Method for driving thermal conductivity gas sensor

Abstract

In this method for driving a thermal conductivity gas sensor, n thermal conductivity gas sensors each having a heater and a thermometer are driven, where n is an integer of 2 or greater. In the method for driving a thermal conductivity gas sensor, an operation for applying a plurality of voltages including a first voltage and a second voltage to the heater of each thermal conductivity gas sensor is periodically repeated so that the heater has a plurality of temperatures. In the method for driving the thermal conductivity gas sensor, the timing of application of the voltages to the heater of each thermal conductivity gas sensor is set so that the first voltage is applied to the heater of one thermal conductivity gas sensor at the timing when the second voltage is being applied to the heater of any of the thermal conductivity gas sensors.

Description

Method for driving a thermal conduction gas sensor

[0001] This disclosure relates to a method for driving a thermal conduction gas sensor.

[0002] A thermal conduction gas sensor, such as the one described in Patent Document 1, is widely used. A thermal conduction gas sensor comprises a heater and a thermometer. This sensor utilizes the differences in the inherent thermal conductivity of different gases to detect how much of a target gas, such as hydrogen, is present in a mixture of gases, such as air. When the concentration of hydrogen in the air changes, the thermal conductivity of the gas mixture changes, causing the heater to heat up and the temperature measured by the thermometer to change. Therefore, using a thermal conduction gas sensor, the concentration of the target gas can be calculated based on the temperature measured by the thermometer when the heater is heated.

[0003] Japanese Patent Publication No. 2025-14658

[0004] [Overview] In a heat conduction gas sensor, when measuring multiple temperatures with a thermometer, such as the temperature when the heater is turned on and the temperature when the heater is turned off, it is necessary to allow time for convergence to the target temperature. When measuring multiple temperatures in one cycle of heater on / off, if the cycle is shortened, the heater will not cool sufficiently when turned off, and the target temperature at the off time cannot be measured. Therefore, it is not possible to measure multiple temperatures in a cycle shorter than the predetermined time. If the heater is kept on all the time, the temperature at the off time cannot be measured and it will lead to deterioration of the wiring resistance.

[0005] The object of this disclosure is to provide a method for driving a thermal conduction gas sensor that can multiply the apparent measurement speed for measuring multiple temperatures by n, where n is an integer of 2 or more.

[0006] A first aspect of the present disclosure is a driving method for driving n thermal conduction gas sensors, each having a heater and a thermometer, where n is an integer of 2 or more, wherein the operation of applying a plurality of voltages, including a first voltage and a second voltage, to the heater of each thermal conduction gas sensor is periodically repeated so that the heater of each thermal conduction gas sensor reaches a plurality of temperatures, and the timing of applying the voltage to the heater of each thermal conduction gas sensor is set such that when the second voltage is applied to the heater of one of the n thermal conduction gas sensors, the first voltage is applied to the heater of another thermal conduction gas sensor among the n thermal conduction gas sensors.

[0007] A second aspect of the present disclosure is a sensor region that functions as a heat conduction gas sensor having a heater and a thermometer in each of n regions located at different positions within an insulating film, where n is an integer of 2 or more. The operation of applying a plurality of voltages, including a first voltage and a second voltage, to the heaters in each of the n sensor regions is periodically repeated so that the heaters in each of the n sensor regions reach a plurality of temperatures. The timing of applying the voltage to the heaters in each of the n sensor regions is set such that when the second voltage is applied to the heater in one of the n sensor regions, the first voltage is applied to the heater in another of the n sensor regions.

[0008] Figure 1 is a block diagram showing a control device for driving n thermal conduction gas sensors. Figure 2 is a cross-sectional view of a thermal conduction gas sensor. Figure 3 is a block diagram showing an example configuration of a thermal conduction gas sensor system that calculates the concentration of a target gas using thermal conduction gas sensors. Figure 4 is a cross-sectional view showing n thermal conduction gas sensors used in the driving method of the thermal conduction gas sensor according to the first embodiment. Figure 5 is a timing diagram showing an example of the timing of applying voltage to the heaters of n thermal conduction gas sensors according to the driving method of the thermal conduction gas sensor according to the first embodiment. Figure 6 is a timing diagram showing another example of the timing of applying voltage to the heaters of n thermal conduction gas sensors according to the driving method of the thermal conduction gas sensor according to the first embodiment. Figure 7 is a flowchart showing an example of the operation of a thermal conduction gas sensor system that drives n thermal conduction gas sensors to calculate gas concentration. Figure 8 is a top view showing a mounting component having n thermal conduction gas sensors used in the driving method of the thermal conduction gas sensor according to the second embodiment. Figure 9 is a cross-sectional view taken along line A-A in Figure 8. Figure 10 is a top view showing a mounting component having n thermal conduction gas sensors used in a driving method for a thermal conduction gas sensor according to the third embodiment. Figure 11 is a cross-sectional view taken along line B-B of Figure 10. Figure 12 is a cross-sectional view showing a mounting component having a thermal conduction gas sensor including n sensor regions used in a driving method for a thermal conduction gas sensor according to the fourth embodiment. Figure 13 is a cross-sectional view showing a modified example of the mounting component shown in Figure 12.

[0009] [Detailed Description] The following describes in detail the driving methods of several heat-conducting gas sensors according to multiple embodiments, with reference to the drawings. However, it should be noted that the drawings are schematic, and the relationship between thickness and planar dimensions, the ratio of thickness of each part, etc., may differ from those in reality. Furthermore, it is also true that there are parts where the dimensional relationships or ratios differ between drawings.

[0010] The embodiments described below are general or specific examples. The numerical values, shapes, materials, components, installation locations of components, and connection configurations shown in the following embodiments are examples only and are not intended to limit the scope of this disclosure. Furthermore, among the components in the following embodiments, those not described in the independent claim representing the highest-level concept will be described as optional components. In addition, the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from actual ratios. Furthermore, the following embodiments and their modifications may include similar components, and similar components will be given the same reference numerals, and redundant descriptions will be omitted.

[0011] <First Embodiment> As shown in Figure 1, the control device 10 drives the thermal conduction gas sensors 11 to 1n. n is an integer of 2 or more. Any of the thermal conduction gas sensors 11 to 1n is designated as thermal conduction gas sensor 1. The thermal conduction gas sensors 11 to 1n are sometimes collectively referred to as thermal conduction gas sensor 1. Hereafter, the thermal conduction gas sensor will be abbreviated as gas sensor. Hydrogen is one example of a gas to be detected.

[0012] Figure 2 shows the cross-sectional structure of the gas sensor 1. Insulating films 102, 103, and 104 are formed sequentially on the silicon (Si) substrate 101. The insulating films 102, 103, and 104 are made of silicon dioxide (SiO₂ ２ It consists of a laminate of ) and silicon nitride (SiN). In the insulating film 103, a platinum electrode 105 is placed between titanium oxide (TiO ｘ A heater 107 covered with a film 106 is provided. A thermometer 110 is provided in the insulating film 104, in which a platinum electrode 108 is covered with a titanium oxide film 109.

[0013] Figure 3 shows an example configuration of a thermal conduction type gas sensor system that calculates the concentration of the target gas using gas sensor 1. In Figure 3, for simplification, only one gas sensor 1 from the gas sensors 11 to 1n shown in Figure 1 is shown. The microcomputer 10M corresponds to the control device 10 shown in Figure 1. The temperature sensor IC (Integrated Circuit) 21 measures the ambient temperature and sets the measured temperature to I ２The power is supplied to the microcomputer 10M via the C (Inter Integrated Circuit) bus. The microcomputer 10M, for example, supplies +5V to the temperature sensor IC 21, the boost circuit 22, and the resistance measurement circuit 24.

[0014] The boost circuit 22, for example, boosts +5V to +15V and supplies it to the amplifier 23. The DAC (Digital-to-Analog Converter) of the microcomputer 10M supplies a voltage, for example +3V, to the amplifier 23 to be applied to the heater 107. The amplifier 23 boosts the voltage applied to the heater 107 and applies it to the heater 107. The amplifier 23 may be omitted.

[0015] The measurement data from the four terminals measured by the thermometer 110 is supplied to the resistance measurement circuit 24. The resistance measurement circuit 24 applies a current of 1 mA to the thermometer 110, for example, and measures the potential difference between the measurement data from the four terminals. The microcomputer 10M and the resistance measurement circuit 24 communicate with each other using SPI (Serial Peripheral Interface) communication. The microcomputer 10M calculates the resistance of the thermometer 110 by dividing the potential difference measured by the resistance measurement circuit 24 by the current supplied by the resistance measurement circuit 24 to the thermometer 110. The resistance measurement circuit 24 may be composed of an IC.

[0016] For example, if the heater 107 is turned on and heated by applying a predetermined voltage, the temperature is T, and the ambient temperature measured by the temperature sensor IC 21 is T. ０ The resistance value of the electrodes of the thermometer 110 at temperature T when a predetermined voltage is applied to the heater 107 is R. Ｔ , environmental temperature T ０ The resistance value of the electrode of the thermometer 110 is R Ｔ０ Let α be the thermal resistance coefficient. The microcomputer 10M calculates the temperature T using the following equation (1). The microcomputer 10M can similarly calculate the temperature when the heater 107 is turned off.

[0017]

[0018] The thermal conduction gas sensor system calculates the hydrogen concentration in the air by comparing the temperature T of air without hydrogen with the temperature T of air with hydrogen mixed in.

[0019] In the thermal conduction gas sensor system shown in Figure 3, the parts other than the gas sensor 1 may be composed of an ASIC (Application Specific Integrated Circuit). The control device 10 that drives the n gas sensors 1 may be composed of a microcomputer 10M, a PLC (Programmable Logic Controller), or an integrated circuit of an ASIC. The configuration of the control device 10 is arbitrary.

[0020] Figure 4 shows a cross-sectional view of n gas sensors 1 used in the driving method of the thermal conduction type gas sensor according to the first embodiment. Here, n is set to 3, and the case shown is when there are three gas sensors 11 to 13 driven by the microcomputer 10M. n is not limited to 3. The three gas sensors 11 to 13 should be placed as close together as possible in order to unify the surrounding environment. In addition, to prevent two adjacent gas sensors 1 from influencing each other, the gas sensors 11 to 13 should be housed in packages 31 to 33 made of, for example, ceramic.

[0021] Packages 31 to 33 each have storage recesses 311, 321, and 331 for housing gas sensors 11 to 13. The gas sensors 11 to 13 are fixed to the bottom surfaces 312, 322, and 332 of the storage recesses 311, 321, and 331, respectively. Packages 31 to 33 housing the gas sensors 11 to 13 each constitute mounting components 31P to 33P.

[0022] As an example, the control device 10 drives the heaters 107 of the gas sensors 11 to 13 as shown in Figure 5. The control device 10 repeatedly turns the heater 107 of gas sensor 11 on for a time Ton and then off for a time Toff. The thermometer 110 measures the temperature when the heater 107 is on for a time Ton and heating, and the temperature when the heater 107 is off for a time Toff and cooling. Time Ton is, for example, 100 ms, and time Toff is, for example, 100 ms or more.

[0023] The control device 10 repeatedly turns the heater 107 of the gas sensor 12 on and off, starting from the moment the heater 107 of the gas sensor 11 is turned off, and then turning the heater 107 of the gas sensor 12 on for time Ton and then off for time Toff. The thermometer 110 measures the temperature when the heater 107 is on for time Ton and heating, and the temperature when the heater 107 is off for time Toff and cooling.

[0024] The control device 10 turns the heater 107 of the gas sensor 13 on for time Ton and then off for time Toff, starting from the moment the heater 107 of the gas sensor 12 is turned off. The thermometer 110 measures the temperature when the heater 107 is on for time Ton and heating, and the temperature when the heater 107 is off for time Toff and cooling.

[0025] As another example, the control device 10 may drive the heaters 107 of the gas sensors 11 to 13 as shown in Figure 6. The control device 10 repeatedly turns the heater 107 of gas sensor 11 on for a time Ton, and then off for a time Toff that is shorter than Ton. The short time Toff is provided to check for resistance drift in the wiring.

[0026] The control device 10 repeatedly turns the heater 107 of gas sensor 12 on for time Ton and then off for time Toff, starting from the middle of time Ton for the heater 107 of gas sensor 11. The control device 10 also repeatedly turns the heater 107 of gas sensor 13 on for time Ton and then off for time Toff, starting from the middle of time Ton for the heater 107 of gas sensor 12.

[0027] As shown in Figures 5 and 6, the control device 10 can set the on / off timing of the heaters 107 of the gas sensors 1 such that when the heater 107 of one of the n gas sensors 1 is turned off, the heater 107 of another gas sensor 1 among the n gas sensors 1 is turned on. The on / off times Ton and Toff for each gas sensor 1 heater 107, and the voltage value at time Ton, can be set by setting values ​​input to the control device 10.

[0028] In Figures 5 and 6, the control device 10 periodically switches the heater 107 on and off by applying a predetermined voltage to the heater 107 for a time Ton, and by applying no voltage to the heater 107 (applying a voltage of 0) for a time Toff. The control device 10 may also periodically repeat the operation of applying two voltages by making the voltage applied to the heater 107 different in two stages, voltage V1 and voltage V2.

[0029] Furthermore, the control device 10 may periodically repeat the operation of applying three different voltages to the heater 107 by varying the voltage applied to the heater 107 in three stages: voltage V1, voltage V2, and voltage 0. The control device 10 should periodically repeat the operation of applying multiple voltages, including a first voltage and a second voltage, to the heater 107 of the gas sensor 1, so that the heater 107 reaches multiple temperatures. One of the first voltage and the second voltage may be voltage 0.

[0030] An example of an operation in which the thermal conduction gas sensor system drives n gas sensors 1 to calculate gas concentration will be described with reference to the flowchart shown in FIG. 7. FIG. 7 shows an example of turning on / off the heater 107, and shows an example in which the heater 107 of the next gas sensor 1 is turned on after the elapse of the time Ton for turning on the heater 107 of one gas sensor 1.

[0031] In FIG. 7, when the control device 10 starts operation, the control device 10 turns on the heater 107 of the gas sensor 11 in step S11. When the time Ton has elapsed in step S12, the control device 10 acquires the resistance value R when the heater 107 is on in step S13 Ｔ . The control device 10 turns off the heater 107 of the gas sensor 11 in step S14, and reads the resistance value when the heater 107 is off in step S15.

[0032] When the time Ton has elapsed in step S12, the control device 10 turns on the heater 107 of the gas sensor 12 in step S21 in parallel with step S13. When the time Ton has elapsed in step S22, the control device 10 acquires the resistance value R when the heater 107 is on in step S23 Ｔ . The control device 10 turns off the heater 107 of the gas sensor 12 in step S24, and reads the resistance value when the heater 107 is off in step S25.

[0033] When the time Ton has elapsed in step S22, the control device 10 repeats the same operation for the gas sensor 13 and subsequent gas sensors. The control device 10 turns on the gas sensor 1n in step Sn1. When the time Ton has elapsed in step Sn2, the control device 10 acquires the resistance value R when the heater 107 is on in step Sn3 Ｔ . The control device 10 turns off the heater 107 of the gas sensor 1n in step Sn4, and reads the resistance value when the heater 107 is off in step Sn5.

[0034] In step S101, the control device 10 acquires the resistance value R when the gas sensors 11 to 1n are on ＴThe gas concentration is calculated based on the read resistance value when it is off. The control device 10 outputs the calculated value of the gas concentration as data in step S102.

[0035] After the time Ton has elapsed in step Sn2, the control device 10 determines whether an end instruction signal has been input in step S103 in parallel with step Sn3. If the end instruction signal is not input (NO), the control device 10 repeats the operations from step S11 onward. If the end instruction signal is input (YES), the control device 10 executes a normal end process in step S104 and ends the operation.

[0036] As described above, the driving method for the thermal conduction type gas sensor according to the first embodiment is a driving method for driving n gas sensors 1 where n is an integer of 2 or more, and each gas sensor 1 includes a heater 107 and a thermometer 110. In the driving method for the thermal conduction type gas sensor according to the first embodiment, the operation of applying a plurality of voltages including a first voltage and a second voltage to the heater 107 is periodically repeated so that the heater 107 of each gas sensor 1 is set to a plurality of temperatures. As an example, in the driving method for the thermal conduction type gas sensor according to the first embodiment, turning on and off of the heater 107, which is turned off after being turned on, is periodically repeated.

[0037] In the driving method for the thermal conduction type gas sensor according to the first embodiment, the voltage application timing to the heater 107 of each gas sensor 1 is set such that when the second voltage is applied to the heater 107 of any one of the n gas sensors 1, the first voltage is applied to the heater 107 of another gas sensor 1. In the driving method for the thermal conduction type gas sensor according to the first embodiment, when turning on and off of the heater 107 is periodically repeated, the on / off timing is set such that when the heater 107 of any one of the gas sensors 1 is off, the heater 107 of another gas sensor 1 is on.

[0038] As described above, according to the driving method for the thermal conduction type gas sensor according to the first embodiment, the apparent measurement speed for measuring a plurality of temperatures can be increased n times.

[0039] <Second Embodiment> FIGS. 8 and 9 show a mounted component 41P used in a driving method for a heat conduction type gas sensor according to a second embodiment. In the second embodiment, n is set to 4, but n is not limited to 4. FIG. 8 is a top view of a mounted component 41P having four gas sensors 1, and FIG. 9 is a cross-sectional view taken along line A-A of FIG. 8. As shown in FIGS. 8 and 9, the gas sensors 11 to 14 are housed in a package 41 made of ceramic.

[0040] The package 41 has a housing recess 411 that houses the gas sensors 11 to 14. The gas sensors 11 to 14 are fixed to a bottom surface 412 of the housing recess 411 with a gap provided between each other. The package 41 housing the gas sensors 11 to 14 constitutes the mounted component 41P.

[0041] A driving method for a heat conduction type gas sensor according to a second embodiment, which drives the mounted component 41P having four gas sensors 1, is the same as the driving method according to the first embodiment. In the driving method for a heat conduction type gas sensor according to the second embodiment, voltage application timings to the heaters 107 of the respective gas sensors 1 are set such that, at a timing when a second voltage is applied to the heater 107 of any one gas sensor 1 among the n gas sensors 1, a first voltage is applied to the heater 107 of another gas sensor 1.

[0042] According to the driving method for a heat conduction type gas sensor according to the second embodiment, the following effect is achieved in addition to the effect achieved by the driving method according to the first embodiment. Since n gas sensors 1 are housed in a single package 41, the surrounding environment of the n gas sensors 1 can be more uniform. Therefore, the gas concentration can be calculated with higher accuracy.

[0043] <Third Embodiment> FIGS. 10 and 11 show a mounted component 42P used in a driving method for a heat conduction type gas sensor according to a third embodiment. Also in the third embodiment, n is set to 4, but n is not limited to 4. FIG. 10 is a top view of a mounted component 42P having four gas sensors 1, and FIG. 11 is a cross-sectional view taken along line B-B of FIG. 10. As shown in FIGS. 10 and 11, the gas sensors 11 to 14 are housed in a package 42 made of ceramic.

[0044] Package 42 has four storage recesses 421 to 424 for housing gas sensors 11 to 14. Package 42 has isolation walls 429 and 430, which form the four storage recesses 421 to 424. The gas sensors 11 to 14 are fixed to the bottom surfaces 425 to 428 of the storage recesses 421 to 424, respectively. Package 42 housing the gas sensors 11 to 14 constitutes the mounted component 42P.

[0045] The driving method for the heat conduction type gas sensor according to the third embodiment, which drives a mounting component 42P having four gas sensors 1, is the same as the driving method according to the first embodiment. In the driving method for the heat conduction type gas sensor according to the third embodiment, the timing of applying the voltage to the heater 107 of each gas sensor 1 is set such that when a second voltage is applied to the heater 107 of any of the n gas sensors 1, a first voltage is applied to the heater 107 of the other gas sensors 1.

[0046] The driving method for the heat conduction type gas sensor according to the third embodiment provides the following effects in addition to the effects of the driving method according to the second embodiment. The n gas sensors 1 are housed in individual storage recesses 421 to 424 separated by isolation walls 429 and 430. Therefore, they are hardly affected by the heat generated by other gas sensors 1, and the surrounding environment of the n gas sensors 1 can be more uniform. As a result, the gas concentration can be calculated with higher accuracy.

[0047] <Fourth Embodiment> Figure 12 shows the cross-sectional structure of a mounting component 50P used in the driving method of a thermal conduction type gas sensor according to the fourth embodiment. The gas sensor 1T shown in Figure 12 is housed in a package 50 made of ceramic. The package 50 has a housing recess 501 for housing the gas sensor 1T. The gas sensor 1T is fixed to the bottom surface 502 of the housing recess 501. The package 50 housing the gas sensor 1T constitutes the mounting component 50P.

[0048] The gas sensor 1T is configured as follows. As shown in Figure 12, an insulating film 121 is formed on the silicon substrate 101. In detail, the insulating film 121 is formed in three layers, similar to the insulating films 102, 103, and 104 shown in Figure 2. Here, n is set to 3, but n is not limited to 3. Sensor regions Rs1 to Rs3, which function as a heat conduction type gas sensor, are provided in three regions located at different positions within the insulating film 121, each region having a heater 107 and a thermometer 110. Sensor regions of any number will be referred to as sensor region Rs.

[0049] In sensor region Rs1, the heater 107 and thermometer 110 are heater 107a and thermometer 110a. In sensor region Rs2, the heater 107 and thermometer 110 are heater 107b and thermometer 110b. In sensor region Rs3, the heater 107 and thermometer 110 are heater 107c and thermometer 110c. Heaters 107a to 107c have the same configuration as heater 107 shown in Figure 2, and thermometers 110a to 110c have the same configuration as thermometer 110 shown in Figure 2.

[0050] The driving method for a heat-conducting gas sensor according to the fourth embodiment, which drives a mounting component 50P having a gas sensor 1T including three sensor regions Rs1 to Rs3, is basically the same as the driving method according to the first embodiment and is as follows.

[0051] The control device 10 periodically repeats the operation of applying a plurality of voltages, including a first voltage and a second voltage, to the heaters 107 provided in each of the n sensor regions Rs so that the heaters 107 in each sensor region Rs reach a plurality of temperatures. The control device 10 sets the timing of voltage application to the heaters 107 in each sensor region Rs such that when the second voltage is applied to the heater 107 in any of the n sensor regions Rs, the first voltage is applied to the heater 107 in the other sensor regions Rs.

[0052] According to the driving method for the thermal conduction gas sensor of the fourth embodiment, the apparent measurement speed for measuring multiple temperatures can be increased by n times. According to the driving method for the thermal conduction gas sensor of the fourth embodiment, a gas sensor 1T that can increase the apparent measurement speed for measuring multiple temperatures by n times can be configured on a single chip.

[0053] Figure 13 shows a modified version of the mounting component 50P shown in Figure 12, which is a mounting component 50P'. The mounting component 50P' houses a gas sensor 1T' within a package 50. Grooves 122 and 123, from which the insulating film 121 has been removed, are formed between two adjacent sensor regions Rs, in this case between sensor region Rs1 and sensor region Rs2, and between sensor region Rs2 and sensor region Rs3. Groove 122 separates sensor region Rs1 and sensor region Rs2, and groove 123 separates sensor region Rs2 and sensor region Rs3.

[0054] Since the gas sensor 1T' has grooves 122 and 123 that separate two adjacent sensor regions Rs, it can suppress the conduction of heat generated in the adjacent sensor regions Rs. Therefore, the gas sensor 1T' can be driven with almost no influence from the heat generated in the adjacent sensor regions Rs.

[0055] In the heat conduction type gas sensor according to the fourth embodiment, the control device 10 may repeatedly turn on and off the heaters 107 so that the heaters 107 provided in each of the n sensor regions Rs reach multiple temperatures. In this case, the control device 10 sets the on / off timing of the heaters 107 in each sensor region Rs such that when the heater 107 in one of the n sensor regions Rs is turned off, the heater 107 in another sensor region Rs is turned on.

[0056] Although the present disclosure has been described in detail above, it will be clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. One or more elements of each embodiment can be combined with one or more elements of other embodiments. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Accordingly, the descriptions in the present disclosure are for illustrative purposes only and are not intended to be restrictive in any way.

[0057] (Note) The technical concepts that can be grasped from this disclosure are described below. Not with the intention of limiting, but for the purpose of aiding understanding, the components described in the notes are denoted by the reference numerals of the corresponding components in the embodiments. The reference numerals are shown as examples for the purpose of aiding understanding, and the components described in each note should not be limited to those indicated by the reference numerals.

[0058] (Note 1) The method for driving the heat conduction gas sensor is a method in which each heat conduction gas sensor 1 drives n heat conduction gas sensors 1, each having a heater 107 and a thermometer 110, with n being an integer of 2 or more. The method for driving the heat conduction gas sensor periodically repeats the operation of applying a plurality of voltages, including a first voltage and a second voltage, to the heater 107 of each heat conduction gas sensor 1, so that the heater 107 of each heat conduction gas sensor 1 reaches a plurality of temperatures. The timing of applying voltage to the heater 107 of each heat conduction gas sensor 1 is set such that when the second voltage is applied to the heater 107 of any of the n heat conduction gas sensors 1, the first voltage is applied to the heater 107 of another heat conduction gas sensor 1 among the n heat conduction gas sensors 1.

[0059] According to the driving method for the heat conduction type gas sensor described in Appendix 1, the apparent measurement speed for measuring multiple temperatures can be increased by n times.

[0060] (Note 2) In the method for driving a thermal conduction gas sensor described in Note 1, the n thermal conduction gas sensors 1 are mounted components 41P or 42P housed in a package 41 or 42. According to the method for driving a thermal conduction gas sensor described in Note 2, in addition to the effects of the method for driving a thermal conduction gas sensor described in Note 1, the surrounding environment of the n thermal conduction gas sensors 1 can be made more uniform, so the gas concentration can be calculated with higher accuracy.

[0061] (Note 3) In the method for driving a thermal conduction gas sensor described in Note 2, the package 42 has isolation walls 429 and 430 that isolate the n thermal conduction gas sensors 1 housed within the package 42 from each other. According to the method for driving a thermal conduction gas sensor described in Note 3, the surrounding environment of the n thermal conduction gas sensors 1 can be unified even more than in the method for driving a thermal conduction gas sensor described in Note 2, and the gas concentration can be calculated with higher accuracy.

[0062] (Note 4) When n is an integer of 2 or more, sensor regions Rs1 to Rs3 are provided in each of n regions within the insulating film 121 that are at different positions from each other, and each region has a heater 107 and a thermometer 110, functioning as a heat conduction type gas sensor. Each of the heaters 107 provided in sensor regions Rs1 to Rs3 is a heater 107a to 107c, and each of the thermometers 110 is a thermometer 110a to 110c.

[0063] The driving method for the heat conduction gas sensor involves periodically repeating the operation of applying multiple voltages, including a first voltage and a second voltage, to the heaters 107, which are provided in each of the n sensor regions Rs1 to Rs3, so that the heaters 107 reach multiple temperatures. The driving method for the heat conduction gas sensor sets the timing of voltage application to the heaters 107 in each sensor region such that when the second voltage is applied to the heater 107 in any of the n sensor regions Rs1 to Rs3, the first voltage is applied to the heater 107 in another of the n sensor regions Rs1 to Rs3.

[0064] According to the driving method for the thermal conduction gas sensor described in Appendix 4, a thermal conduction gas sensor 1T that can increase the apparent measurement speed for measuring multiple temperatures by n times can be configured on a single chip.

[0065] (Note 5) In the method for driving a thermal conduction gas sensor described in Note 4, grooves 122 and 123 are formed between two adjacent sensor regions among the n sensor regions Rs1 to Rs3, with the insulating film 121 removed, to demarcate the two sensor regions. According to the method for driving a thermal conduction gas sensor described in Note 5, the conduction of heat generated in adjacent sensor regions Rs can be suppressed, so the thermal conduction gas sensor 1T' can be driven with almost no influence from the heat generated in adjacent sensor regions Rs.

[0066] 1, 11-1n, 1T, 1T' Thermal conduction gas sensor 10 Control device 10M Microcomputer 21 Temperature sensor IC 22 Boost circuit 23 Amplifier 24 Resistance measurement circuit 31-33, 41, 42, 50 Package 31P-33P, 41P, 42P, 50P, 50P' Mounted components 101 Silicon substrate 102, 103, 104, 121 Insulating film 105, 108 Electrode 106, 109 Titanium oxide film 107, 107a-107c Heater 110, 110a-110c Thermometer 122, 123 Groove 311, 321, 331, 411, 421-424, 501 Storage recess 312, 322, 332, 412, 425-428, 502 Bottom surface Rs, Rs1-Rs3 Sensor area

Claims

1. A driving method for driving a thermal conduction gas sensor, wherein n is an integer of 2 or more, and each thermal conduction gas sensor has a heater and a thermometer, wherein the operation of periodically applying a plurality of voltages, including a first voltage and a second voltage, to the heater of each thermal conduction gas sensor so that the heater of each thermal conduction gas sensor reaches a plurality of temperatures, is repeated, and the timing of applying voltage to the heater of each thermal conduction gas sensor is set such that when the second voltage is applied to the heater of any of the n thermal conduction gas sensors, the first voltage is applied to the heater of another thermal conduction gas sensor among the n thermal conduction gas sensors.

2. The method for driving a thermal conductive gas sensor according to claim 1, wherein the n thermal conductive gas sensors are mounted components housed in a package.

3. The method for driving a heat conduction gas sensor according to claim 2, wherein the package has isolation walls that separate the n heat conduction gas sensors housed in the package from each other.

4. A method for driving a heat conduction gas sensor, wherein n is an integer of 2 or more, and each of n regions located at different positions within an insulating film is provided with a sensor region that functions as a heat conduction gas sensor having a heater and a thermometer; the operation of periodically applying a plurality of voltages, including a first voltage and a second voltage, to the heaters in each of the n sensor regions so that the heaters in each sensor region reach a plurality of temperatures; and the timing of applying voltage to the heaters in each of the n sensor regions is set such that when the second voltage is applied to the heater in one of the n sensor regions, the first voltage is applied to the heater in another of the n sensor regions.

5. A method for driving a thermal conduction gas sensor according to claim 4, wherein a groove is formed between two adjacent sensor regions among the n sensor regions, the insulating film being removed, to demarcate the two sensor regions.

Images