit 20 shown in FIG. 1 via an external terminal 56 provided on the back surface of the ceramic package 51.

The above is the configuration of the gas sensor 10 according to this embodiment. Next, the operation of the gas sensor 10 according to this embodiment will be explained.

The gas sensor 10 according to the present embodiment takes advantage of the fact that the thermal conductivity of CO ₂ gas is significantly different from that of air, and detects changes in the heat dissipation characteristics of the thermistors Rd1 and Rd2 due to the concentration of CO ₂ gas using the gas detection voltage. Take out as V _CO2 . However, since the thermal conductivity of the measurement atmosphere changes not only depending on the concentration of CO ₂ gas but also on the humidity, that is, the concentration of water vapor, the influence of humidity causes measurement errors. Therefore, in the gas sensor 10 according to the present embodiment, the thermistor Rd1 is heated to, for example, 150° C. using the heater resistor MH1, and the thermistor Rd2 is heated to, for example, 300° C. using the heater resistor MH2. When the heating temperature is 150°C, the heat dissipation characteristics of thermistor Rd1 change greatly depending on the concentration of CO ₂ gas, whereas when the heating temperature is 300°C, the heat dissipation characteristics of thermistor Rd2 change depending on the concentration of CO ₂ gas. The heat dissipation characteristics hardly change. On the other hand, whether the heating temperature is 150°C or 300°C, the heat dissipation characteristics of thermistors Rd1 and Rd2 change depending on the humidity, so by connecting thermistors Rd1 and Rd2 in series, the influence of humidity can be canceled. can do. Here, if there is a difference in sensitivity between the thermistors Rd1 and Rd2 with respect to humidity, it is possible to reduce the sensitivity difference by connecting a correction resistor in parallel to the thermistor Rd1 or thermistor Rd2.

In addition, the gas sensor 10 according to the present embodiment has a control voltage Vmh1 based on the temperature signal Vtemp and the current partial voltage 1/2Vcc_in so that the heating temperatures of the thermistors Rd1 and Rd2 remain constant even if the environmental temperature changes. , Vmh2 are adjusted. Furthermore, in the gas sensor 10 according to the present embodiment, correction is performed in accordance with the current divided voltage 1/2 Vcc_in so that the influence of fluctuations in the power supply potential Vcc1 is canceled even when calculating the output signal Vout.

FIG. 4 is a flowchart for explaining the operation of the gas sensor 10 according to this embodiment.

In the operation of the gas sensor 10, a calibration operation is first performed (step S10). The calibration operation is an operation in which the partial voltage 1/2 Vcc_in and the gas detection signal Vamp are read and predetermined calculations are performed in a state where the environmental temperature, humidity, and concentration of the gas to be measured are stable. The calibration operation may be performed not only when the gas sensor 10 is started, but also at regular intervals after the gas sensor 10 is started. In the calibration operation, first, the divided voltage 1/2 Vcc_in and the gas detection signal Vamp are digitally converted by the AD converter 24, the initial level of the divided voltage 1/2 Vcc_in is stored (step S11), and the control unit 26 converts the divided voltage 1/2 Vcc_in to digital. A voltage ratio A is calculated (step S12). The voltage ratio A is determined by calculating the ratio (1/2Vcc_in÷ _VCO2 ) of the divided voltage 1/2Vcc_in and the detected voltage _VCO2 . Instead of calculating the voltage ratio A, the difference between the divided voltage 1/2 Vcc_in and the detected voltage V _CO2 may be calculated. The detected voltage V _CO2 can be calculated by the control unit 26 performing the calculation of equation (1).
V _CO2 = (Vamp-Vref)/AMP+Vref...(1)
Here, “AMP” is the amplification ratio of the differential amplifier 23. The calculated voltage ratio A is stored inside the control unit 26 (step S13).

After completing a series of calibration operations (step S10), a measurement operation for actually measuring the concentration of the gas to be measured is performed (step S20). The measurement operation may be performed intermittently at predetermined intervals. In the measurement operation, first, the divided voltage 1/2 Vcc_in is read (step S21). Ideally, the level of the divided voltage 1/2Vcc_in is the same as the initial level obtained during the calibration operation, but if there is a fluctuation in the power supply potential Vcc1, a potential difference will occur between the two, so this potential difference Vdif is calculated (step S22). Instead of the potential difference Vdif, the ratio between the divided voltage 1/2 Vcc_in saved in step S11 and the divided voltage 1/2 Vcc_in read in step S21 may be used. Next, the current level of the power supply potential Vcc1 is calculated by doubling the value of the read divided voltage 1/2 Vcc_in (step S23).

Next, the temperature signal Vtemp is read (step S24), and a temperature value Ta is calculated based on the level of the power supply potential Vcc1 calculated in step S23 and the level of the temperature signal Vtemp read in step S24 (step S25). The temperature value Ta is calculated by calculating the current resistance value Rref of the thermistor Rd3 by calculating the equation (2), and then calculating the temperature value Ta by calculating the equation (3).

In equations (2) and (3), "R" is the resistance value of resistor R1, "B" is the temperature coefficient of thermistor Rd3, and Rref@25 is the resistance value of thermistor Rd3 when the environmental temperature is 25°C. Both use digital values stored in the control unit 26 in advance. Further, "1/2Vcc_in" is a digital value of the divided voltage 1/2Vcc_in, and "Va" is a digital value of the temperature signal Vtemp.

Next, the reference voltage Vref and control voltages Vmh1 and Vmh2 are calculated using the temperature value Ta calculated in step S25 (step S26). Control voltages Vmh1 and Vmh2 can be calculated by calculating equations (4) and (5), respectively.
Vmh1=-0.00301×Ta+1.15 (4)
Vmh2=-0.00151×Ta+2.19 (5)
As a result, the reference voltage Vref corresponding to the current environmental temperature is applied to the differential amplifier 23, and the thermistors Rd1 and Rd2 are heated to predetermined temperatures (for example, 150° C. and 300° C.), respectively. FIG. 5 is a graph showing the relationship between environmental temperature and control voltages Vmh1 and Vmh2. As shown in FIG. 5, it can be seen that the control voltages Vmh1 and Vmh2 decrease linearly as the environmental temperature increases.

Next, the gas detection signal Vamp is read (step S27), and after correcting the gas detection signal Vamp using the potential difference Vdif (step S28), the output signal Vout is calculated (step S29). The gas detection signal Vamp is corrected by the control unit 26 calculating equation (4).
Vamp (after correction) = Vamp + Vdif x AMP/A (4)
This cancels the offset of the gas detection signal Vamp caused by fluctuations in the power supply potential Vcc1, making it possible to generate the correct output signal Vout.

FIG. 5 is a graph showing the relationship between fluctuations in the power supply potential Vcc1 and CO ₂ gas detection error, where the solid line indicates the detection error in the gas sensor 10 according to the present embodiment, and the broken line indicates the current partial voltage 1/2 Vcc_in. It shows the detection error without the correction used.

As shown in FIG. 5, when correction using the current divided voltage 1/2 Vcc_in is not performed, a large detection error occurs due to a slight variation in the power supply potential Vcc1, whereas the gas sensor 10 according to the present embodiment According to the graph, it can be seen that almost no detection error occurs even if the power supply potential Vcc1 fluctuates.

CO ₂ gas detection errors also occur due to variations in the resistance values of the resistors R1 to R3. In order to reduce detection errors caused by variations in the resistance values of the resistors R1 to R3, it is necessary to design the resistance values of the resistors R1 to R3 to be the same value, and to suppress the variation in resistance values to 1% or less. It is valid.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention. Needless to say, it is included within the scope.

For example, in the above embodiment, the case where the gas to be measured is CO ₂ gas has been described as an example, but the present invention is not limited to this. Further, it is not essential that the sensor section used in the present invention be a thermal conduction type sensor, and it may be a sensor of another type such as a catalytic combustion type.

10 Gas sensor 20 Signal processing circuit 21 Voltage dividing circuit 22 Buffer 23 Differential amplifier 24 AD converter 25 DA converter 26 Control section 35, 45, 65 Thermistor electrodes 37a to 37d, 47a to 47d, 67a, 67b Electrode pad 51 Ceramic package 52 Lid 53 Vent hole 54 Package electrode 55 Bonding wire 56 External terminal 61 Substrate 61a to 61c Cavity 62, 63 Insulating film 64 Heater protective film 65 Thermistor electrode 66 Thermistor protective film MH1, MH2 Heater resistor R1 to R3 Resistor Rd1 to Rd3 Thermistor S Sensor section S1 First gas sensor section S2 Second gas sensor section

Claims (7)

a first gas sensor section that is connected to a first power source and includes a first temperature measuring element whose resistance value changes depending on the concentration of the gas to be detected ;
a signal processing circuit that calculates an output signal indicating the concentration of the detection target gas based on the detection voltage output from the first gas sensor section,
The signal processing circuit includes a voltage dividing circuit that divides the voltage of the first power supply,
The gas sensor, wherein the signal processing circuit corrects the output signal according to a divided voltage output from the voltage dividing circuit. 2. The signal processing circuit corrects the output signal according to a difference or ratio between the divided voltage obtained during a calibration operation and the divided voltage obtained during a measurement operation. Gas sensor listed. The gas sensor according to claim 2, wherein the signal processing circuit adjusts the amount of correction of the output signal according to a difference or ratio between the detected voltage and the divided voltage obtained during a calibration operation. further comprising a temperature sensor unit connected to the first power source and including a second temperature measuring element whose resistance value changes depending on the environmental temperature,
The first gas sensor section further includes a first heater resistor that heats the first temperature sensing element,
2. The signal processing circuit calculates a first control voltage to be applied to the first heater resistor according to the output voltage of the temperature sensor section and the voltage of the first power source. 4. The gas sensor according to any one of 3 to 3. The temperature sensor section includes the second temperature measuring element and a first resistor connected in series between the first power source and ground potential,
The voltage divider circuit includes second and third resistors connected in series between the first power source and ground potential,
The output voltage output from the temperature sensor unit is output from a connection point between the second temperature measuring body and the second resistor,
The divided voltage output from the voltage dividing circuit is output from a connection point between the second resistor and the third resistor,
5. The gas sensor according to claim 4, wherein a difference in resistance values of the first to third resistors is 1% or less. further comprising a second gas sensor section including a third temperature measuring element and a second heater resistor that heats the third temperature measuring element;
The first temperature measuring body and the third temperature measuring body are connected in series between the first power source and ground potential,
The detection voltage is output from a connection point between the first temperature measuring body and the third temperature measuring body,
The signal processing circuit calculates a second control voltage to be applied to the second heater resistor according to the output voltage of the temperature sensor unit and the voltage of the first power supply,
The first control voltage and the second control voltage have different values, so that the first temperature measuring element and the third temperature measuring element are heated to different temperatures. The gas sensor according to claim 4 or 5. The signal processing circuit operates on a second power source different from the first power source,
The gas sensor according to any one of claims 1 to 6, wherein the voltage of the first power source is higher than the voltage of the second power source.

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