Concentration measurement method, flow rate measurement method, sensor module for making measurements with same, control device, control method, and control program

Abstract

[Problem] To provide: a concentration measurement method and a flow rate measurement method that make it possible to accurately measure a gas concentration and flow rate even after a long period of use, thus making it possible to improve the durability of a sensor; a sensor module for making measurements with these methods; a control device; a control method; and a control program. [Solution] The present invention comprises: a thermal-conduction-type sensor that has a heat-generating resistor which generates heat upon energization; and a control device that controls the application of a voltage or current to the thermal-conduction-type sensor, and that is configured to acquire a resistance value of the heat-generating resistor from the thermal-conduction-type sensor. The control device acquires a first detection value of the heat-generating resistor after a prescribed time has elapsed after supplying a first electric power to the heat-generating resistor; acquires a second detection value of the heat-generating resistor after a prescribed time has elapsed after supplying a second electric power, which is greater than the first electric power, to the heat-generating resistor; and, on the basis of the first detection value and the second detection value, calculates the concentration of a target gas subject to measurement contained in a gas subject to measurement and / or the flow rate of the gas subject to measurement.

Description

Methods for measuring concentration and flow rate, as well as sensor modules, control devices, control methods, and control programs for these measurements.

[0001] The present invention relates to a method for measuring concentration and a method for measuring flow rate using a thermal conduction sensor having a heat-generating resistor that generates heat when an electric current is applied, as well as a sensor module, control device, control method, and control program for these measurements.

[0002] Conventionally, various devices have been known for measuring the gas concentration and flow rate of a gas under test. One such device is a thermal conduction gas sensor. In a thermal conduction gas sensor, heat generated by a heat-generating resistor is conducted to the gas under test, and the gas concentration and flow rate of the gas under test are measured based on the heat lost from the heat-generating resistor.

[0003] For example, Patent Document 1 discloses a combustible gas detection device equipped with a heat conduction type gas detection unit. Patent Document 2 also discloses a heat conduction type gas concentration measuring device with a simpler structure.

[0004] Furthermore, Patent Document 3 discloses a gas sensor that uses a thermal conduction type sensor having a heat-generating resistor that generates heat when an electric current is applied.

[0005] Japanese Patent Publication No. 2005-156364, Japanese Patent Publication No. 7503226, Japanese Patent Publication No. 2005-043208

[0006] In thermal conduction sensors, the heat generated by the heat-generating resistor changes the sensor's temperature, and consequently, the sensor's resistance also changes. When such thermal conduction sensors are used continuously, resistance drift occurs, causing the sensor's resistance to change with temperature.

[0007] Figure 16 is a graph showing the change in the resistance value of a heat-generating resistor in a thermal conduction sensor over time, with the surface temperature of the resistor set to 400°C. As shown in Figure 16, the resistance value of the heat-generating resistor drifts and decreases with continued use. Such changes in resistance value lead to errors in the detected gas concentration, flow rate, and temperature, making accurate measurement impossible and rendering the device unusable as a gas concentration measuring device.

[0008] Furthermore, Figure 16 shows the results when the time from supplying power to the heating resistor to measuring the resistance value was 20 seconds, 40 seconds, 70 seconds, 190 seconds, and 310 seconds, respectively. It can be seen that even when the time is changed, the results are affected by the drift in the resistance value of the heating resistor.

[0009] Furthermore, thermal conduction sensors are also affected by ambient temperature. Figure 17 is a graph showing the relationship between the supplied oxygen concentration and the calculated oxygen concentration when oxygen concentration is measured using a thermal conduction sensor.

[0010] The graph in Figure 17 shows that the calculated oxygen concentration is based on a calibration curve that uses the detected value obtained by a thermal conduction sensor at an ambient temperature of 25°C as a reference. As shown in Figure 17, a large error occurs in the calculated oxygen concentration as the ambient temperature changes.

[0011] Traditionally, such changes in ambient temperature were addressed by adding temperature compensation sensors. However, adding such temperature compensation sensors requires additional space. Furthermore, adding temperature compensation sensors leads to increased manufacturing costs. Moreover, power is required to operate the temperature compensation sensors, resulting in increased power consumption.

[0012] On the other hand, the gas sensor disclosed in Patent Document 3 performs humidity compensation using two outputs L and H obtained by applying current to the heater of a heat conduction sensor, without using a temperature compensation sensor. However, this is solely for humidity compensation and is not used to compensate for changes in ambient temperature as described above.

[0013] In view of the current situation, the present invention aims to provide a method for measuring gas concentration and flow rate, as well as a sensor module, control device, control method, and control program for these measurements, that can accurately measure gas concentration and flow rate even when the resistance value of the heating resistor drifts after long-term use or when the ambient temperature changes, that is, to improve the durability of the sensor and to accurately measure without using a temperature-compensated sensor.

[0014] The present invention was invented to solve the problems of the prior art described above, and the present invention includes the following configuration.

[0015] [1] A concentration measurement method for measuring the concentration of a target gas contained in a gas to be measured using a thermal conduction sensor having a heat-generating resistor that generates heat when an electric current is applied, the method comprising: firstly, after supplying a first power, the second detected value of the heat-generating resistor after a predetermined time has elapsed; and secondly, after supplying a second power greater than the first power, the second detected value is corrected using two correspondences, one between the first detected value and the ambient temperature and the other between the second detected value and the ambient temperature, which have been acquired in advance, or using the correspondence between the first detected value and the second detected value, which have been acquired in advance; and calculation of the concentration of the target gas contained in the gas to be measured based on a calibration curve between the second detected value and the concentration of the target gas created by acquiring measurement points that show the relationship between the second detected value and the concentration of the target gas at one or more ambient temperatures acquired in advance, within a desired concentration range for which measurement is to be performed, and / or by acquiring three or more of the measurement points, and the corrected second detected value.

[0016] [2] The concentration measurement method according to [1], wherein the correspondence is a calibration curve.

[0017] [3] A concentration measurement method according to [1] or [2], which calculates the concentration of the target gas contained in the target gas based on a calibration curve of the second detection value for each ambient temperature obtained in advance and the concentration of the target gas, and the corrected second detection value.

[0018] [4] The concentration measurement method according to any one of [1] to [3], wherein the second power is the power at which the surface temperature of the heating resistor becomes a predetermined temperature.

[0019] [5] The concentration measurement method according to [4], wherein the predetermined temperature is 50°C to 800°C.

[0020] [6] The heat conduction type sensor has a heating resistor that generates heat by energization and a stage that supports the heating resistor, the heating resistor overlaps the stage in a plan view, and the area S of the stage in a plan view is 3.6×10 ７ μm ２ or less, and when the total volume of the heating resistor and the stage is V, S / V is 0.0010μm －１ or more and 10μm －１ or less. The concentration measurement method according to any one of [1] to [5].

[0021] [7] A flow rate measurement method for measuring the flow rate of a gas to be measured using a heat conduction type sensor having a heating resistor that generates heat by energization. After supplying a first power, the first detection value of the heating resistor after a predetermined time has elapsed, and after supplying a second power greater than the first power, based on the second detection value of the heating resistor after a predetermined time has elapsed, using two correspondence relationships between the first detection value and the ambient temperature acquired in advance and between the second detection value and the ambient temperature acquired in advance, or using the correspondence relationship between the first detection value and the second detection value acquired in advance, correct the second detection value, and for the measurement points showing the relationship between the second detection value at one or more ambient temperatures acquired in advance and the flow rate of the gas to be measured, obtain the measurement points in the desired flow rate range to be measured, and / or obtain three or more of the measurement points, and based on the calibration curve between the second detection value and the flow rate of the gas to be measured created thereby and the corrected second detection value, calculate the flow rate of the gas to be measured. Flow rate measurement method.

[0022] [8] The flow rate measurement method according to [7], wherein the correspondence relationship is a calibration curve.

[0023] [9] The flow rate measurement method according to [7] or [8], which calculates the flow rate of the gas to be measured based on the calibration curve of the second detection value for each environmental temperature acquired in advance and the flow rate of the gas to be measured, and the corrected second detection value.__

[0024]

[10] The flow rate measurement method according to any one of [7] to [9], wherein the second power is the power at which the surface temperature of the heating resistor becomes a predetermined temperature.__

[0025]

[11] The flow rate measurement method according to

[10] , wherein the predetermined temperature is 50°C to 800°C.__

[0026]

[12] The heat conduction type sensor has a heating resistor that generates heat by being energized and a stage that supports the heating resistor, the heating resistor overlaps the stage in a plan view, the area S of the stage in a plan view is 3.6×10__ ７ μm__ ２ or less, when the total volume of the heating resistor and the stage is V, S / V is 0.0010 μm__ －１ or more and 10 μm__ －１ or less. The flow rate measurement method according to any one of [7] to

[11] .__

[0027]

[13] A sensor module for measuring the concentration of at least one of the target gases to be measured contained in the gas to be measured, or the flow rate of the gas to be measured, comprising: a thermal conduction sensor having a heat-generating resistor that generates heat when energized; and a control device configured to control the application of voltage or current to the thermal conduction sensor and to acquire the resistance value of the heat-generating resistor from the thermal conduction sensor, wherein the control device acquires a first detected value of the heat-generating resistor after a predetermined time has elapsed since supplying a first power to the heat-generating resistor, acquires a second detected value of the heat-generating resistor after a predetermined time has elapsed since supplying a second power greater than the first power to the heat-generating resistor, corrects the second detected value using two correspondences: the correspondence between the first detected value and the ambient temperature acquired in advance and the correspondence between the second detected value and the ambient temperature acquired in advance, or using the correspondence between the first detected value and the second detected value acquired in advance. A sensor module that calculates the concentration of the gas to be measured based on a calibration curve between the second detected value and the concentration of the gas to be measured, created by acquiring measurement points in a desired concentration range for measurement, and / or by acquiring three or more of the measurement points, and the corrected second detected value, and / or by acquiring measurement points in a desired flow rate range for measurement, and / or by acquiring three or more of the measurement points, and the corrected second detected value, and / or by calculating the flow rate of the gas to be measured, and

[0028]

[14] The sensor module described in

[13] wherein the correspondence is a calibration curve.

[0029]

[15] A control device for measuring at least one of the concentration of at least one target gas to be measured and the flow rate of the gas to be measured, using a thermal conduction sensor having a heat-generating resistor that generates heat when an electric current is applied, comprising: a power supply unit that supplies predetermined power to the heat-generating resistor; a resistor measuring unit that measures at least one of the resistance value of the heat-generating resistor, the voltage value across the ends of the heat-generating resistor, and the current value flowing through the heat-generating resistor; a time control unit that controls the time for the resistor measuring unit to detect the resistance value; and a calculation unit that calculates at least one of the concentration of at least one target gas to be measured and the flow rate of the gas to be measured, based on the resistance value detected by the resistor measuring unit, wherein the calculation unit supplies first power to the heat-generating resistor by the power supply unit, measures time by the time control unit, and obtains a first detected value of the heat-generating resistor detected by the resistor measuring unit after a predetermined time has elapsed. The power supply unit supplies a second power greater than the first power to the heating resistor, the time control unit measures time, and after a predetermined time has elapsed, the resistor measurement unit obtains the second detected value of the heating resistor. The second detected value is corrected using two correspondences: the correspondence between the previously obtained first detected value and the ambient temperature, and the correspondence between the previously obtained second detected value and the ambient temperature, or using the correspondence between the previously obtained first detected value and the second detected value.A control device that calculates the concentration of the gas to be measured based on a calibration curve between the second detected value and the concentration of the gas to be measured, created by acquiring measurement points in a desired concentration range for measurement, and / or by acquiring three or more of the measurement points, and the corrected second detected value, and / or by acquiring measurement points in a desired flow rate range for measurement, and / or by acquiring three or more of the measurement points, and the corrected second detected value, and the flow rate of the gas to be measured, and / or by acquiring measurement points in a desired flow rate range for measurement, and / or by acquiring three or more of the measurement points, and the corrected second detected value.

[0030]

[16] A control method for controlling a control device that measures at least one of the concentration of at least one target gas to be measured or the flow rate of a gas to be measured, using a thermal conduction sensor having a heat-generating resistor that generates heat when an electric current is applied, the method comprising: a step of supplying a first power to the heat-generating resistor in the thermal conduction sensor and then acquiring a first detected value of the heat-generating resistor after a predetermined time has elapsed; a step of supplying a second power greater than the first power to the heat-generating resistor in the thermal conduction sensor and then acquiring a second detected value of the heat-generating resistor after a predetermined time has elapsed; and a step of correcting the second detected value using two correspondence relationships, one between the previously acquired first detected value and the ambient temperature and the other between the previously acquired second detected value and the ambient temperature, or using the correspondence relationship between the previously acquired first detected value and the second detected value. A control method comprising the steps of: acquiring measurement points in a desired concentration range for which measurement is to be performed, with respect to a relationship between a second detected value and the concentration of the gas to be measured, with respect to measurement points that show the relationship between a second detected value and the concentration of the gas to be measured, with respect to measurement points that show the relationship between a second detected value and the concentration of the gas to be measured, with respect to measurement points that show the relationship between a second detected value and the flow rate respect to a desired flow rate range for which measurement is to be performed, with respect to measurement points that show respect to a relationship between a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a relationship between a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a relationship between a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a desired flow rate range for which measurement is to be performed, with respect to measurement points that show respect to a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a relationship between a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a desired flow rate for which measurement is to be performed, with respect to measurement points that show respect to a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a second detected value and the concentration of the gas to be measured, with respect to

[0031]

[17] A control program for measuring at least one of the concentration of at least one target gas contained in a gas to be measured, or the flow rate of a gas to be measured, using a thermal conduction sensor having a heat-generating resistor that generates heat when an electric current is applied, comprising: a step of supplying a first power to the heat-generating resistor and then acquiring a first detected value of the heat-generating resistor after a predetermined time has elapsed; a step of supplying a second power greater than the first power to the heat-generating resistor and then acquiring a second detected value of the heat-generating resistor after a predetermined time has elapsed; and a step of correcting the second detected value using two correspondence relationships, namely the correspondence relationship between the first detected value and the ambient temperature acquired in advance and the correspondence relationship between the second detected value and the ambient temperature acquired in advance, or using the correspondence relationship between the first detected value and the second detected value acquired in advance. A control program that causes the program to execute the following steps: acquiring measurement points in a desired concentration range for which measurement is to be performed, for measurement points that show the relationship between a second detected value and the concentration of the gas to be measured, which have been acquired in advance at one or more ambient temperatures; and / or calculating the concentration of the gas to be measured based on a calibration curve between the second detected value and the concentration of the gas to be measured, created by acquiring three or more of the measurement points, and the corrected second detected value; and / or calculating the flow rate of the gas to be measured based on a calibration curve between the second detected value and the flow rate of the gas to be measured, created by acquiring three or more of the measurement points that show the relationship between a second detected value and the flow rate of the gas to be measured, which have been acquired in advance at one or more ambient temperatures, and the corrected second detected value.

[0032] According to the present invention, by measuring the concentration of the gas to be measured and the flow rate of the gas to be measured based on a corrected resistance value calculated from a first detected value, which is the resistance value of the heating resistor measured after a predetermined time has elapsed following the supply of a first power to the heating resistor, and a second detected value, which is the resistance value of the heating resistor measured after a predetermined time has elapsed following the supply of a second power greater than the first power to the heating resistor, the effects of resistance value drift and the effects of changes in ambient temperature can be corrected, and accurate measurements of gas concentration and gas flow rate can be performed over a long period of time.

[0033] Figure 1 is a schematic diagram showing one embodiment of the sensor module of the present invention. Figure 2 is a schematic perspective view showing the structure of the thermal conduction sensor in this embodiment. Figure 3 is a plan view showing the position and shape of the heating resistor in the thermal conduction sensor shown in Figure 2. Figure 4 is a cross-sectional view of the thermal conduction sensor shown in Figure 2 along the line IV-IV. Figure 5 is a perspective view showing a modified example of the structure of the thermal conduction sensor. Figure 6 is a plan view showing the position and shape of the heating resistor in the thermal conduction sensor shown in Figure 5. Figure 7 is a cross-sectional view of the thermal conduction sensor shown in Figure 5 along the line VII-VII. Figure 8 is a graph showing the corrected detected value when measuring oxygen gas of known concentration using the sensor module shown in Figure 1. Figure 9 is a graph showing the change in the corrected detected value over time. Figure 10 is a graph showing the detected value (resistance value) when measuring a nitrogen / carbon dioxide mixed gas using the sensor module shown in Figure 1. Figure 11 is a graph showing the detected value (voltage value) when measuring a nitrogen / carbon dioxide mixed gas using the sensor module shown in Figure 1. Figure 12 is a graph showing the detected value (resistance value) when measuring a nitrogen-argon mixed gas using the sensor module shown in Figure 1. Figure 13 is a graph showing the relationship between the supplied oxygen concentration and the calculated oxygen concentration when measuring the oxygen concentration using the sensor module shown in Figure 1. Figure 14 is a graph showing the correspondence between the supplied oxygen concentration and the corrected detected value at an ambient temperature of 25°C. Figure 15(a) is a graph showing the relationship between the supplied oxygen concentration and the calculated oxygen concentration when measuring the oxygen concentration using the sensor module shown in Figure 1, using the correspondence shown in Figure 14, and Figure 15(b) shows the relationship between the supplied oxygen concentration and the concentration error. Figure 16 is a graph showing the change in the resistance value of the heating resistor of the thermal conduction sensor over time when the surface temperature of the heating resistor is set to 400°C. Figure 17 is a graph showing the relationship between the supplied oxygen concentration and the calculated oxygen concentration when measuring the oxygen concentration using a thermal conduction sensor.

[0034] Hereinafter, embodiments (examples) of the present invention will be described in more detail with reference to the drawings. Figure 1 is a schematic diagram showing one embodiment of the sensor module of the present invention. As shown in Figure 1, the sensor module 1 of this embodiment comprises a thermal conduction sensor 10 and a control device 50.

[0035] The thermal conduction sensor 10 has a heat-generating resistor 31 that generates heat when an electric current is applied. More specifically, as shown in Figures 2 to 4, the thermal conduction sensor 10 in this embodiment comprises a stage 21 and one or more bridges 22 extending from the periphery of the stage 21, forming a bridge structure 20. In the thermal conduction sensor 10 shown in Figure 2, the bridge structure 20 has a stage 21 which is a rectangular plate-like body in plan view, and four bridges 22 extending from the periphery of the stage 21. The bridges 22 extend from the four corners of the stage 21. The thermal conduction sensor 10 also has a peripheral portion 24 that is connected to the bridges 22 and surrounds the stage 21. Note that the shape of the stage 21 in plan view is not limited to a rectangle.

[0036] As shown in Figure 4, the stage 21 has a multilayer structure. More specifically, the stage 21 has a four-layer structure consisting of a first insulating layer 121, a second insulating layer 122 placed on the first insulating layer 121, a third insulating layer 123 placed on the second insulating layer 122, and a fourth insulating layer 124 placed on the third insulating layer 123. However, the layer structure of the stage 21 is not limited to this, and for example, the stage 21 may have a single-layer structure, a two-layer structure, or a three-layer structure. Note that in the thermal conduction sensor 10 shown in Figure 3, the fourth insulating layer 124 and the second contact layer 34, which will be described later, are omitted from the illustration in order to clearly show the position and shape of the heat-generating resistor 31, which will be described later.

[0037] The heat-generating resistor 31 is supported by the stage 21 and overlaps with the stage 21 in a plan view. More specifically, in the embodiments shown in Figures 2 to 4, the stage 21 contains the heat-generating resistor 31 inside its thickness. In this embodiment, the heat-generating resistor 31 is placed on the third insulating layer 123, and the fourth insulating layer 124 is placed above and to the side of it. In this way, the heat-generating resistor 31 is surrounded by the third insulating layer 123 and the fourth insulating layer 124, preventing contact with the surrounding gas, thereby improving the durability of the heat-generating resistor 31.

[0038] The heat-generating resistor 31 preferably consists of a series of linear members. In this specification, "a series of linear members" means a single linear member, or a plurality of linear members that share at least two ends.

[0039] The series of wires arranged in the stage 21 form a heat-generating resistor 31 within the stage 21. The series of wires also extends to two bridges 22, 22 and the peripheral portion 24, forming two wires 312, 312. In other words, the series of wires consists of a heat-generating resistor 31 arranged in the stage 21 and wires 312 extending to the bridges 22 and the peripheral portion 24. To enable the formation of these two wires 312, 312, it is preferable that two or more bridges 22 extend from the peripheral edge of the stage 21. Furthermore, from the viewpoint of more stably supporting the stage 21, it is preferable that three or more, and more preferably four or more, bridges 22 extend from the peripheral edge of the stage 21.

[0040] The heating resistor 31 is connected to two wire bonding pads 32, 32 (hereinafter also simply referred to as "pads 32") located on the peripheral edge 24 via two wires 312, 312.

[0041] The heating resistor 31 shown in Figure 3 consists of a single linear structure. This linear structure extends within the stage 21, repeatedly meandering in one direction and the opposite direction without intersecting. This shape of the linear structure allows for an increase in the resistance value of the heating resistor 31. As a result, gas concentration measurement becomes possible with lower power consumption.

[0042] An example of an embodiment in which the heat-generating resistor 31 consists of a plurality of linear bodies having at least two common ends is an embodiment (not shown) in which the plurality of linear bodies are arranged in the stage 21 so as not to intersect with each other, and the portions of the plurality of linear bodies arranged in the bridge 22 are common (overlapping with each other).

[0043] From the viewpoint of sufficiently increasing the physical strength of the heating resistor 31 and from the viewpoint of sufficiently increasing the resistance value of the heating resistor 31 to reduce the power consumption of the heat conduction type sensor 10, the thickness of the heating resistor 31 is preferably 0.01 μm or more and 100 μm or less, more preferably 0.02 μm or more and 75 μm or less, and still more preferably 0.05 μm or more and 50 μm or less.

[0044] The thicknesses of the heating resistor 31 and the first adhesion layer 33 and the second adhesion layer 34 described later can be measured by a stylus type profilometer, an electron microscope or an optical three-dimensional measuring instrument.

[0045] Further, the heat absorption amount of the gas to be measured depends on the flow rate of the gas to be measured. From this, based on the resistance value of the heating resistor 31, the flow rate of the gas to be measured can be measured. Furthermore, since the thermal conductivity of the gas to be measured changes depending on the composition of the gas, the temperature of the heating resistor in the steady state changes according to the composition of the mixed gas. From this, based on the resistance value of the heating resistor 31, the concentration of the gas to be measured in the gas to be measured can be measured.

[0046] As a result of the studies by the present inventors, by setting the heat capacity of the heating resistor 31 and its surroundings to a predetermined value or less, the amount of temperature change of the heating resistor 31 corresponding to changes in the flow rate of the gas to be measured and the concentration of the gas to be detected can be sufficiently increased. Therefore, it has been found that the measurement accuracy and measurement sensitivity of the flow rate of the gas to be measured and the concentration of the gas to be detected in the gas to be measured can be improved. Specifically, the total heat capacity of the heating resistor 31 and the stage 21 is preferably 3.2×10 －２ J / K or less, more preferably 2.2×10 －２ J / K or less, and still more preferably 1.5×10 －２ J / K or less.

[0047] Also, from the viewpoint of reducing power consumption, the total heat capacity of the heating resistor 31 and the stage 21 is preferably 1.0×10 －１０ J / K or more, more preferably 1.0×10 －９ J / K or more, and still more preferably 2.0×10 －９ J / K or more.

[0048] As previously explained, the thermal conduction sensor 10 shown in Figures 2 to 4 has a bridge structure 20 consisting of a stage 21 containing a heat-generating resistor 31 and a bridge 22. By employing a thermal conduction sensor 10 having such a structure as the thermal conduction sensor 10 of the present invention, the heat capacity of the portion overlapping with the heat-generating resistor 31 in a plan view can be easily controlled within the above range.

[0049] From the viewpoint of controlling the heat capacity of the portion overlapping with the heat-generating resistor 31 in a plan view within the above range and ensuring sufficient mechanical strength, the area S of the stage 21 in a plan view is 3.6 × 10 ７ μm ２ Preferably, it is 3.0 × 10 ７ μm ２ It is more preferable that the following conditions apply: 2.5 × 10 ７ μm ２ The following is even more preferable:

[0050] Furthermore, from the viewpoint of improving the efficiency of heat transfer with the gas being measured, S is set to 100 μm. ２ Preferably, the size is 200 μm or larger. ２ It is more preferable that the amount be greater than or equal to 400 μm. ２ It is even more preferable that the above conditions are met.

[0051] From a similar viewpoint, if the stage 21 is rectangular, provided that S is within the range described above, the length of one side of the stage 21 is preferably 10 μm or more and 3000 μm or less, more preferably 12.5 μm or more and 2500 μm or less, and even more preferably 20 μm or more and 2000 μm or less.

[0052] From the viewpoint of ensuring sufficient heat absorption by the gas being measured and improving the measurement accuracy and sensitivity of the flow rate of the gas being measured and the concentration of the gas to be detected, when the total volume of the heat-generating resistor 31 and the stage 21 is V, S / V is 0.0010 μm －１ Preferably, the size is 0.00125 μm or larger. －１ It is more preferable that the amount be greater than or equal to 0.0016 μm. －１ It is even more preferable that the above conditions are met.

[0053] Furthermore, from the perspective of reducing power consumption, the S / V ratio is 10 μm. －１ Preferably, the following is true: 7.0 μm －１ The following is more preferable: 5.0 μm －１ The following is even more preferable:

[0054] From the viewpoint of further improving the measurement accuracy and sensitivity of the flow rate of the gas to be measured and the concentration of the target gas to be detected, it is preferable that the heat-generating resistor 31 has a high temperature dependence of its resistance value. Specifically, the temperature coefficient of resistance αt of the heat-generating resistor 31 at 25°C is preferably 100 ppm / °C or more, more preferably 500 ppm / °C or more, and even more preferably 1000 ppm / °C or more.

[0055] Materials having a temperature coefficient of resistance αt of 100 ppm / °C or higher at 25°C include platinum, tungsten, copper, gold, silver, molybdenum, aluminum, and tantalum, as well as alloys thereof. Examples of platinum-containing alloys include Pt-Nb, Pt-Rh, and Pt-W. Another example is a cermet made of platinum group elements (platinum, palladium, rhodium, ruthenium, iridium, and osmium) and / or alloys containing these elements and metal oxides. Therefore, it is preferable that the heating resistor 31 contains one or more materials selected from this group. In particular, from the viewpoint of stability in high-temperature environments, it is especially preferable that the heating resistor 31 contains platinum or a platinum-containing alloy.

[0056] From the viewpoint of improving the durability of the heat conduction sensor 10 by increasing the adhesion between the heat-generating resistor 31 and the third insulating layer 123 and the fourth insulating layer 124, it is preferable that the first adhesion layer 33 and the second adhesion layer 34 are arranged at positions that are in contact with the lower surface and upper surface of the heat-generating resistor 31, respectively.

[0057] When the first contact layer 33 and the second contact layer 34 are positioned in contact with the lower and upper surfaces of the heat-generating resistor 31, it is preferable that the first contact layer 33 and the second contact layer 34 are also positioned in contact with the lower and upper surfaces of the wiring 312 and the pad 32.

[0058] From the viewpoint of sufficiently improving the adhesion between the heat-generating resistor 31 and the third insulating layer 123 and the fourth insulating layer 124, the thickness of the first adhesion layer 33 and the second adhesion layer 34 are, independently of each other, preferably 1 nm to 200 nm, more preferably 2 nm to 150 nm, and even more preferably 10 nm to 100 nm.

[0059] As shown in Figures 2 and 4, a portion of the fourth insulating layer 124 placed on the pad 32 has been removed. As a result, the second adhesion layer 34 (or a portion of the pad 32 in embodiments where the second adhesion layer does not exist) is exposed to the outside.

[0060] As described above, the heat conduction sensor 10 has a peripheral portion 24 that surrounds the stage 21. Preferably, the peripheral portion 24 is spaced apart from the stage 21 and the two are connected via a bridge 22.

[0061] The peripheral portion 24 preferably includes the substrate 11 and a plurality of insulating layers formed above and below the substrate 11. More specifically, as shown in Figure 4, the first insulating layer 121, the second insulating layer 122, the third insulating layer 123, and the fourth insulating layer 124 are arranged above the substrate 11 in this order. The fifth insulating layer 125 and the sixth insulating layer 126 are arranged below the substrate 11 in this order.

[0062] The thermal conduction sensor 10 may or may not have a fifth insulating layer 125 and a sixth insulating layer 126. The presence or absence of the fifth insulating layer 125 and the sixth insulating layer 126 allows for adjustment of the stress applied to the substrate 11.

[0063] Next, the materials of each layer described above will be explained. The substrate 11 preferably contains silicon (Si). The plurality of insulating layers formed above and below the substrate 11 preferably contain silicon (Si) compounds from the viewpoint of availability, ease of formation, and chemical stability, and silicon dioxide (SiO ２ ) and silicon nitride (SiN ｘ It is more preferable that the first insulating layer 121, the third insulating layer 123, the fourth insulating layer 124 and the fifth insulating layer 125 include SiO ２Preferably, the second insulating layer 122 and the sixth insulating layer 126 are made of SiNx.

[0064] From the viewpoint of improving adhesion with the third insulating layer 123 and the fourth insulating layer 124, the first adhesion layer 33 and the second adhesion layer 34 preferably contain one or more selected from tantalum (Ta), titanium (Ti), titanium nitride, titanium oxide, titanium oxynitride, tantalum oxide, zirconium, zirconium oxide, yttrium, yttrium oxide, tungsten, tungsten oxide, chromium, chromium oxide, nickel, nickel oxide, and alloys thereof.

[0065] The material of the heat-generating resistor 31 is as previously described. The material of the pad 32 can be the same as the material of the heat-generating resistor 31. The heat-generating resistor 31 and the pad 32 may be made of different materials or the same material. From the viewpoint of enabling simple manufacturing and suppressing manufacturing costs, it is preferable that the heat-generating resistor 31 and the pad 32 are made of the same material.

[0066] In this embodiment, a thermal conduction sensor 10 with the configuration described above is used for explanation. However, the configuration of the thermal conduction sensor is not particularly limited in the concentration measurement method, flow rate measurement method, sensor module, control device, control method, and control program for these measurements in the present invention.

[0067] For example, the thermal conduction sensor 10 of this embodiment has a bridge 22, but it is not limited to this configuration, and the stage 21 may be directly connected to the peripheral portion 24 without a bridge 22.

[0068] Specifically, the thermal conduction sensor 10 can have the configuration shown in Figures 5 to 7. The thermal conduction sensor 10 shown in Figures 5 to 7 has basically the same configuration as the thermal conduction sensor 10 shown in Figures 2 to 4, and the same reference numerals are used for the same components, and their detailed explanations are omitted.

[0069] As shown in Figures 5 to 7, in this modified example, the thermal conduction sensor 10 has a first insulating layer 121, a second insulating layer 122, and a third insulating layer 123 that extend over the entire planar area of ​​the thermal conduction sensor 10. Furthermore, the fourth insulating layer 124 is also provided over the entire planar area of ​​the thermal conduction sensor 10, except for the area where the pad 32 is located. Due to this structure, the thermoelectric sensor 10 in this modified example does not have a bridge 22 and a bridge structure 20.

[0070] In other words, the thermal conduction sensor 10 has a diaphragm 26 equipped with a first insulator 121, a second insulator 122, a third insulator 123, and a fourth insulator 124, and a peripheral edge 24 surrounding the diaphragm 26, and a heat-generating resistor 31 is provided at any position in the thickness direction of the diaphragm 26. The diaphragm 26 is made of a thin film, and its thickness can be the same as the thickness of the stage 21 described above. The diaphragm 26 is rectangular, and the length of one side is preferably 100 μm or more and 4500 μm or less, more preferably 150 μm or more and 3000 μm or less, and even more preferably 200 μm or more and 1500 μm or less. However, the shape of the diaphragm 26 is not limited to a rectangle.

[0071] As shown in Figures 5 and 6, the heat conduction sensor 10 of this modified example has a heat-generating resistor 31 and two wires 312, 312 connecting the heat-generating resistor 31 to a pad 32. Each end of the heat-generating resistor 31 is connected to the respective ends of the two wires 312, 312, forming a single linear body as a whole.

[0072] In this modified example, when the material of the heat-generating resistor 31 and the wiring 312, 312 are the same, the portion of the wire that is densely packed due to meandering or the like is defined as the heat-generating resistor 31, and the portion extending outward from the heat-generating resistor 31 is defined as the wiring 312. The heat-generating resistor 31 is located approximately in the center of the diaphragm 26.

[0073] The control device 50 has a computer equipped with calculation means, storage means, communication means, etc., and is configured to control the voltage or current applied to the heating resistor 31 based on a control program stored in the storage means, acquire the voltage value, current value, and resistance value of the heating resistor 31 as detected values, and calculate at least one of the concentration of the target gas to be measured or the flow rate of the gas to be measured based on the acquired detected values.

[0074] As shown in Figure 1, the control device 50 includes a power supply unit 52 that supplies power to the heating resistor 31, a resistor measuring unit 54 that measures at least one of the resistance value of the heating resistor 31, the voltage value across the heating resistor 31, and the current value flowing through the heating resistor 31, a time control unit 56 that controls the time for the resistor measuring unit 54 to detect the voltage value, current value, and resistance value, and a calculation unit 58 that calculates at least one of the concentration of at least one type of target gas contained in the gas to be measured, or the flow rate of the gas to be measured, based on at least one of the resistance value, voltage value, and current value measured by the resistor measuring unit 54. The power supply unit 52 and the resistor measuring unit 54 can be realized by a resistance measuring instrument, such as a source meter, which is included in the control device 50. The time control unit 56 and the calculation unit 58 can be realized by a computer or the like incorporated into the control device 50.

[0075] The power supply unit 52 can generate heat in the heat-generating resistor 31 of the thermal conduction sensor 10 by supplying a predetermined amount of power to the heat-generating resistor 31. The resistance measurement unit 54 detects the voltage value across the heat-generating resistor 31 of the thermal conduction sensor 10, the current value flowing through the heat-generating resistor 31, or the resistance value of the heat-generating resistor 31 calculated based on the voltage value and the current value as a detected value. In the following embodiment, the example will basically describe the case in which the resistance value of the heat-generating resistor 31 is measured as the detected value.

[0076] In this embodiment, the control device 50 supplies first power to the heating resistor 31 with the power supply unit 52, measures time with the time control unit 56, and after a predetermined time has elapsed, the resistance value of the heating resistor 31 in the state where the first power has been supplied is acquired as the first detected value by the resistor measurement unit 54.

[0077] Here, the first power is not particularly limited, and it is sufficient to supply the minimum power necessary for the resistor measuring unit 54 to detect the voltage value across the heating resistor 31, the current value flowing through the heating resistor 31, and the resistance value of the heating resistor 31. Furthermore, by setting the predetermined time from supplying the first power to detecting the voltage value, current value, and resistance value of the heating resistor 31 as the first detected value, to the same time as the time from supplying the first power to detecting the resistance value of the heating resistor 31 as the first detected value when acquiring the correspondence relationship described later, accurate measurement can be performed.

[0078] Furthermore, the control device 50 supplies a second power to the heating resistor 31 via the power supply unit 52, measures time via the time control unit 56, and after a predetermined time has elapsed, the resistance value of the heating resistor 31 in the state where the second power has been supplied is acquired as a second detection value via the resistor measurement unit 54.

[0079] Here, the second power is not particularly limited as long as it is greater than the first power, but such a second power can be defined as the power at which the surface temperature of the heating resistor 31 reaches a predetermined temperature. From the viewpoint of accurately measuring the gas concentration and gas flow rate, the surface temperature of the heating resistor 31 is preferably 50°C to 800°C, and more preferably 400°C.

[0080] Furthermore, by setting the predetermined time from supplying the second power to detecting the voltage, current, and resistance values ​​of the heating resistor 31 as the second detection value to the same time as the time from supplying the second power to detecting the resistance value of the heating resistor 31 as the second detection value when acquiring the correspondence relationship described later, accurate measurements can be performed.

[0081] Furthermore, the predetermined time from supplying the first power to detecting the first detected value and the predetermined time from supplying the second power to detecting the second detected value do not need to be the same.

[0082] Based on the first and second detection values ​​obtained in this manner, the control device 50 uses a calculation unit 58 to calculate at least one of the concentration of the target gas contained in the gas being measured or the flow rate of the gas being measured.

[0083] Specifically, the system can calculate at least one of the following: the concentration of the target gas to be measured or the flow rate of the gas to be measured, based on the correspondence relationships created in advance and stored in the storage means of the control device 50, and the corrected detection value calculated from the second detection value.

[0084] The following shows the procedure for calculating the concentration of the target gas contained in the gas to be measured using the concentration measurement method in this embodiment. Note that the flow rate of the gas to be measured using the flow rate measurement method in this embodiment can also be calculated using essentially the same method.

[0085] In this embodiment, a calibration curve is used to show the correspondence, but it is not limited to this; for example, a comparison table showing the comparative relationship between two values ​​can also be created and used.

[0086] <First Method> First, the sensor module 1 is used to supply the first power, and after a predetermined time has elapsed, the first detected value of the heating resistor 31 is obtained. By performing this at each temperature, a calibration curve 1A showing the correspondence between the first detected value and the temperature is obtained.

[0087] Next, after supplying a second power supply using the sensor module 1, a second detection value of the heating resistor 31 is obtained after a predetermined time has elapsed. By performing this at each temperature, a calibration curve 1B showing the correspondence between the second detection value and the temperature is obtained.

[0088] Next, at a predetermined ambient temperature, for a gas to be measured whose concentration is known, the sensor module 1 is used to supply a second power supply, and after a predetermined time has elapsed, the second detection value of the heating resistor 31 is acquired. By performing this while changing the concentration of the gas to be measured, a calibration curve 1C showing the correspondence between the concentration and the second detection value is obtained.

[0089] Calibration curve 1C, which shows the correspondence between the concentration of the gas under test and the second detection value, is created by acquiring measurement points (hereinafter simply referred to as "measurement points") that show the relationship between the concentration and the second detection value within the desired concentration range for measurement, and / or by acquiring three or more measurement points. By acquiring measurement points in this way and creating calibration curve 1C, high-precision concentration measurement can be performed.

[0090] This completes the acquisition of the calibration curve necessary for concentration measurement. When actually measuring the concentration of the target gas contained in the gas to be measured, first, the sensor module 1 is used to supply first power, and then, after a predetermined time has elapsed, the first detected value of the heating resistor 31 is acquired. The temperature is then calculated using the first detected value acquired here and the calibration curve 1A.

[0091] Next, after supplying a second power supply using the sensor module 1, a second detection value of the heat-generating resistor 31 is obtained after a predetermined time has elapsed. Using the second detection value obtained here, the calibration curve 1B, and the calculated temperature, a corrected detection value, which is the second detection value at a predetermined ambient temperature, is calculated.

[0092] Then, using the corrected detection value and calibration curve 1C, the concentration of the target gas contained in the measured gas can be calculated.

[0093] <Second Method> First, the sensor module 1 is used to supply the first power, and after a predetermined time has elapsed, the first detected value of the heating resistor 31 is obtained. By performing this at each temperature, a calibration curve 2A showing the correspondence between the first detected value and the temperature is obtained.

[0094] Next, the sensor module 1 is used to supply a second power supply, and after a predetermined time has elapsed, the second detected value of the heating resistor 31 is obtained. By performing this at each temperature, a calibration curve 2B showing the correspondence between the second detected value and the temperature is obtained.

[0095] Next, for a gas whose concentration is known at multiple ambient temperatures, the sensor module 1 is used to supply a second power supply, and after a predetermined time has elapsed, the second detection value of the heating resistor 31 is acquired. By performing this while changing the concentration of the gas to be measured, multiple calibration curves 2C at each ambient temperature that show the correspondence between the concentration and the second detection value are acquired.

[0096] Calibration curve 2C, which shows the correspondence between the concentration of the gas under test and the second detection value, is created by acquiring measurement points (hereinafter simply referred to as "measurement points") that show the relationship between the concentration and the second detection value within the desired concentration range for measurement, or by acquiring three or more measurement points, or by acquiring measurement points that satisfy both conditions. By acquiring measurement points in this way and creating calibration curve 2C, high-precision concentration measurement can be performed.

[0097] This completes the acquisition of the calibration curve necessary for concentration measurement. When actually measuring the concentration of the target gas contained in the gas to be measured, first, the sensor module 1 is used to supply first power, and then, after a predetermined time has elapsed, the first detected value of the heating resistor 31 is acquired. The temperature is then calculated using the first detected value acquired here and the calibration curve 2A.

[0098] Next, after supplying a second power supply using the sensor module 1, a second detection value of the heat-generating resistor 31 is obtained after a predetermined time has elapsed. Subsequently, the concentration of the gas to be measured can be calculated using the following two methods.

[0099] (Method 1) Using the acquired second detection value, the calculated temperature, and calibration curve 2B, a corrected detection value is calculated, which is the second detection value at the ambient temperature of calibration curve 2C acquired at the temperature closest to the calculated temperature. Then, using the corrected detection value and the selected calibration curve 2C, the concentration of the target gas contained in the gas being measured can be calculated.

[0100] (Method 2) Using multiple calibration curves 2C and the calculated temperature, a calibration curve 2C' corresponding to the calculated temperature is calculated. Then, using calibration curve 2C' and the acquired second detection value, the concentration of the target gas contained in the gas being measured can be calculated. In this way, by acquiring calibration curves 2C for multiple ambient temperatures, concentration measurements can be performed with higher accuracy compared to the first method.

[0101] <Third Method> First, the sensor module 1 is used to supply first power, and then, after a predetermined time has elapsed, the first detected value of the heat-generating resistor 31 is obtained. Next, the sensor module 1 is used to supply second power, and then, after a predetermined time has elapsed, the second detected value of the heat-generating resistor 31 is obtained.

[0102] By acquiring the first and second detection values ​​at each temperature, a calibration curve 3A showing the correspondence between the first and second detection values ​​is obtained.

[0103] Next, at a predetermined ambient temperature, for a gas to be measured whose concentration is known, the sensor module 1 is used to supply a second power supply, and after a predetermined time has elapsed, the second detection value of the heating resistor 31 is acquired. By performing this while changing the concentration of the gas to be measured, a calibration curve 3B showing the correspondence between the concentration and the second detection value is acquired. At this time, the first detection value corresponding to the predetermined ambient temperature is also acquired.

[0104] Calibration curve 3B, which shows the correspondence between the concentration of the gas under test and the second detection value, is created by acquiring measurement points (hereinafter simply referred to as "measurement points") that show the relationship between the concentration and the second detection value within the desired concentration range for measurement, or by acquiring three or more measurement points, or by acquiring measurement points that satisfy both conditions. By acquiring measurement points in this way and creating calibration curve 3B, high-precision concentration measurement can be performed.

[0105] This completes the acquisition of the calibration curve necessary for concentration measurement. When actually measuring the concentration of the target gas contained in the gas to be measured, first, the sensor module 1 is used to supply first power, and after a predetermined time has elapsed, the first detection value of the heating resistor 31 is acquired. Then, second power is supplied, and after a predetermined time has elapsed, the second detection value of the heating resistor 31 is acquired.

[0106] Using the first and second detection values ​​of the target gas being measured, calibration curve 3A, and the first detection value corresponding to calibration curve 3B, i.e., the first detection value corresponding to a predetermined ambient temperature, a corrected detection value is calculated, which is the second detection value assuming the target gas was at a predetermined ambient temperature. When correcting the second detection value in this way, accurate concentration measurement can be achieved by correcting the acquired second detection value using a second detection value within the range that can be taken on calibration curve 3B as the "reference detection value".

[0107] Then, using the corrected detection value and calibration curve 3B, the concentration of the target gas contained in the measured gas can be calculated.

[0108] <Fourth Method> First, the sensor module 1 is used to supply first power, and then, after a predetermined time has elapsed, the first detected value of the heat-generating resistor 31 is obtained. Next, the sensor module 1 is used to supply second power, and then, after a predetermined time has elapsed, the second detected value of the heat-generating resistor 31 is obtained.

[0109] By acquiring the first and second detection values ​​at each temperature, a calibration curve 4A showing the correspondence between the first and second detection values ​​is obtained.

[0110] Next, for a gas whose concentration is known at multiple ambient temperatures, the sensor module 1 is used to supply a second power supply, and after a predetermined time has elapsed, the second detection value of the heating resistor 31 is acquired. By performing this while changing the concentration of the gas to be measured, a calibration curve 4B showing the correspondence between the concentration and the second detection value is obtained. At this time, the first detection values ​​corresponding to multiple ambient temperatures are also acquired.

[0111] Calibration curve 4B, which shows the correspondence between the concentration of the gas under test and the second detection value, is created by acquiring measurement points (hereinafter simply referred to as "measurement points") that show the relationship between the concentration and the second detection value within the desired concentration range for measurement, or by acquiring three or more measurement points, or by acquiring measurement points that satisfy both conditions. By acquiring measurement points in this way and creating calibration curve 4B, high-precision concentration measurement can be performed.

[0112] This completes the acquisition of the calibration curve necessary for concentration measurement. When actually measuring the concentration of the target gas contained in the gas to be measured, first, the sensor module 1 is used to supply first power, and after a predetermined time has elapsed, the first detection value of the heating resistor 31 is acquired. Then, second power is supplied, and after a predetermined time has elapsed, the second detection value of the heating resistor 31 is acquired.

[0113] Next, from among the calibration curves 4B obtained in advance at multiple ambient temperatures, the calibration curve 4B that shows the first detection value closest to the first detection value of the gas to be measured is selected. Then, using the first and second detection values ​​of the gas to be measured, calibration curve 4A, and the first detection value corresponding to the selected calibration curve 4B, the corrected detection value, which is the second detection value at the ambient temperature corresponding to the selected calibration curve 4B, is calculated. When correcting the second detection value in this way, accurate concentration measurement can be performed by correcting the acquired second detection value using a second detection value within the range that can be taken in the selected calibration curve 4B as the "reference detection value".

[0114] Then, using the corrected detection value and the selected calibration curve 4B, the concentration of the target gas contained in the measured gas can be calculated. In this way, by acquiring calibration curve 4B for multiple ambient temperatures, concentration measurements can be performed with higher accuracy compared to the first method.

[0115] Basically, by obtaining the corresponding relationships such as calibration curves based on the methods described above, the concentration of the target gas and the flow rate of the target gas can be calculated based on the calibration curve between the second detection value at one or more ambient temperatures obtained in advance and the concentration of the target gas, and the corrected detection value. It should be noted that the calculation procedure can be changed as long as it is based on the methods described above.

[0116] For example, in the third method described above, the first detection value, the second detection value, and the calibration curve 3A are used to calculate the corrected detection value, which is the second detection value at a predetermined ambient temperature. However, it is also possible to create a calibration curve 3B' of the corrected detection value for each concentration by calculating the corrected detection value for each concentration by subtracting the first detection value from the second detection value for each concentration. (Hereafter, this correction method will also be called differential correction.)

[0117] When performing concentration measurements, the first detection value is subtracted from the second detection value to calculate a corrected detection value. This corrected detection value, along with calibration curve 3B', can then be used to calculate the concentration of the target gas contained in the measured gas.

[0118] In the above embodiment, the corrected detection value is calculated by subtracting the first detection value from the second detection value, but the method for calculating the corrected detection value is not limited to this.

[0119] For example, first, the sensor module 1 is used to supply a first power supply, and after a predetermined time has elapsed, a first detected value of the heating resistor 31 is obtained. Next, for a gas to be measured whose concentration is known, the sensor module 1 is used to supply a second power supply, and after a predetermined time has elapsed, a second detected value of the heating resistor 31 is obtained. Then, the ratio of the first detected value to the second detected value is calculated.

[0120] By repeatedly performing the acquisition of the first detected value, the acquisition of the second detected value, and the calculation of the ratio between the first and second detected values ​​for a predetermined period of time, the mean or median of the ratio between the first and second detected values ​​can be obtained.

[0121] Here, if the second detection value obtained first is the initial value R0, the mean or median of the ratio of the first detection value to the second detection value is the coefficient a, the first detection value is R1, and the second detection value is R2, then the corrected detection value R C R can be calculated as follows: C = R2 - a × R1 + R0

[0122] In the above embodiment, the second detection value obtained first is used as the initial value R0, but any fixed value is acceptable, and it is also acceptable to use any value.

[0123] Furthermore, a calibration curve showing the relationship between the first and second detection values ​​can be created by repeatedly obtaining the first and second detection values ​​for a predetermined period of time. When creating the calibration curve, either a first-order or second-order approximation may be used. By using the coefficients obtained from creating the calibration curve in this way, the corrected detection value can be calculated.

[0124] When the calibration curve is defined using a first-order approximation, the first detection value obtained is the initial value R. 10 If the first detection value is R1, the second detection value is R2, and the equation of the first approximation line is R2 = b × R1 + c, then the corrected detection value R C This can be calculated as follows. (Hereafter, this correction method will also be called the first-order approximation correction.) R C = R2 - b × (R1 - R 10 )

[0125] Furthermore, if the calibration curve is defined by a quadratic approximation, the first detection value obtained is the initial value R. 10 Let R1 be the first detection value, R2 be the second detection value, and the equation of the quadratic approximation line be R2 = d × R1 2 If we set it as +e × R1 + f, then the corrected detected value R C This can be calculated as follows. (Hereafter, this correction method will also be called the second-order approximation correction.) R C =R2-(d×(R1-R 10 ) 2 +e × (R1 - R 10 ) + f)

[0126] <Example> Figure 8 is a graph showing the corrected detection value when measuring oxygen gas of known concentration using the sensor module 1 shown in Figure 1. The corrected detection value in Figure 8 is calculated by differential correction.

[0127] Here, the first detected value is the resistance value of the heating resistor 31 at room temperature, and the second detected value is the resistance value of the heating resistor 31 when the surface temperature of the heating resistor 31 is 400°C.

[0128] As shown in Figure 8, the corrected detected value exhibits high linearity with respect to the oxygen concentration, and by performing measurements using the calibration curve described above, the concentration can be measured with high accuracy. Furthermore, Figure 8 shows the results when the predetermined time from supplying the first power to detecting the resistance value of the heating resistor 31 as the first detected value and the predetermined time from supplying the second power to detecting the resistance value of the heating resistor 31 as the second detected value are 1 second, 5 seconds, 10 seconds, 30 seconds, 60 seconds, 180 seconds, and 300 seconds, respectively, and it can be confirmed that linearity is ensured at each time.

[0129] Figure 9 is a graph showing the change in the corrected detected value over time. The corrected detected value in Figure 9 is calculated using first-order approximation correction.

[0130] Here, the first detected value is the resistance value of the heating resistor 31 at room temperature, and the second detected value is the resistance value of the heating resistor 31 when the surface temperature of the heating resistor 31 is 400°C.

[0131] As shown in Figure 9, even when the thermal conduction sensor is used continuously, the effects of drift of the heat-generating resistor and the ambient temperature are compensated for, and the corrected detected value remains almost unchanged. This indicates that the sensor module 1 of the present invention compensates for the effects of changes in the heat-generating resistor over time and changes in ambient temperature, enabling accurate measurement of gas concentration and flow rate over a long period of time, thus improving the durability and accuracy of the sensor.

[0132] Furthermore, Figure 9 shows the results when the predetermined time from supplying the first power to detecting the resistance value of the heating resistor 31 as the first detected value, and the predetermined time from supplying the second power to detecting the resistance value of the heating resistor 31 as the second detected value, are set to 20 seconds, 40 seconds, 70 seconds, 190 seconds, and 310 seconds, respectively. It can be confirmed that the corrected detected value is almost constant at each time.

[0133] Figure 10 is a graph showing the detected values ​​when measuring a nitrogen-carbon dioxide mixed gas using the sensor module shown in Figure 1. In this embodiment, the resistance value of the heating resistor 31 is used as the detected value.

[0134] Specifically, Figure 10(a) is a graph showing the relationship between the usage time of the sensor module and the second detected value, Figure 10(b) is a graph showing the relationship between the usage time of the sensor module and the corrected detected value calculated by first-order approximation correction, and Figure 10(c) is a graph showing the relationship between the usage time of the sensor module and the corrected detected value calculated by second-order approximation correction.

[0135] Even when the gas being measured is a nitrogen-carbon dioxide mixture, as shown in Figure 10(a), without correction, the detected value fluctuates significantly with the usage time of the sensor module. In contrast, as shown in Figures 10(b) and (c), by correcting the detected value, a constant detected value can be obtained regardless of the usage time of the sensor module. In other words, the gas concentration and flow rate can be accurately measured over a long period of time without being affected by the aging of the heat-generating resistor, thus improving the durability of the sensor.

[0136] Figure 11 is a graph showing the detected values ​​when measuring a nitrogen-carbon dioxide mixed gas using the sensor module shown in Figure 1. In this embodiment, the voltage value across the heating resistor 31 is used as the detected value.

[0137] Specifically, Figure 11(a) is a graph showing the relationship between the usage time of the sensor module and the second detected value, Figure 11(b) is a graph showing the relationship between the usage time of the sensor module and the corrected detected value calculated by first-order approximation correction, and Figure 11(c) is a graph showing the relationship between the usage time of the sensor module and the corrected detected value calculated by second-order approximation correction.

[0138] Even when the detected value is defined as the voltage across the heating resistor 31, as shown in Figure 11(a), if no correction is performed, the detected value fluctuates with the usage time of the sensor module. In contrast, as shown in Figures 11(b) and (c), by correcting the detected value, a constant detected value can be obtained regardless of the usage time of the sensor module. In other words, gas concentration and flow rate can be accurately measured over a long period of time without being affected by the aging of the heating resistor, thus improving the durability of the sensor.

[0139] Figure 12 is a graph showing the detected values ​​when measuring a nitrogen-argon mixed gas using the sensor module shown in Figure 1. Specifically, Figure 12(a) is a graph showing the relationship between the usage time of the sensor module and the second detected value, Figure 12(b) is a graph showing the relationship between the usage time of the sensor module and the corrected detected value calculated by first-order approximation correction, and Figure 12(c) is a graph showing the relationship between the usage time of the sensor module and the corrected detected value calculated by second-order approximation correction.

[0140] Even when the gas being measured is a nitrogen-argon mixture, as shown in Figure 12(a), without correction, the detected value fluctuates significantly with the usage time of the sensor module. In contrast, as shown in Figures 12(b) and (c), by correcting the detected value, a constant detected value can be obtained regardless of the usage time of the sensor module. In other words, the gas concentration and flow rate can be accurately measured over a long period of time without being affected by the aging of the heat-generating resistor, thus improving the durability of the sensor.

[0141] Thus, the sensor module of the present invention can obtain stable detection values ​​over a long period of time, regardless of the type of gas being measured, by correcting for the effects of changes in the heat-generating resistance element over time, and can accurately measure gas concentration and flow rate, in other words, it can improve the durability of the sensor.

[0142] In this invention, the gas whose concentration is directly measured is limited to one type. However, if the gas to be measured contains three or more types of gases, and the concentrations of two of the gases are unknown while the concentrations of the other gases are fixed, the present invention can be used to measure the concentrations.

[0143] Similarly, a calibration curve for calculating the flow rate of the gas being measured can also be created by obtaining the second detection value at each flow rate and the second detection value at each temperature, and then calculating the corrected detection value at each flow rate and the corrected detection value at each temperature.

[0144] Furthermore, in this invention, the measurement accuracy can be further improved by using calibration curves acquired for each external temperature (ambient temperature) when calculating the concentration or flow rate of the gas to be measured. Specifically, first, a calibration curve showing the relationship between the first detected value and the ambient temperature is acquired. Next, a calibration curve showing the relationship between the second detected value and the concentration or flow rate is acquired for each ambient temperature.

[0145] This allows for the calculation of a corrected detection value from the acquired first and second detection values, and the calculation of the ambient temperature from the acquired first detection value. Then, the concentration or flow rate of the target gas can be calculated from the corrected detection value as the second detection value on a calibration curve that shows the relationship between the second detection value and the concentration or flow rate for each ambient temperature.

[0146] Since it is practically difficult to obtain calibration curves for all ambient temperatures in advance, calculations can be performed using calibration curves obtained beforehand for multiple ambient temperatures. For example, if the ambient temperature at the time of measurement is T, the concentration or flow rate of the gas being measured at ambient temperature T can be calculated by using the calibration curve at ambient temperature T1, which is lower than T, and the calibration curve at ambient temperature T2, which is higher than T.

[0147] Specifically, if MT1 is the calculated value (concentration or flow rate of the gas being measured) at ambient temperature T1, and MT2 is the calculated value at ambient temperature T2, then the calculated value MT at ambient temperature T can be calculated as follows: MT = MT1 + (MT2 - MT1) / (T2 - T1) × (T - T1)

[0148] Figure 13 is a graph showing the error between the supplied oxygen concentration and the calculated oxygen concentration when measuring oxygen concentration using the sensor module shown in Figure 1. Specifically, in the graph shown in Figure 13(a), the corrected detected value is calculated using only the calibration curve at an ambient temperature of 25°C, and the calculated oxygen concentration is calculated based on this. On the other hand, in the graph shown in Figure 13(b), the calculated oxygen concentration is calculated by performing a correction based on the ambient temperature by acquiring calibration curves for each ambient temperature.

[0149] As shown in Figure 17, without correction, the error exceeds 50%, whereas with correction, as shown in Figure 13(a), the error is within ±4%. Furthermore, Figure 13(a) shows that the effect of ambient temperature can be corrected even with only the calibration curve for an ambient temperature of 25°C, while as shown in Figure 13(b), by using a calibration curve based on ambient temperature, the oxygen concentration can be calculated more accurately, with the error within ±0.4%.

[0150] <Comparative Example> As a calibration curve showing the correspondence between the concentration at a given ambient temperature and the corrected detected value, an example is shown where the corrected detected value was calculated for two points where the oxygen concentration was 0% and 25%. Figure 14 is a graph showing the relationship between the supplied oxygen concentration and the corrected detected value at an ambient temperature of 25°C.

[0151] When oxygen concentration was actually detected using the sensor module shown in Figure 1 with this calibration curve, as shown in Figure 15, the oxygen concentration could be calculated accurately within the concentration range for which the calibration curve was obtained. However, outside the concentration range for which the calibration curve was obtained, i.e., when the supplied oxygen concentration was 50% and 100%, the measurement accuracy decreased significantly.

[0152] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications are possible without departing from the object of the present invention.

[0153] 1 Sensor module 10 Thermal conduction sensor 11 Substrate 121 First insulating layer 122 Second insulating layer 123 Third insulating layer 124 Fourth insulating layer 125 Fifth insulating layer 126 Sixth insulating layer 14 Control device 20 Bridge structure 21 Stage 22 Bridge 24 Peripheral part 26 Diaphragm 31 Heat-generating resistor 312 Wiring 32 Wire bonding pad 32 Pad 33 First contact layer 34 Second contact layer 50 Control device 52 Power supply unit 54 Resistance measurement unit 56 Time control unit 58 Calculation unit

Claims

1. A concentration measurement method for measuring the concentration of a target gas contained in a gas to be measured using a thermal conduction sensor having a heat-generating resistor that generates heat when an electric current is applied, the method comprising: firstly, a first detected value of the heat-generating resistor after a predetermined time has elapsed after supplying a first power; secondly, a second detected value of the heat-generating resistor after a predetermined time has elapsed after supplying a second power greater than the first power; correcting the second detected value using two correspondences, one between the first detected value and the ambient temperature and the other between the second detected value and the ambient temperature, which have been acquired in advance, or using the correspondence between the first detected value and the second detected value which have been acquired in advance; acquiring measurement points that show the relationship between the second detected value and the concentration of the target gas at one or more ambient temperatures acquired in advance, within a desired concentration range for which measurement is to be performed, and / or acquiring three or more of the measurement points to create a calibration curve between the second detected value and the concentration of the target gas, and the corrected second detected value, in order to calculate the concentration of the target gas contained in the gas to be measured.

2. The concentration measurement method according to claim 1, wherein the correspondence is a calibration curve.

3. The concentration measurement method according to claim 1, wherein the concentration of the target gas contained in the target gas is calculated based on a calibration curve of the second detection values ​​for each ambient temperature obtained in advance and the concentration of the target gas, and the corrected second detection values.

4. The concentration measurement method according to claim 1, wherein the second power is the power at which the surface temperature of the heating resistor reaches a predetermined temperature.

5. The concentration measurement method according to claim 4, wherein the predetermined temperature is 50°C to 800°C.

6. The thermal conduction sensor comprises a heat-generating resistor that generates heat when an electric current is applied, and a stage that supports the heat-generating resistor, wherein the heat-generating resistor overlaps with the stage in a plan view, and the area S of the stage in a plan view is 3.6 × 10 ７ μm ２ The following applies, where V is the total volume of the heating resistor and the stage, and S / V is 0.0010 μm －１ 10 μm or more －１ The concentration measurement method according to claim 1, which is as follows:

7. A flow rate measurement method for measuring the flow rate of a gas to be measured using a thermal conduction sensor having a heat-generating resistor that generates heat when an electric current is applied, the method comprising: firstly, after supplying a first power and a predetermined time has elapsed, a first detected value of the heat-generating resistor; secondly, after supplying a second power greater than the first power and a predetermined time has elapsed, a second detected value of the heat-generating resistor; correcting the second detected value using two correspondences, one or the other, obtained in advance, between the first detected value and the ambient temperature, or using the correspondence between the first detected value and the second detected value, and calculating the flow rate of the gas to be measured based on a calibration curve obtained in advance between the second detected value and the flow rate of the gas to be measured at one or more ambient temperatures, and the corrected second detected value.

8. The flow rate measurement method according to claim 7, wherein the aforementioned correspondence is a calibration curve.

9. A flow rate measurement method according to claim 7, wherein the flow rate of the gas to be measured is calculated based on a calibration curve between the second detected value and the flow rate of the gas to be measured, created by acquiring measurement points in a desired flow rate range for which measurement is to be performed, and / or by acquiring three or more of the measurement points, and the corrected second detected value.

10. The flow rate measurement method according to claim 7, wherein the second power is the power at which the surface temperature of the heating resistor reaches a predetermined temperature.

11. The flow rate measurement method according to claim 10, wherein the predetermined temperature is 50°C to 800°C.

12. The thermal conduction sensor comprises a heat-generating resistor that generates heat when an electric current is applied, and a stage that supports the heat-generating resistor, wherein the heat-generating resistor overlaps with the stage in a plan view, and the area S of the stage in a plan view is 3.6 × 10 ７ μm ２ The following applies, where V is the total volume of the heating resistor and the stage, and S / V is 0.0010 μm －１ 10 μm or more －１ The flow rate measurement method according to claim 7, which is as follows:

13. A sensor module for measuring at least one of the concentration of at least one target gas contained in a gas to be measured, or the flow rate of the gas to be measured, comprising: a thermal conduction sensor having a heat-generating resistor that generates heat when energized; and a control device configured to control the application of voltage or current to the thermal conduction sensor and to acquire the resistance value of the heat-generating resistor from the thermal conduction sensor, wherein the control device acquires a first detected value of the heat-generating resistor after a predetermined time has elapsed since supplying a first power to the heat-generating resistor, acquires a second detected value of the heat-generating resistor after a predetermined time has elapsed since supplying a second power greater than the first power to the heat-generating resistor, corrects the second detected value using two correspondences: the correspondence between the first detected value and the ambient temperature acquired in advance and the correspondence between the second detected value and the ambient temperature acquired in advance, or using the correspondence between the first detected value and the second detected value acquired in advance. A sensor module that calculates the concentration of the gas to be measured based on a calibration curve between the second detected value and the concentration of the gas to be measured, created by acquiring measurement points in a desired concentration range for measurement, and / or by acquiring three or more of the measurement points, and the corrected second detected value, and / or by acquiring measurement points in a desired flow rate range for measurement, and / or by acquiring three or more of the measurement points, and the corrected second detected value, and / or by calculating the flow rate of the gas to be measured, and 14. The sensor module according to claim 13, wherein the correspondence is a calibration curve. 15.A control device for measuring at least one of the concentration of at least one target gas contained in a gas to be measured, or the flow rate of a gas to be measured, using a thermal conduction sensor having a heat-generating resistor that generates heat when an electric current is applied, comprising: a power supply unit that supplies predetermined power to the heat-generating resistor; a resistor measurement unit that measures at least one of the resistance value of the heat-generating resistor, the voltage value across the ends of the heat-generating resistor, or the current value flowing through the heat-generating resistor; a time control unit that controls the time for the resistor measurement unit to detect the resistance value; and a calculation unit that calculates at least one of the concentration of at least one target gas contained in the gas to be measured, or the flow rate of a gas to be measured, based on the resistance value detected by the resistor measurement unit, wherein the calculation unit supplies first power to the heat-generating resistor by the power supply unit, measures time by the time control unit, and obtains a first detected value of the heat-generating resistor detected by the resistor measurement unit after a predetermined time has elapsed. The power supply unit supplies a second power greater than the first power to the heating resistor, the time control unit measures time, and after a predetermined time has elapsed, the resistor measurement unit obtains the second detected value of the heating resistor. The second detected value is corrected using two correspondences: the correspondence between the previously obtained first detected value and the ambient temperature, and the correspondence between the previously obtained second detected value and the ambient temperature, or using the correspondence between the previously obtained first detected value and the second detected value. A control device that calculates the concentration of the target gas contained in the target gas based on a calibration curve created by acquiring measurement points in a desired concentration range for measurement, and / or acquiring three or more of the aforementioned measurement points, which show the relationship between the second detected value and the concentration of the target gas at one or more previously acquired ambient temperatures, and the corrected second detected value; and / or calculates the flow rate of the target gas based on a calibration curve created by acquiring measurement points in a desired flow rate range for measurement, and / or acquiring three or more of the aforementioned measurement points, which show the relationship between the second detected value and the flow rate of the target gas at one or more previously acquired ambient temperatures, and the corrected second detected value.

16. A control method for controlling a control device that measures at least one of the concentration of at least one target gas contained in a gas to be measured, or the flow rate of a gas to be measured, using a thermal conduction sensor having a heat-generating resistor that generates heat when an electric current is applied, the method comprising: a step of supplying a first power to the heat-generating resistor in the thermal conduction sensor, and then acquiring a first detected value of the heat-generating resistor after a predetermined time has elapsed; a step of supplying a second power greater than the first power to the heat-generating resistor in the thermal conduction sensor, and then acquiring a second detected value of the heat-generating resistor after a predetermined time has elapsed; and a step of correcting the second detected value using two correspondence relationships, namely the correspondence relationship between the first detected value and the ambient temperature acquired in advance and the correspondence relationship between the second detected value and the ambient temperature acquired in advance, or using the correspondence relationship between the first detected value and the second detected value acquired in advance. A control method comprising the steps of: acquiring measurement points in a desired concentration range for which measurement is to be performed, with respect to a relationship between a second detected value and the concentration of the gas to be measured, with respect to measurement points that show the relationship between a second detected value and the concentration of the gas to be measured, with respect to measurement points that show the relationship between a second detected value and the concentration of the gas to be measured, with respect to measurement points that show the relationship between a second detected value and the flow rate respect to a desired flow rate range for which measurement is to be performed, with respect to measurement points that show respect to a relationship between a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a relationship between a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a relationship between a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a desired flow rate range for which measurement is to be performed, with respect to measurement points that show respect to a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a relationship between a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a desired flow rate for which measurement is to be performed, with respect to measurement points that show respect to a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a second detected value and the flow rate of the gas to be measured, with respect to measurement points that show respect to a second detected value and the concentration of the gas to be measured, with respect to 17. A control program for measuring at least one of the concentrations of at least one target gas contained in a gas to be measured, or the flow rate of a gas to be measured, using a thermal conduction sensor having a heat-generating resistor that generates heat when an electric current is applied, comprising: a step of supplying a first power to the heat-generating resistor and then acquiring a first detected value of the heat-generating resistor after a predetermined time has elapsed; a step of supplying a second power greater than the first power to the heat-generating resistor and then acquiring a second detected value of the heat-generating resistor after a predetermined time has elapsed; and a step of correcting the second detected value using two correspondence relationships, namely the correspondence relationship between the first detected value and the ambient temperature acquired in advance and the correspondence relationship between the second detected value and the ambient temperature acquired in advance, or using the correspondence relationship between the first detected value and the second detected value acquired in advance. A control program that causes the program to execute the following steps: acquiring measurement points in a desired concentration range for which measurement is to be performed, for measurement points that show the relationship between a second detected value and the concentration of the gas to be measured, which have been acquired in advance at one or more ambient temperatures; and / or calculating the concentration of the gas to be measured based on a calibration curve between the second detected value and the concentration of the gas to be measured, created by acquiring three or more of the measurement points, and the corrected second detected value; and / or calculating the flow rate of the gas to be measured based on a calibration curve between the second detected value and the flow rate of the gas to be measured, created by acquiring three or more of the measurement points that show the relationship between a second detected value and the flow rate of the gas to be measured, which have been acquired in advance at one or more ambient temperatures, and the corrected second detected value.

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