Gas detector

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

[Technical Field]

[0001] The present invention relates to a gas detector equipped with a thermal conduction type gas sensor. [Background technology]

[0002] Currently, a thermal conduction gas sensor is known as one of the gas sensors for detecting, for example, combustible gases, which detects the change in thermal conductivity of the gas to be detected as the concentration of the gas to be detected.Thermal conduction gas sensors are suitable for detecting, for example, high-concentration combustible gases exceeding 100% LEL, or combustible gases with an oxygen concentration of 10% or less. A thermal conduction gas sensor has a heat conduction element made of, for example, a metal coil. When a target gas contacts this heat conduction element while electricity is applied, the state of heat dissipation changes due to the thermal conductivity specific to the target gas, which in turn changes the temperature of the heat conduction element. As the temperature of the heat conduction element changes, the resistance value of the metal coil that constitutes the heat conduction element changes, and the concentration of the target gas is measured based on the amount of change in this resistance value.

[0003] In a thermal conduction gas sensor, the sensor output fluctuates (drifts) depending on the temperature and humidity of the measurement environment. For this reason, a thermal conduction gas sensor has been proposed that is provided with a temperature detection unit and a humidity detection unit and configured to correct the fluctuation in sensor output due to the temperature and humidity of the measurement environment (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-194409 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the case of thermal conduction gas sensors, it has become clear that fluctuations in the sensor output cannot be adequately compensated for simply by performing temperature and humidity corrections on the sensor output, making it difficult to detect gas concentrations with high accuracy.

[0006] The present invention was completed in consideration of the above circumstances, and its object is to provide a gas detector that can accurately correct the sensor output of a thermal conduction gas sensor in accordance with the environmental conditions of the measurement atmosphere, thereby enabling highly accurate gas concentration detection. [Means for solving the problem]

[0007] The gas detector of the present invention is a gas detector equipped with a thermal conduction gas sensor, the thermal conduction gas sensor having a thermal conduction element and a thermal conduction gas sensor drive control unit that controls the operation of the thermal conduction element. The thermal conduction gas sensor drive control unit performs temperature and humidity correction on the sensor output obtained for the gas to be detected in the measurement environment atmosphere to correct for fluctuations due to the temperature difference between a reference temperature and the measurement environment temperature and fluctuations due to the humidity difference between the reference humidity and the measurement environment humidity, and also performs oxygen correction in accordance with the oxygen concentration in the measurement environment atmosphere. In the temperature and humidity correction, the sensor output value obtained by the thermal conduction element is temperature-corrected based on the temperature difference between the reference temperature and the measurement environment temperature using a correlation equation that uses temperature correction coefficients according to the type of gas to be detected and the type of base gas, and the temperature-corrected sensor output value obtained by the temperature correction is humidity-corrected using a correlation equation that uses humidity correction coefficients according to the type of gas to be detected and the type of base gas, thereby solving the above-mentioned problems. [Effects of the Invention]

[0008] According to the invention of claim 1, the temperature and humidity corrections of the sensor output of the thermal conduction gas sensor are performed using correlation equations corresponding to the target gas species and base gas species, respectively, thereby compensating for the influence of the target gas species and base gas species. Moreover, oxygen correction according to the oxygen concentration in the measurement environment atmosphere is performed, thereby correcting the zero point floating relative to the base gas, thereby compensating for the influence of the oxygen concentration. 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 highly accurate gas concentration detection.

[0009] According to the invention of claim 2, the temperature correction of the gas concentration value is performed in a state where the degree of influence on the correction amount due to the gas concentration value obtained based on the reference calibration curve data is compensated for, thereby further improving the accuracy of the correction of the sensor output.

[0010] According to the invention of claim 3, excessive correction of the influence of humidity on the reference calibration curve data can be avoided, and therefore the accuracy of correction of the sensor output can be further improved.

[0011] According to the invention of claim 4, the fluctuation in sensor output due to differences in base gas is compensated for, thereby improving the accuracy of gas concentration detection. In addition, if an oxygen sensor is provided, the calibration process of the thermal conduction gas sensor can be efficiently performed, including the calibration process of the oxygen sensor. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a block diagram showing an outline of the configuration of an example of a gas detector of the present invention. [Figure 2] FIG. 1 is an explanatory cross-sectional view showing an example of the configuration of a thermal conduction type gas sensor. [Figure 3] 3A and 3B are explanatory views showing the configuration of a heat conduction element in the heat conduction gas sensor shown in FIG. 2, where FIG. 3A is a perspective view and FIG. 3B is a cross-sectional view cut in a direction perpendicular to the longitudinal direction. [Figure 4]FIG. 10 is an operational flow diagram showing an example of a correction process for a sensor output. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the gas detector of the present invention will be described. 1 is a block diagram showing an outline of the configuration of an example of a gas detector of the present invention. This gas detector comprises a thermal conduction gas sensor 10, an oxygen sensor 40, and a main control unit 50.

[0014] The thermal conduction gas sensor 10 in this embodiment includes a detection unit 20 having a heat conduction element 21 and a temperature and humidity detection element 25, and a thermal conduction gas sensor drive control unit 30 that controls the operation of the heat conduction element 21 and the temperature and humidity detection element 25.

[0015] 2 is an explanatory cross-sectional view showing an example of the configuration of a thermal conduction gas sensor. This thermal conduction gas sensor 10 has a cylindrical casing 11. An opening at one end (the upper end in FIG. 2) of this casing 11 serves as a gas inlet 11a for introducing a gas to be detected into the casing 11. Within the casing 11, a substantially circular substrate 15 is disposed along a plane perpendicular to the axial direction of the casing 11. A temperature and humidity detection element 25 for measuring the temperature and humidity of the gas to be detected and a plurality of studs 16 are mounted on this substrate 15.

[0016] Disk-shaped heat conducting element housing member 17 that houses heat conducting element 21 is disposed on substrate 15. Heat conducting element housing member 17 is made of an insulating and heat-resistant resin material, for example, polyphenylene sulfide (PPS) resin containing fibers such as glass fibers. A recess 19 is formed on the surface (top surface in FIG. 2) of heat conducting element housing member 17 to form housing chamber S in which heat conducting element 21 is housed, and the opening of recess 19 serves as vent port 19a for introducing test gas into housing chamber S. Heat conducting element 21 is electrically connected to two conductive pins extending in the thickness direction of heat conducting element housing member 17. Furthermore, in the heat conducting element housing member 17, an air passage 18 for introducing the gas to be detected into the temperature and 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. By configuring the temperature and humidity detection element 25 to be arranged in a space isolated from the space (storage chamber S) in which the heat conduction element 21 is arranged (thermally isolated configuration), temperature data and humidity data of the test gas can be obtained without being affected by the heat conduction element 21.

[0017] A circular breathable sheet 12 is placed on the surface of the heat conducting element housing member 17 so as to cover the vent hole 19a and the opening of the ventilation path 18. The breathable sheet 12 can be made of a material such as glass wool. A circular sintered wire mesh 13 made of, for example, stainless steel (SUS316) is placed on the breathable sheet 12 with its peripheral edge fixed to the inner wall surface of the casing 11, and the breathable sheet 12 is sandwiched between the sintered wire mesh 13 and the heat conduction element storage member 17. Also, below the substrate 15 within the casing 11, a sealant 14 made of a cured adhesive such as an epoxy resin adhesive is provided so as to close the opening on the lower side of the casing 11.

[0018] As shown in FIGS. 3(a) and 3(b), heat conducting element 21 is configured, for example, by winding resistance heating element 23 having coating film 22 on its surface 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 that is inactive to the target gas, such as gold. The thickness of the coating film 22 is, for example, 100 nm. The coating film 22 can be formed by an appropriate thin film formation method, such as sputtering. In an example configuration of heat conducting element 21, resistance heating element 23 has a wire diameter of φ15 to 30 μm, a coil length of 0.3 to 1.2 mm, a coil diameter of 0.2 to 0.4 mm, and 8 to 12 turns of the coil.

[0019] The temperature and humidity detecting element 25 is, for example, an electrical resistance change type that detects the temperature and relative humidity of the test gas by measuring the resistance change that occurs upon contact with the gas. The temperature and humidity detecting element 25 may also be a capacitance type, and is not particularly limited as long as it can detect the temperature and relative humidity of the test gas.

[0020] The thermal conduction type gas sensor drive control unit 30 includes a microcomputer 31, a thermal conduction element drive circuit unit 32, and a temperature and humidity detection element drive circuit unit . Heat conducting element drive circuit 32 includes a heat conducting element power supply 33 that supplies electricity to heat conducting element 21 and an ammeter 34 that measures the current flowing through heat conducting element 21 . The temperature and humidity detection element drive circuit 35 includes a power supply 36 for the temperature and humidity detection element, a humidity measurement voltmeter 37, and a temperature measurement voltmeter 38. The microcomputer 31 has a function of correcting the sensor output acquired by the heat conduction element 21 according to the temperature, humidity, base gas type, and oxygen concentration of the measurement environment atmosphere to calculate the concentration of the target gas. Unless otherwise specified, in this specification, "humidity" refers to absolute humidity, and therefore, when correcting the sensor output, the absolute humidity value calculated from the relative humidity value and temperature value acquired by the temperature and humidity detection element 25 is used.

[0021] The microcomputer 31 also stores data related to output correction of the thermal conduction gas sensor 10, such as the zero calibration value in the reference environment (reference temperature T1 [°C], reference humidity H1 [mg / L]) and the full-scale value of each type of target gas (concentration 100 vol%), the temperature and humidity characteristics of each type of target gas at a concentration of 100 vol%, the temperature and humidity characteristics of each type of base gas, the temperature correction coefficient according to the base gas type and the target gas type, the humidity correction coefficient according to the base gas type and the target gas type, the reference calibration curve data according to the base gas of each type of target gas in the reference environment, and the temperature correction value and humidity correction value of the reference calibration curve data. This gas detector is configured to allow selection of the target gas type and base gas type, and the output of the thermal conduction gas sensor 10 for the selected target gas is corrected according to the base gas type, thereby compensating for fluctuations in sensor output due to differences in base gas type. The gas species to be detected are, for example, methane gas (CH4), isobutane gas (i-C4H 10 ), paraffinic hydrocarbon gases such as propane gas, hydrogen gas, and other flammable gases can be selected. The base gas species can be selected from, for example, nitrogen gas (N2) and an inert gas, which is an inert mixed gas of nitrogen, carbon dioxide, and oxygen.

[0022] The oxygen sensor 40 includes, for example, a galvanic cell-type oxygen sensor element 41, an oxygen sensor element drive circuit unit 42 equipped with a power supply 43 for the oxygen sensor element and an ammeter (not shown), and an oxygen sensor drive control unit 45 that controls the operation of the oxygen sensor element 41.

[0023] The main control unit 50 has a function of outputting operation command signals to the thermal conduction gas sensor 10 and the oxygen sensor 40, and also controls the operations of other components of the gas detector. It also has the function of calculating the oxygen concentration contained in the test gas in the measurement environment atmosphere based on the sensor output from the oxygen sensor 40 and outputting the result to the microcomputer 31 in the thermal conduction type gas sensor drive control unit 30 of the thermal conduction type gas sensor 10.

[0024] The gas concentration calculation function of the thermal conduction type gas sensor drive control unit 30, that is, the output correction of the thermal conduction type gas sensor 10, will be described below. First, in the gas detector, a warm-up process is performed to stabilize the zero point before gas detection. The warm-up process is performed by applying a voltage to the heat-conducting element 21 that is lower than the voltage applied to the heat-conducting element 21 during measurement for a predetermined time.

[0025] After the warm-up process, the thermal conduction gas sensor drive control unit 30 applies a voltage controlled to an appropriate magnitude to the heat conduction element 21 in response to an operation command signal from the main control unit 50, thereby heating the heat conduction element 21 so that its surface temperature is maintained at a predetermined temperature. In this state, a test gas in the measurement environment is supplied to the thermal conduction gas sensor 10, and the test gas comes into contact with the heat conduction element 21, causing a change in thermal conductivity (resistance change) of the heat conduction element 21. This change is measured as a current value by the ammeter 34 and input as a sensor output to the microcomputer 31 of the thermal conduction gas sensor drive control unit 30. For sensor output correction, the output ratio of the sensor output acquired 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. Furthermore, 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, when the test gas is supplied to the oxygen sensor 40, which is arranged on the same gas flow path as the thermal conduction gas sensor 10, a current value measured by an ammeter (not shown) is input as an oxygen sensor output to the main control unit 50. The main control unit 50 calculates the oxygen concentration contained in the test gas based on the oxygen sensor output from the oxygen sensor 40, and outputs the oxygen concentration data thus obtained to the microcomputer 31 in the thermal conduction gas sensor drive control unit 30 of the thermal conduction gas sensor 10.

[0026] 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 acquired by the thermal conduction gas sensor 10. As shown in FIG. 4, the following is performed with respect to the sensor output value of the thermal conduction gas sensor 10: [S1] Temperature and humidity correction according to the measurement environment temperature T2 [℃] and measurement environment humidity H2 [mg / L] of the measurement environment atmosphere, [S2] Oxygen correction according to the oxygen concentration in the measurement environment atmosphere, [S3] Temperature correction of the reference calibration curve data using a temperature correction amount according to the temperature difference between the reference temperature T1 [°C] and the measurement environment temperature T2 [°C]. [S4] Humidity correction of gas concentration value using a humidity correction amount according to the amount of moisture contained in the detected gas will be carried out.

[0027] [S1] Temperature and humidity correction of sensor output values In temperature and humidity correction of the sensor output value, first, the temperature correction zero output value Ib at the measurement environment temperature T2 [℃] (T2) The zero calibration value Ib at the reference temperature T1 [°C] is calculated using the temperature characteristic that shows the correlation between the temperature of the selected base gas and the sensor output value, as shown in the following formula (1). (T1) The temperature-corrected full-scale value Is at the measurement environment temperature T2 [°C] is calculated based on (T2) The full-scale value Is of the selected target gas at the reference temperature T1 [°C] is calculated by the temperature characteristic that shows the correlation between the temperature of the selected target gas and the sensor output value, as shown in the following formula (2). (T1) Calculation is based on the following formula (1): b1 and α b2 is a temperature correction coefficient according to the selected base gas, and is expressed as α in the following formula (2): s1 and α s2 is a temperature correction coefficient according to the selected target gas. Formula (1) Ib (T2) =α b1 ×(T2 2 -T1 2 )+α b2 ×(T2-T1)+Ib (T1) Formula (2) Is (T2) =α s1 ×(T2 2 -T1 2 )+α s2 ×(T2-T1)+Is (T1)

[0028] In addition, the temperature and humidity corrected zero output value Ib according to the measurement environment humidity H1 [mg / L] (TH2) The temperature-corrected zero output value Ib is calculated by the humidity characteristic that shows the correlation between the humidity of the selected base gas and the sensor output value, as shown in the following equation (3). (T2)Furthermore, the temperature and humidity corrected full scale value Is at the measurement environment humidity H2 [mg / L] (TH2) The temperature-corrected full-scale value Is is calculated by the humidity characteristic that shows the correlation between the humidity of the selected detection target gas and the sensor output value, as shown in the following equation (4). (T2) β in the following formula (3) is calculated based on b1 and β b2 is a humidity correction coefficient according to the selected base gas, and is expressed as β in the following equation (4): s1 and β s2 is the humidity correction coefficient according to the selected target gas. Then, the full-scale span value in the temperature and humidity corrected reference environment is obtained from the following equation (5). Formula (3) Ib (TH2) =-(β b1 ×(H2 2 -H1 2 )+β b2 ×(H2-H1))+Ib (T2) Formula (4) Is (TH2) =-(β b1 ×(H2 2 -H1 2 )+β s2 ×(H2-H1))+Is (T2) Formula (5) L (TH2) =Is (TH2) -Ib (TH2)

[0029] Next, the sensor output value Im obtained by the thermal conduction gas sensor 10 is converted into a temperature-corrected sensor output value Im, which is the sensor output value at the reference temperature T1 [°C]. (T1) By performing zero gas temperature correction, the amount of drift of the sensor output value Im due to temperature is compensated for. Specifically, the temperature-corrected sensor output value Im (T1) is calculated based on the sensor output value Im using the above formula (1). The temperature-corrected sensor output value Im obtained in this way (T1)The humidity corrected output value Im is the sensor output value according to the reference humidity H1 [mg / L]. (TH1) This compensates for the drift of the sensor output value due to humidity. (TH1) Using the above equation (3), the temperature-corrected sensor output value Im (T1) Calculated based on the following. The humidity-corrected output value Im obtained based on the zero gas (TH1) Span value L (TH1) (=Im (TH1) -Ib (T1) ) is calculated.

[0030] As described above, the temperature characteristics of the base gas and the temperature characteristics of the gas to be detected are different from each other, and the humidity characteristics of the base gas and the humidity characteristics of the gas to be detected are also different from each other. Therefore, the span value L (TH3) Specifically, the span value L corrected for temperature and humidity characteristics is (TH3) is calculated by the following formula (6). In the following formula (6), L (TH2) is the span value (= full scale value Is) when the concentration of the selected detection target gas in the reference environment is 100 vol%. (T1) -Zero calibration value Ib (T1) ) and L (TH2) / L (T2) is the degree of variation due to the base gas temperature, L (TH2) / L (H2) indicates the degree of variation due to the humidity of the base gas. Formula (6) L (TH3) =L (TH1) ×(L (TH2) / L (T2) )×(L (TH2) / L (H2) )

[0031] Here, the above L (T2) and L (H2) are expressed by the following formulas (7) and (8). Formula (7) L (T2) =L (TH1) -(α s1 -αb1 ) × (T1-T2)-(α s2 -α b2 )×(T1-T2) Formula (8) L (H2) =L (TH1) -(β s1 -β b1 ) × (H1-H2)-(β s2 -β b2 )×(H1-H2)

[0032] [S2] Oxygen correction of sensor output value Oxygen correction of the sensor output is a process for correcting the zero point floating relative to a base gas such as nitrogen gas or an inert gas. In the oxygen correction of the sensor output, the ratio of oxygen and nitrogen contained in the base gas is calculated based on the oxygen concentration value acquired by the oxygen sensor 40, and the span value L corrected for the temperature and humidity characteristics of the gas to be detected is calculated. (TH3) is corrected by a correction amount according to the oxygen concentration in the measurement gas to obtain the primary corrected sensor output value Im (THO) Get the span value L (THO) By performing oxygen correction, the amount of drift in the sensor output due to the oxygen concentration is compensated for. The amount of correction is calculated based on the correlation between the sensor output value of the thermal conduction gas sensor 10, which has been acquired in advance, and the oxygen concentration contained in the base gas.

[0033] (S3) Temperature correction of calibration curve data The span value L obtained in this way (THO) The gas concentration value R is calculated by comparing the selected target gas in the reference environment with the standard calibration curve data corresponding to the selected base gas. (TH1) Get. This gas concentration value R (TH1) The temperature-corrected gas concentration value R is calculated by correcting the temperature correction value according to the temperature difference between the measurement environment temperature T2 [℃] and the reference temperature T1 [℃]. (T2) Specifically, the temperature-corrected gas concentration value R (T2) is the temperature correction value C calculated by the following formula (9). T The gas concentration value R (TH1)In the following formula (6), γ is a temperature correction coefficient according to the gas to be detected. Formula (9) C T =γ×〔{50 / ((|R (TH1) -50|)+50)}-0.5×(T2-T1)

[0034] The output characteristics of the calibration curve data vary depending on the temperature. For example, the average concentration change rate in the temperature range between two temperature values varies depending on the gas concentration value. Therefore, the gas concentration value R obtained based on the calibration curve data at the reference temperature (TH1) is the gas concentration value R (TH1) and a temperature quantity correction coefficient γ corresponding to the gas to be detected, and a temperature quantity correction value C determined by the temperature difference (T2-T1) between the measurement ambient temperature and the reference temperature. T By correcting this, the gas concentration value R (TH1) The temperature correction is performed in a state where the degree of influence of the temperature on the correction amount is compensated for.

[0035] (S4) Humidity correction using a humidity correction value according to the amount of moisture contained in the test gas The temperature-corrected gas concentration value R obtained in this way (T2) is corrected with a humidity correction value corresponding to the humidity of the measurement environment atmosphere to obtain the final gas concentration indication value R. Specifically, the gas concentration indication value R is obtained by correcting the humidity correction value C M The temperature-corrected gas concentration value R (T2) In the following formula (10), δ is a humidity correction coefficient according to the gas to be detected, and M is the volume fraction [vol%] of humidity in the measurement environment atmosphere. Formula (10) C M =δ×(R (T2) / 100)×M

[0036] Gas concentration value R based on calibration curve data at the reference temperature (TH1) The temperature-corrected gas concentration value R obtained by temperature-correcting (T2) is the temperature-corrected gas concentration value R (T2)and a humidity correction coefficient δ corresponding to the gas to be detected and a humidity correction value C determined by the amount of moisture contained in the gas to be detected. M By correcting this, it is possible to avoid excessive correction of the effects of humidity.

[0037] As described above, in the gas detector, the temperature and humidity corrections of the sensor output of the thermal conduction gas sensor 10 are performed using correlation equations corresponding to the target gas species and base gas species, respectively, thereby compensating for the influence of the target gas species and base gas species. Furthermore, oxygen correction according to the oxygen concentration in the measurement environment corrects the zero point floating relative to the base gas, thereby compensating for the influence of the oxygen concentration. Furthermore, temperature correction of the reference calibration curve data compensates for the degree of influence of the gas concentration value on the temperature correction value. Furthermore, humidity correction according to the humidity in the measurement environment prevents excessive correction of the influence of humidity on the reference calibration curve data. Therefore, the sensor output of the thermal conduction gas sensor 10 can be accurately corrected according to the environmental conditions of the measurement environment, allowing for highly accurate gas concentration detection.

[0038] Although the embodiments of the gas detector of the present invention have been described above, the present invention is not limited to the above-described embodiments and various modifications can be made. For example, the gas detector in the above embodiment is configured to include an oxygen sensor, but it may also be configured so that the oxygen concentration in the measurement environment atmosphere is externally input to the main control unit, and therefore the gas detector itself does not need to be configured to include an oxygen sensor. Furthermore, in the above-mentioned thermal conduction gas sensor, the thermal conduction element and the temperature and humidity detection element are configured to be provided in a common casing, but it is not necessary to configure the gas detector to include a temperature and humidity detection element. Therefore, the gas detector may be configured to include a temperature and humidity sensor separate from the thermal conduction gas sensor. In the above embodiment, the final gas concentration indication value is obtained by performing temperature correction and humidity correction on the gas concentration value obtained from the calibration curve data. However, it is also possible to perform temperature correction and humidity correction on the calibration curve data in the reference environment in advance, and then obtain the gas concentration value based on the corrected calibration curve data. Furthermore, the reference temperature and reference humidity as the reference environment can be set as appropriate, and a plurality of reference temperatures and reference humidities may be set.

[0039] Below, an example of an experiment conducted to confirm the effects of the present invention will be described.

[0040] <Experimental Example 1> Using a gas detector fabricated according to the configuration shown in Figures 1 to 3, gas concentration measurements were performed using isobutane gas, a test gas with a known gas concentration value, and an inert base gas (a mixture of nitrogen, carbon dioxide, and oxygen), while appropriately changing the temperature and humidity of the test gas. To calculate the gas concentration, temperature and humidity correction (S1) and oxygen correction (S2) were performed on the sensor output value obtained from the thermal conduction gas sensor, and calibration curve data with a reference temperature of 20°C and a reference humidity of 0 mg / L were used. 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 relative to the true value was investigated, it was confirmed 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.

[0041] <Experimental Example 2> Gas concentration measurements were carried out in the same manner as in Experimental Example 1 above, except that, in calculating the gas concentration, calibration curve data temperature correction (S3) was further carried out. When the error of the measured gas concentration value relative to the true value was investigated, it was confirmed that the gas concentration could be measured within an error range of -2.0 to +4.0%, thereby improving the reliability of gas concentration detection.

[0042] <Experimental Example 3> Gas concentration measurements were carried out in the same manner as in Experimental Example 1 above, except that calibration curve data temperature correction (S3) and humidity amount correction (S4) were further carried out when calculating the gas concentration. When the error of the measured gas concentration value relative to the true value was investigated, it was confirmed that the gas concentration could be measured within an error range of -1.0 to +1.0%, further improving the reliability of gas concentration detection.

[0043] <Comparative Experiment Example 1> In the above Experimental Example 1, gas concentration measurements were carried out in the same manner as in Experimental Example 1, except that in calculating the gas concentration, only temperature and humidity correction (S1) was performed, and oxygen correction (S2) was not performed. When the error of the measured gas concentration value relative to the true value was investigated, it was found that the error was up to +10%, making it unsuitable for practical use. [Explanation of symbols]

[0044] 10 Thermal conduction gas sensor 11 Casing 11a Gas inlet 12 Breathable sheet 13 Sintered wire mesh 14 Encapsulating material 15 PCB 16 studs 17 Heat conduction element housing material 18 Air passage 19 Recess 19a Ventilation hole 20 Detection unit 21 Heat conduction element 22 Coating membrane 23 Resistive heating element 25 Temperature and humidity detection element 30 Thermal conduction type gas sensor drive control unit 31 Microcomputer 32 Heat conduction element drive circuit section 33 Power supply for thermal conduction element 34 Ammeter 35 Temperature and humidity detection element drive circuit 36 Power supply for temperature and humidity detection element 37 Humidity measuring voltmeter 38 Temperature measuring voltmeter 40 Oxygen sensor 41 Oxygen sensor element 42 Oxygen sensor element drive circuit 43 Power supply for oxygen sensor element 45 Oxygen sensor drive control unit 50 Main control unit S Storage Room

Claims

1. A gas detector equipped with a thermal conduction type gas sensor, the thermal conduction type gas sensor includes 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 has a function of performing temperature and humidity correction on the sensor output acquired for the gas to be detected in the measurement environment atmosphere to correct for fluctuations due to a temperature difference between a reference temperature and the measurement environment temperature and fluctuations due to a humidity difference between the reference humidity and the measurement environment humidity, and also performing oxygen correction according to the oxygen concentration in the measurement environment atmosphere; In the temperature and humidity correction, the sensor output value acquired by the heat conduction element is temperature-corrected based on the temperature difference between the reference temperature and the measured ambient temperature using a correlation equation that uses a temperature correction coefficient corresponding to the type of gas to be detected and the type of base gas, and A gas detector characterized in that the temperature-corrected sensor output value obtained by the temperature correction is humidity-corrected using a correlation equation that uses humidity correction coefficients corresponding to the target gas species and base gas species.

2. the thermal conduction type gas sensor drive control unit is configured to acquire a gas concentration value of the target gas by comparing the primary corrected sensor output value acquired by performing the temperature and humidity correction and the oxygen correction with reference calibration curve data for the target gas at the reference temperature and the reference humidity; the thermal conduction type gas sensor drive control unit further has a function of performing calibration curve data temperature correction to correct fluctuations in the reference calibration curve data due to a temperature difference between the reference temperature and the measurement environment temperature; 2. The gas detector according to claim 1, wherein in the calibration curve data temperature correction, the gas concentration value is corrected by a temperature correction value determined by the gas concentration value, a temperature correction coefficient corresponding to the gas to be detected, and a temperature difference between the reference temperature and the measurement ambient temperature.

3. the thermal conduction type gas sensor drive control unit further has a function of performing humidity correction to correct fluctuations in the temperature-corrected gas concentration value acquired by performing temperature correction on the calibration curve data, due to the humidity of the measurement environment atmosphere; 3. The gas detector according to claim 2, wherein in the humidity correction, the temperature correction gas concentration value is corrected by a humidity correction value determined by the temperature correction gas concentration value, a humidity correction coefficient corresponding to the gas to be detected, and the amount of moisture contained in the gas to be detected.

4. 4. The gas detector according to claim 1, wherein the gas detector is configured to be capable of selecting the type of gas to be detected and the type of base gas.

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