JP2023115685A - gas detector - Google Patents

Abstract

To provide a gas detector capable of precisely correcting sensor output of a heat-conducting gas sensor and precisely detecting gas concentration.SOLUTION: Temperature/moisture correction for correcting variations in a temperature difference between a reference temperature and a measurement environment temperature and variations in a moisture difference between reference moisture and measurement environment moisture is performed and oxygen correction corresponding to an oxygen concentration of a measurement environment atmosphere is performed to sensor output acquired by a heat-conducting gas sensor for gas to be inspected in a measurement environment atmosphere. In the temperature/moisture correction, a sensor output value acquired by a heat-conducting element is subjected to temperature correction on the basis of the temperature difference between the reference temperature and the measurement environment temperature by a correlation relational expression using a temperature correction coefficient corresponding to a detection object gas type and a base gas type. A temperature correction sensor output value obtained by the temperature correction is subjected to moisture correction by a correlation relational expression using a moisture correction coefficient corresponding to a detection object gas type and a base gas type.SELECTED DRAWING: Figure 4

Description

The present invention relates to a gas detector equipped with a heat conduction type gas sensor.

Currently, as one of the gas sensors for detecting combustible gases, for example, a thermal conductivity gas sensor is known that detects changes in the thermal conductivity of the gas to be detected as the concentration of the gas to be detected. For example, it is suitably used to detect high-concentration combustible gases exceeding 100% LEL and combustible gases with an oxygen concentration of 10% or less.
A thermal conduction type gas sensor has a thermal conduction element made of, for example, a metal coil. When the detection target gas comes into contact with the detection target gas while the heat conduction element is energized, the state of heat dissipation changes due to the thermal conductivity inherent to the detection target gas. , which changes the temperature of the heat-conducting element. As the temperature of the heat conducting element changes, the resistance value of the metal coil forming the heat conducting element changes, and the concentration of the gas to be detected is measured based on the amount of change in the resistance value.

In the thermal conductivity type gas sensor, the sensor output fluctuates (drifts) depending on the temperature and humidity of the measurement environment atmosphere. For this reason, a thermal conduction gas sensor has been proposed that is provided with a temperature detection unit and a humidity detection unit so as to compensate for fluctuations in the sensor output due to the temperature and humidity of the measurement environment atmosphere (for example, see Patent Document 1). .).

JP 2018-194409 A

However, in the thermal conductivity type gas sensor, it is difficult to sufficiently compensate for fluctuations in the sensor output only by performing temperature correction and humidity correction on the sensor output, and it is difficult to perform gas concentration detection with high accuracy. It became clear.

SUMMARY OF THE INVENTION The present invention has been completed in view of the above circumstances, and aims to accurately correct the sensor output of a heat conduction type gas sensor according to the environmental conditions of the measurement atmosphere, and to perform gas concentration detection with high accuracy. It is an object of the present invention to provide a gas detector capable of

A gas detector according to the present invention is a gas detector comprising a heat-conducting gas sensor, wherein the heat-conducting gas sensor comprises a heat-conducting element and a heat-conducting gas sensor drive control section for controlling the operation of the heat-conducting element. and the thermal conductivity type gas sensor drive control unit detects the sensor output obtained for the gas to be tested in the atmosphere of the measurement environment, the fluctuation due to the temperature difference between the reference temperature and the measurement environment temperature, and the reference humidity and the measurement environment humidity. It has a function of performing temperature and humidity correction that corrects fluctuations due to the humidity difference between and oxygen correction according to the oxygen concentration of the measurement environment atmosphere, and in the temperature and humidity correction, the sensor obtained by the heat conduction element The output value is temperature-corrected based on the temperature difference between the reference temperature and the measurement environment temperature by a correlation formula using a temperature correction coefficient corresponding to the detection target gas type and the base gas type, and the temperature correction is performed. The temperature corrected sensor output value obtained by is corrected for humidity by a correlation formula using a humidity correction coefficient according to the type of gas to be detected and the type of base gas. It is a thing.

According to the invention of claim 1, the temperature correction and humidity correction of the sensor output of the heat conduction type gas sensor are performed using the correlation formulas corresponding to the detection target gas species and the base gas species, respectively. The effect of the gas species and the effect of the base gas species are compensated. Moreover, since oxygen correction is performed according to the oxygen concentration in the measurement environment atmosphere, the floating of the zero point with respect to the base gas is corrected, so that the influence due to the oxygen concentration is compensated. Therefore, it is possible to accurately correct the sensor output of the thermal conduction gas sensor according to the environmental conditions of the measurement environment atmosphere, and to perform gas concentration detection with high accuracy.

According to the second aspect of the invention, temperature correction of the gas concentration value is performed in a state in which the degree of influence of the gas concentration value acquired based on the reference calibration curve data on the correction amount is compensated. Therefore, the accuracy of sensor output correction can be further improved.

According to the third aspect of the present invention, it is possible to avoid excessive correction of the reference calibration curve data for the influence of humidity, so that it is possible to further improve the accuracy of correcting the sensor output.

According to the invention according to claim 4, in addition to being able to compensate for fluctuations in sensor output due to differences in the base gas and improve the accuracy of gas concentration detection, when an oxygen sensor is provided, the oxygen sensor can be calibrated. It is possible to efficiently perform the calibration process of the heat conduction type gas sensor, including the process.

It is a block diagram showing an outline of composition in an example of a gas detector of the present invention. FIG. 2 is an explanatory cross-sectional view showing one configuration example of a heat conduction type gas sensor; 3A is a perspective view, and FIG. 4B is a cross-sectional view cut in a direction perpendicular to the longitudinal direction; FIG. FIG. 7 is an operation flow diagram showing an example of correction processing of sensor output;

Embodiments of the gas detector of the present invention will be described below.
FIG. 1 is a block diagram showing a schematic configuration of an example of the gas detector of the present invention. This gas detector comprises a thermal conductivity type gas sensor 10 , an oxygen sensor 40 and a main controller 50 .

The heat conduction type gas sensor 10 according to the present embodiment includes a detection unit 20 having a heat conduction element 21 and a temperature/humidity detection element 25, and a heat conduction type gas sensor drive control for controlling the operation of the heat conduction element 21 and the temperature/humidity detection element 25. and a section 30 .

FIG. 2 is an explanatory cross-sectional view showing one configuration example of a heat conduction type gas sensor. This heat conduction type gas sensor 10 has a cylindrical casing 11 . In this casing 11 , an opening on one end side (upper end side in FIG. 2 ) serves as a gas introduction port 11 a through which the gas to be tested is introduced into the casing 11 . A substantially circular substrate 15 is arranged in the casing 11 along a plane perpendicular to the axial direction of the casing 11 . A temperature/humidity detection element 25 for measuring the temperature and humidity of the gas to be tested and a plurality of studs 16 are mounted on the substrate 15 .

On the substrate 15, a disk-shaped thermal conductive element housing member 17 for housing the thermal conductive element 21 is arranged. The heat-conducting element housing member 17 is made of a resin material having insulating properties and heat resistance, such as polyphenylene sulfide (PPS) resin containing fiber such as glass fiber.
A recess 19 forming a storage chamber S in which the heat conduction element 21 is stored is formed on the surface (upper surface in FIG. 2) of the heat conducting element housing member 17, and the opening of the recess 19 forms the housing chamber S. is a vent 19a for introducing the gas to be tested. The heat conducting element 21 is electrically connected to two conductive pins extending in the thickness direction of the heat conducting element housing member 17 .
Further, in the heat-conducting element housing member 17, a ventilation path 18 for introducing a gas to be detected to the temperature/humidity detecting element 25 is formed so as to extend through the heat-conducting element housing member 17 from the front surface to the rear surface thereof.
The temperature/humidity detection element 25 is arranged in a space (thermally isolated) separated from the space (storage chamber S) in which the heat conduction element 21 is arranged, so that the heat conduction element 21 The temperature data and humidity data of the test gas can be acquired without being affected by .

A circular air-permeable sheet 12 is arranged on the surface of the heat conducting element housing member 17 so as to cover the openings of the air vents 19 a and the air passages 18 . Glass wool or the like can be used as a material for forming the air-permeable sheet 12 .
A circular sintered wire mesh 13 made of, for example, stainless steel (SUS316) is placed on the air-permeable sheet 12 with its peripheral edge fixed to the inner wall surface of the casing 11. The air-permeable sheet 12 is sandwiched between the members 17 .
A sealing material 14 formed by curing an adhesive such as an epoxy resin adhesive is provided below the substrate 15 in the casing 11 so as to block the opening on the lower side of the casing 11 .

As shown in FIGS. 3A and 3B, the heat conducting element 21 is formed by winding a resistance heating element 23 having a coating film 22 on its surface, for example, in a coil shape.
The resistance heating element 23 is made of a metal having a high temperature resistance coefficient and good corrosion resistance at high temperatures, such as platinum or an alloy thereof.
The coating film 22 is made of a metal such as gold that is inert to the gas to be detected. The thickness of the coating film 22 is, for example, 100 nm. As a method for forming the coating film 22, an appropriate thin film forming method such as sputtering can be used.
An example of the configuration of the heat-conducting element 21 is as follows. is 8 to 12 turns.

The temperature/humidity detection element 25 is, for example, an electrical resistance variable element that detects the temperature and relative humidity of the gas to be tested by measuring resistance changes caused by gas contact. The temperature/humidity detection element 25 may be of a capacitance type, and is not particularly limited as long as it can detect the temperature and relative humidity of the gas to be detected.

The heat conduction type gas sensor drive control section 30 includes a microcomputer 31 , a heat conduction element drive circuit section 32 , and a temperature/humidity detection element drive circuit section 35 .
The thermal conduction element drive circuit section 32 includes a thermal conduction element power supply 33 that supplies current to the thermal conduction element 21 and an ammeter 34 that measures the current flowing through the thermal conduction element 21 .
The temperature/humidity detection element driving circuit section 35 includes a temperature/humidity detection element power supply 36 , a humidity measurement voltmeter 37 , and a temperature measurement voltmeter 38 .
The microcomputer 31 has a function of calculating the concentration of the detection target gas by correcting the sensor output obtained by the heat conducting element 21 according to the temperature, humidity, base gas type, and oxygen concentration of the measurement environment atmosphere. In this specification, unless otherwise specified, the term "humidity" refers to absolute humidity. The absolute humidity value obtained from is used.

In addition, the microcomputer 31 stores zero calibration values in the reference environment (reference temperature T ₁ [° C.], reference humidity H ₁ [mg/L]), full scale values of various detection target gases (concentration 100 vol%), concentration 100 vol% Temperature characteristics and humidity characteristics of various detection target gases, temperature characteristics and humidity characteristics of various base gases, temperature correction coefficients according to the base gas type and detection target gas type, humidity correction according to the base gas type and detection target gas type Data related to the output correction of the heat conduction type gas sensor 10 such as coefficients, reference calibration curve data corresponding to the base gas of various detection target gases in the reference environment, temperature amount correction value and humidity amount correction value of the reference calibration curve data are recorded It is
This gas detector is configured to be able to select a detection target gas type and a base gas type. Fluctuations in sensor output due to differences in base gas species are compensated for.
The gas species to be detected can be selected from, for example, methane gas (CH ₄ ), isobutane gas (i-C ₄ H ₁₀ ), paraffin hydrocarbon gas such as propane gas, hydrogen gas, and other combustible gases. It's becoming
The base gas species can be selected from, for example, nitrogen gas (N ₂ ) and inert gas, which is an inert mixed gas of nitrogen, carbon dioxide, and oxygen.

The oxygen sensor 40 includes, for example, a galvanic battery type oxygen sensor element 41 , an oxygen sensor element drive circuit section 42 having an oxygen sensor element power source 43 and an ammeter (not shown), and an operation control of the oxygen sensor element 41 . and an oxygen sensor drive control unit 45 that performs

The main control unit 50 has a function of outputting an operation command signal to the thermal conductivity type gas sensor 10 and the oxygen sensor 40 and controlling the operation of other components of the gas detector.
Further, a function of calculating the oxygen concentration contained in the gas under test in the atmosphere of the measurement environment based on the sensor output from the oxygen sensor 40 and outputting it to the microcomputer 31 in the heat conduction gas sensor drive control unit 30 of the heat conduction gas sensor 10 is provided. have.

The gas concentration calculation function of the thermal conductivity gas sensor drive controller 30, that is, the output correction of the thermal conductivity gas sensor 10 will be described below.
First, in the gas detector described above, a warm-up process for stabilizing the zero point is performed before performing gas detection. The warm-up process is performed by applying a voltage to the heat conduction element 21 that is lower than the voltage applied to the heat conduction element 21 during measurement for a predetermined period of time.

After the warm-up process, a voltage controlled to have an appropriate magnitude is applied to the heat conduction element 21 by the heat conduction type gas sensor drive control section 30 according to the operation command signal from the main control section 50 . It is heated so that the surface temperature is maintained at a predetermined temperature state. In this state, when the test gas in the atmosphere of the measurement environment is supplied to the heat conduction type gas sensor 10 and the test gas comes into contact with the heat conduction element 21, the thermal conductivity change (resistance change) of the heat conduction element 21 is A current value is measured by an ammeter 34 and input to the microcomputer 31 of the heat conduction type gas sensor drive control unit 30 as a sensor output. In correcting the sensor output, the output ratio of the sensor output obtained by the heat conduction element 21 to the sensor output corresponding to the full scale value (registered value) is used as the sensor output value.
Further, temperature data and humidity data based on voltage values measured by the humidity measuring voltmeter 37 and the temperature measuring voltmeter 38 are input to the microcomputer 31 .
Furthermore, by supplying the test gas to the oxygen sensor 40 arranged on the same gas flow path as the heat conduction type gas sensor 10, the current value measured by the ammeter (not shown) is used as the oxygen sensor output for main control. It is input to the unit 50 . In the main control unit 50, the oxygen concentration contained in the test gas is calculated based on the oxygen sensor output from the oxygen sensor 40, and the oxygen concentration data thus obtained is used to drive the thermal conductivity gas sensor 10. It is output to the microcomputer 31 in the control section 30 .

In this gas detector, the gas concentration of the gas to be detected is calculated by the calibration curve method based on the sensor output value obtained by the thermal conductivity gas sensor 10. As shown in FIG. For 10 sensor output values,
[S1] Correction of temperature and humidity according to the measurement environmental temperature T ₂ [°C] and the measurement environmental humidity H ₂ [mg/L] of the measurement environment atmosphere,
[S2] Oxygen correction according to the oxygen concentration of the measurement environment atmosphere,
[S3] Temperature correction of the reference calibration curve data with a temperature amount correction amount according to the temperature difference between the reference temperature T ₁ [°C] and the measurement environment temperature T ₂ [°C];
[S4] Humidity correction of the gas concentration value is performed with a humidity correction amount corresponding to the amount of moisture contained in the test gas.

[S1] Temperature and Humidity Correction of Sensor Output Value In the temperature and humidity correction of the sensor output value, first, the temperature correction zero output value Ib _(T2) at the measurement environment temperature T ₂ [°C] is expressed by the following formula (1). It is calculated based on the zero calibration value Ib _(T1) at the reference temperature T ₁ [° C.] according to the temperature characteristics showing the correlation between the temperature of the selected base gas and the sensor output value. In addition, the temperature correction full scale value Is _(T2) at the measurement environment temperature T ₂ [°C] is set to the temperature indicating the correlation between the temperature of the selected detection target gas and the sensor output value, which is expressed by the following equation (2). It is calculated based on the full-scale value Is _(T1) of the selected detection target gas at the reference temperature T ₁ [° C.] depending on the characteristics. α _b1 and α _b2 in the following formula (1) are temperature correction coefficients corresponding to the selected base gas, and α _s1 and α _s2 in the following formula (2) are corresponding to the selected detection target gas. is the temperature correction factor.
formula (1)
Ib _(T2) = α _b1 × (T ₂ ² - T ₁ ² ) + α _b2 × (T ₂ - T ₁ ) + Ib _(T1)
formula (2)
Is _(T2) = α _s1 × (T ₂ ² - T ₁ ² ) + α _s2 × (T ₂ - T ₁ ) + Is _(T1)

Also, the temperature/humidity corrected zero output value Ib _(TH2) corresponding to the measured environmental humidity H ₁ [mg/L] is calculated as the correlation between the humidity of the selected base gas and the sensor output value shown by the following equation (3). is calculated based on the temperature-corrected zero output value Ib _(T2) according to the humidity characteristic showing Further, the temperature/humidity corrected full scale value Is _(TH2) at the measured environmental humidity H ₂ [mg/L] is calculated as the correlation between the humidity of the selected gas to be detected and the sensor output value as shown by the following equation (4). is calculated based on the temperature-corrected full-scale value Is _(T2) according to the humidity characteristic showing β _b1 and β _b2 in the following formula (3) are humidity correction coefficients according to the selected base gas, and β _s1 and β _s2 in the following formula (4) are according to the selected detection target gas. is the humidity correction factor.
Then, the full-scale span value in the temperature-humidity-corrected reference environment is obtained from the following equation (5).
Formula (3)
Ib _(TH2) = - (β _b1 × (H ₂ ² - H ₁ ² ) + β _b2 × (H ₂ - H ₁ )) + Ib _(T2)
Formula (4)
Is _(TH2) = - (β _b1 × (H ₂ ² - H ₁ ² ) + β _s2 × (H ₂ - H ₁ )) + Is _(T2)
Formula (5)
L _(TH2) = Is _(TH2) - Ib _(TH2)

Next, zero gas temperature correction is performed to correct the sensor output value Im obtained by the heat conduction type gas sensor 10 to the temperature corrected sensor output value Im _(T1) , which is the sensor output value at the reference temperature T ₁ [°C]. The amount of drift of the sensor output value Im due to temperature is compensated by the zero gas temperature correction. Specifically, the temperature corrected sensor output value Im _(T1) is calculated based on the sensor output value Im using the above equation (1).
Further, the temperature corrected sensor output value Im _(T1) thus obtained is corrected to the humidity corrected output value Im _(TH1) , which is the sensor output value corresponding to the reference humidity H ₁ [mg/L]. A humidity correction is performed to compensate for the amount of drift in the sensor output value due to humidity. Specifically, the humidity corrected output value Im _(TH1) is calculated based on the temperature corrected sensor output value Im _(T1) using the above equation (3).
A span value L _{(TH1) (} =Im _(TH1) -Ib _(T1) ) of the zero gas reference humidity corrected output value Im(TH1) thus obtained is calculated.

As described above, the temperature characteristics of the base gas and the detection target gas differ from each other, and the humidity characteristics of the base gas and the detection target gas differ from each other, so the temperature and humidity characteristics of the detection target gas were corrected. We need to obtain the span value L _(TH3) . Specifically, the span value L _(TH3) corrected for temperature and humidity characteristics is calculated by the following formula (6). In the following formula (6), L _(TH2) is the span value (= full scale value Is _(T1) - zero calibration value Ib _{(T1 )} ), L _(TH2) /L _(T2) indicates the degree of fluctuation due to the temperature of the base gas, and L _(TH2) /L _(H2) indicates the degree of fluctuation due to the humidity of the base gas.
Formula (6)
L _(TH3) = L _(TH1) × (L _(TH2) /L _(T2) ) × (L _(TH2) /L _(H2) )

Here, the above L _(T2) and L _(H2) are represented by the following formulas (7) and (8).
Formula (7)
L _(T2) = L _(TH1) - (α _s1 - α _b1 ) x (T ₁ - T ₂ ) - (α _s2 - α _b2 ) x (T ₁ - T ₂ )
Formula (8)
L _(H2) = L _(TH1) - (β _s1 - β _b1 ) x (H ₁ - H ₂ ) - (β _s2 - β _b2 ) x (H ₁ - H ₂ )

[S2] Oxygen Correction of Sensor Output Value Oxygen correction of sensor output is a process of correcting floating of the zero point with respect to a base gas such as nitrogen gas or inert gas.
In oxygen correction of the sensor output, the ratio of oxygen and nitrogen contained in the base gas is obtained based on the oxygen concentration value obtained by the oxygen sensor 40, and the span value L _{(TH3 )} is corrected by a correction amount corresponding to the oxygen concentration in the measurement gas to obtain the primary correction sensor output value Im _(THO) , thereby obtaining the span value L _(THO) . By performing the oxygen correction, the amount of drift of the sensor output due to the oxygen concentration is compensated. The correction amount is calculated based on the correlation between the sensor output value of the heat conduction type gas sensor 10 and the oxygen concentration contained in the base gas, which has been acquired in advance.

(S3) Temperature correction of calibration curve data The span value L _(THO) obtained as described above is applied to the reference calibration curve data corresponding to the selected base gas of the selected detection target gas in the reference environment. A gas concentration value R _(TH1) is obtained by comparison.
By correcting this gas concentration value R _(TH1) with a temperature amount correction value corresponding to the temperature difference between the measurement environment temperature T ₂ [°C] and the reference temperature T ₁ [°C], the temperature corrected gas concentration value R _(T2) is obtained. to get Specifically, the temperature correction gas concentration value R _(T2) is calculated by subtracting the temperature amount correction value C _T obtained by the following equation (9) from the gas concentration value R _(TH1) . γ in the following formula (6) is a temperature amount correction coefficient according to the gas to be detected.
formula (9)
C _T =γ×[{50/((|R _(TH1) −50|)+50)}−0.5]×(T ₂ −T ₁ )

The calibration curve data is obtained based on the calibration curve data at the reference temperature because the output characteristics of the calibration curve data differ depending on the temperature and, for example, the average concentration change rate in the temperature range between two temperature values varies depending on the gas concentration value. The gas concentration value R _(TH1) is the gas concentration value R _(TH1) , the temperature amount correction coefficient γ corresponding to the gas to be detected, and the temperature difference (T ₂ -T ₁ ) between the measurement environment temperature and the reference temperature. Temperature correction is performed in a state in which the degree of influence of the gas concentration value R _(TH1) on the correction amount is compensated by the correction with the temperature amount correction value C _T determined by .

(S4) Humidity correction using the humidity correction _value according to the amount of moisture contained in the test gas. The final gas concentration instruction value R is acquired by correcting with the humidity amount correction value. Specifically, the gas concentration instruction value R is calculated by subtracting the humidity amount correction value C _M obtained by the following equation (10) from the temperature correction gas concentration value R _(T2) . In the following equation (10), δ is a humidity amount correction coefficient corresponding to the gas to be detected, and M is the volume fraction [vol%] of the humidity in the measurement environment atmosphere.
Formula (10)
C _M = δ x (R _(T2) /100) x M

The temperature-corrected gas concentration value R _{(T2) obtained by temperature-correcting the gas concentration value R (TH1) based} on the calibration curve data at the reference temperature is the temperature-corrected gas concentration value R _(T2) and the detection target gas. and the humidity amount correction value C _M determined by the moisture amount contained in the test gas. ing.

As described above, in the above-described gas detector, the temperature correction and humidity correction of the sensor output of the heat conduction type gas sensor 10 are performed using correlation formulas corresponding to the detection target gas type and the base gas type, respectively. , the influence of the detection target gas species and the influence of the base gas species are compensated. Further, since the floating of the zero point with respect to the base gas is corrected by performing the oxygen correction according to the oxygen concentration in the measurement environment atmosphere, the influence due to the oxygen concentration is compensated. Furthermore, the degree of influence of the gas concentration value on the temperature correction value is compensated by performing the temperature correction of the reference calibration curve data. Moreover, since the humidity amount correction is performed according to the humidity amount of the measurement environment atmosphere, excessive correction of the influence of the humidity on the reference calibration curve data can be avoided. Therefore, it is possible to accurately correct the sensor output of the heat conduction type gas sensor 10 according to the environmental conditions of the measurement environment atmosphere, and to perform gas concentration detection with high accuracy.

Although the embodiments of the gas detector of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.
For example, although the gas detector in the above embodiment is configured to include an oxygen sensor, it may be configured such that the oxygen concentration of the atmosphere to be measured is externally input to the main control unit. , the gas detector itself need not be configured to include an oxygen sensor.
In addition, in the above-described heat conduction type gas sensor, the heat conduction element and the temperature/humidity detection element are provided in a common casing. Therefore, the gas detector may have a configuration in which a temperature and humidity sensor is provided separately from the heat conduction type gas sensor.
In the above embodiment, the gas concentration value obtained from the calibration curve data is subjected to temperature correction and humidity amount correction to obtain the final gas concentration indicated value. After performing temperature correction and humidity amount correction on the calibration curve data, the gas concentration value may be obtained based on the corrected calibration curve data.
Moreover, the reference temperature and the reference humidity as the reference environment can be set as appropriate, and a plurality of reference temperatures and reference humidity may be set.

Experimental examples conducted to confirm the effects of the present invention will be described below.

<Experimental example 1>
Using the gas detector manufactured according to the configuration shown in FIGS. The gas concentration was measured while appropriately changing the temperature and humidity of the chamber. When calculating the gas concentration, the temperature and humidity correction (S1) and oxygen correction (S2) are performed on the sensor output value obtained from the heat conduction type gas sensor, and the calibration curve data with a reference temperature of 20°C and a reference humidity of 0 mg/L is used. there was. The temperature of the test gas was adjusted within the temperature range of −20° C. to 60° C., and the humidity was adjusted within the range of 0.00 mg/L to 80.00 mg/L.
When the error of the measured gas concentration value with respect to the true value was examined, it was found that the gas concentration could be measured within an error range of -3.0 to +5.0% regardless of the temperature and humidity of the test gas. confirmed.

<Experimental example 2>
Gas concentrations were measured in the same manner as in Experimental Example 1, except that calibration curve data temperature correction (S3) was performed in calculating the gas concentrations.
When the error of the measured gas concentration value with respect to the true value was examined, the gas concentration could be measured within an error range of -2.0 to +4.0%, and the reliability of gas concentration detection could be improved. confirmed to be possible.

<Experimental example 3>
Gas concentrations were measured in the same manner as in Experimental Example 1, except that calibration curve data temperature correction (S3) and humidity amount correction (S4) were further performed in the gas concentration calculation in Experimental Example 1 above.
When the error of the measured gas concentration value with respect to the true value was examined, the gas concentration could be measured within an error range of -1.0 to +1.0%, further improving the reliability of gas concentration detection. was confirmed to be possible.

<Comparative Experimental Example 1>
In Experimental Example 1, the gas concentration was measured in the same manner as in Experimental Example 1, except that only the temperature and humidity correction (S1) was performed when calculating the gas concentration, and the oxygen correction (S2) was not performed.
When the error of the measured gas concentration value with respect to the true value was investigated, it was confirmed that the error was +10% at the maximum, and it was not suitable for practical use.

REFERENCE SIGNS LIST 10 heat conduction type gas sensor 11 casing 11a gas introduction port 12 air-permeable sheet 13 sintered wire mesh 14 sealing material 15 substrate 16 stud 17 heat conduction element housing member 18 ventilation path 19 recess 19a ventilation port 20 detector 21 heat conduction element 22 Coating film 23 Resistance heating element 25 Temperature/humidity detection element 30 Thermal conduction type gas sensor drive controller 31 Microcomputer 32 Heat conduction element drive circuit 33 Heat conduction element power supply 34 Ammeter 35 Temperature/humidity detection element drive circuit 36 Temperature/humidity detection Element power supply 37 Humidity measurement voltmeter 38 Temperature measurement voltmeter 40 Oxygen sensor 41 Oxygen sensor element 42 Oxygen sensor element drive circuit section 43 Oxygen sensor element power supply 45 Oxygen sensor drive control section 50 Main control section S Storage room

Claims (4)

A gas detector comprising a thermal conductivity gas sensor,
The heat conduction type gas sensor has a heat conduction element and a heat conduction type gas sensor drive control unit that controls the operation of the heat conduction element,
The thermal conduction type gas sensor drive control unit controls the sensor output obtained for the gas to be measured in the atmosphere of the measurement environment to vary depending on the temperature difference between the reference temperature and the measurement environment temperature and the humidity difference between the reference humidity and the measurement environment humidity. It has a function of performing temperature and humidity correction to correct fluctuations and oxygen correction according to the oxygen concentration of the measurement environment atmosphere,
In the temperature/humidity correction, the sensor output value obtained by the heat conduction element is determined by the reference temperature and the measurement environment temperature according to a correlation formula using a temperature correction coefficient according to the type of gas to be detected and the type of base gas. The temperature is corrected based on the temperature difference between
A gas detector, wherein the temperature-corrected sensor output value obtained by the temperature correction is subjected to humidity correction by a correlation formula using a humidity correction coefficient corresponding to the type of gas to be detected and the type of base gas. The thermal conductivity type gas sensor drive control unit converts the primary corrected sensor output value obtained by performing the temperature/humidity correction and the oxygen correction to the reference calibration curve for the detection target gas at the reference temperature and the reference humidity. configured to obtain a gas concentration value of the gas to be sensed by comparing it to the data;
The thermal conductivity type gas sensor drive control unit further has a function of performing calibration curve data temperature correction for correcting variations in the reference calibration curve data due to a temperature difference between the reference temperature and the measurement environment temperature,
In the calibration curve data temperature correction, the gas concentration value is a temperature determined by the gas concentration value, a temperature amount correction coefficient corresponding to the gas to be detected, and the temperature difference between the reference temperature and the measurement environment temperature. 2. A gas detector as claimed in claim 1, characterized in that it is corrected with a quantity correction value. The thermal conductivity type gas sensor drive control unit further has a function of performing humidity amount correction for correcting variations in the temperature-corrected gas concentration value obtained by performing the calibration curve data temperature correction due to the humidity amount of the measurement environment atmosphere. death,
In the humidity amount correction, the temperature-corrected gas concentration value is a humidity amount correction determined by the temperature-corrected gas concentration value, a humidity amount correction coefficient corresponding to the gas to be detected, and the amount of water contained in the gas to be detected. 3. A gas detector according to claim 2, characterized in that it is corrected with a value. 4. The gas detector according to any one of claims 1 to 3, wherein the type of gas to be detected and the type of base gas are selectable.

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