Physical Quantity Measurement System

Abstract

The present disclosure addresses the problem of more accurately measuring steam pressure in a mixed gas even when the mixed gas is flowing in a flow passage in an environment under high humidity. The physical quantity measurement system (1) is provided with a temperature / humidity sensor (16), a heat generation unit (17), a heat generation control unit (203), and a steam pressure measurement unit (204). The heat generation unit (17) performs a heat generation operation for generating heat for heating the temperature / humidity sensor (16). The steam pressure measurement unit (204) measures the steam pressure of the steam contained in the mixed gas. The heat generation control unit (203) performs on / off control on the heat generation unit (17) on the basis of the result of a comparison between a humidity measurement value measured by the temperature / humidity sensor (16) and a threshold value. The steam pressure measurement unit (204) measures the steam pressure of the steam on the basis of the humidity measurement value and a temperature measurement value measured by the temperature / humidity sensor (16) regardless of the state of the heat generation unit (17).

Description

[Technical Field]

[0001] The present disclosure generally relates to a physical quantity measurement system, and more particularly to a physical quantity measurement system that measures a gas mixture flowing through a flow path. [Background technology]

[0002] BACKGROUND ART Conventionally, a fuel cell system, for example, is known as a system that uses a physical quantity measurement system that measures the hydrogen concentration in a flow path through which a mixed gas containing hydrogen (mixed gas) flows (see Patent Document 1).

[0003] In the fuel cell system of Patent Document 1, when a mixed gas containing three components, namely hydrogen, water vapor, and impurity gas, flows through a flow path, a hygrometer is provided and the water vapor concentration is determined using the detection results of the hygrometer.

[0004] When determining the water vapor concentration from a mixed gas containing three components: hydrogen, water vapor, and impurity gases, one method is to first measure the water vapor pressure using the detection results (humidity) measured by a hygrometer. When a system (physical quantity measurement system) that measures a physical quantity (e.g., water vapor concentration) is used in a high-humidity environment, condensation may occur on the hygrometer. If condensation occurs, the accuracy of the humidity measurement by the hygrometer decreases, which results in a problem of a decrease in the accuracy of the water vapor pressure measurement. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-317752 Summary of the Invention

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a physical quantity measurement system that can more accurately measure the water vapor pressure in a mixed gas even when the mixed gas flows through a flow path in a high-humidity environment.

[0007] A physical quantity measurement system according to one aspect of the present disclosure includes a temperature and humidity sensor, a heat generating unit, a heat generation control unit, and a water vapor pressure measurement unit. The temperature and humidity sensor measures the humidity and temperature of a mixed gas flowing through a flow path. The heat generating unit performs a heat generating operation to generate heat to warm the temperature and humidity sensor. The heat generation control unit performs on / off control on the heat generating unit to switch the state of the heat generating unit between an on state in which the heat generating operation is performed and an off state in which the heat generating operation is stopped. The water vapor pressure measurement unit measures the water vapor pressure of water vapor contained in the mixed gas. The heat generation control unit performs the on / off control on the heat generating unit based on a comparison result between a humidity measurement value of the mixed gas measured by the temperature and humidity sensor and a threshold value. The water vapor pressure measurement unit measures the water vapor pressure of the water vapor contained in the mixed gas based on the humidity measurement value and a temperature measurement value of the mixed gas measured by the temperature and humidity sensor, regardless of the state of the heat generating unit. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing the configuration of a physical quantity measuring system according to an embodiment. [Figure 2] FIG. 2 is a system diagram showing the configuration of the physical quantity measuring system. [Figure 3] FIG. 3 is a cross-sectional view of a flow path main body provided in the physical quantity measuring system in the XZ plane. [Figure 4] FIG. 4 is a cross-sectional view of the flow path main body provided in the physical quantity measuring system in the XY plane. [Figure 5] FIG. 5 is a flowchart showing the operation of the physical quantity measuring system. [Figure 6] FIG. 6 is a flowchart showing a heat generation control process performed by the physical quantity measuring system. [Figure 7] FIG. 7 is a flowchart showing a third measurement process performed by the physical quantity measurement system. [Figure 8] FIG. 8 is a flowchart showing a first abnormality detection process performed by the physical quantity measuring system. [Figure 9]FIG. 9 is a flowchart showing a second abnormality detection process performed by the physical quantity measuring system. [Figure 10] FIG. 10 is a flowchart showing a concentration measurement process performed by the physical quantity measurement system. [Figure 11] FIG. 11 is a flowchart showing the sound speed calculation process performed in the concentration measurement process in the same embodiment. [Figure 12] FIG. 12 is a flowchart showing the hydrogen concentration calculation process performed in the concentration measurement process. [Figure 13] FIG. 13 is a flowchart showing a flow rate measurement process performed by the physical quantity measurement system. [Figure 14] FIG. 14 is a flowchart showing a flow coefficient calculation process performed in the flow measurement process in the same embodiment. [Figure 15] FIG. 15 is a flowchart showing a relative humidity measurement process performed by the physical quantity measurement system. [Figure 16] FIG. 16 is a flowchart showing the third measurement process in the first modification. DETAILED DESCRIPTION OF THE INVENTION

[0009] The embodiments and modifications described below are merely examples of the present disclosure, and the present disclosure is not limited to the embodiments and modifications. Various modifications other than the following embodiments and modifications are possible depending on the design, etc., as long as they do not deviate from the technical concept of the present disclosure.

[0010] (Embodiment) A physical quantity measuring system 1 according to this embodiment will be described below with reference to FIGS.

[0011] (1) Overview The physical quantity measuring system 1 of this embodiment is a system that measures at least one of the water vapor pressure of water vapor, which is a specific gas, and the relative humidity of a gas mixture containing multiple gases flowing through a flow path 101 (see FIG. 3). For example, a gas mixture containing hydrogen, nitrogen, and water vapor flows through the flow path 101.

[0012] As shown in FIG. 1 , the physical quantity measurement system 1 of this embodiment includes a temperature and humidity sensor 16, a heat generating unit 17, a heat generation control unit 203, and a water vapor pressure measurement unit 204. The temperature and humidity sensor 16 measures the humidity and temperature of the mixed gas flowing through the flow path 101. The heat generating unit 17 generates heat to warm the temperature and humidity sensor 16. The heat generation control unit 203 controls the heat generating unit 17 to switch its state between an ON state for performing the heat generating operation and an OFF state for stopping the heat generating operation. The heat generation control unit 203 controls the heat generating unit 17 to ON / OFF based on a comparison result between the humidity measurement value of the mixed gas measured by the temperature and humidity sensor 16 and a threshold value. The water vapor pressure measurement unit 204 measures the water vapor pressure of the water vapor contained in the mixed gas. The water vapor pressure measurement unit 204 measures the water vapor pressure of the water vapor based on the humidity measurement value and the temperature measurement value of the mixed gas measured by the temperature and humidity sensor 16, regardless of the state of the heat generating unit 17.

[0013] According to this configuration, even when the mixed gas flows through the flow path in a high-humidity environment, it is possible to reduce the possibility of condensation occurring on the temperature and humidity sensor 16 by controlling the heat generation operation of the heat generating unit 17. As a result, even when the mixed gas flows through the flow path in a high-humidity environment, it is possible to more accurately measure the water vapor pressure of the mixed gas.

[0014] (2) Composition The detailed configuration of the physical quantity measuring system 1 will be described below with reference to FIGS.

[0015] 1, the physical quantity measurement system 1 includes a flow path main body 10 and a processing device 20. The physical quantity measurement system 1 measures the concentration of hydrogen (hydrogen concentration) contained in a mixed gas flowing through the flow path main body 10, the flow rate of the mixed gas, and the relative humidity as physical quantities. Furthermore, the physical quantity measurement system 1 measures the water vapor pressure of water vapor contained in the mixed gas and the concentration of water vapor relative to the mixed gas (water vapor concentration), as physical quantities. Here, the concentration measured by the physical quantity measurement system 1 is, for example, a volume concentration.

[0016] An X-axis, a Y-axis, and a Z-axis are defined for the flow path body 10 (see FIG. 2). The X-axis is an axis along the longitudinal direction of the flow path body 10, i.e., an axis along the direction in which the mixed gas flows. The Y-axis is an axis perpendicular to the X-axis, for example, an axis along the depth direction of the flow path body 10. The Z-axis is an axis perpendicular to both the X-axis and the Y-axis, for example, an axis along the height direction of the flow path body 10. FIG. 3 is a cross-sectional view of the flow path body 10 in the XZ plane. FIG. 4 is a cross-sectional view of the flow path body 10 in the XY plane.

[0017] (2.1) Flow path body A mixed gas flows through the flow path main body 10. As shown in FIG. 1, the flow path main body 10 has a pair of ultrasonic transmitter / receivers 11 and 12, a first temperature sensor 13, a second temperature sensor 14, a pressure sensor 15, a temperature / humidity sensor 16, a heating unit 17, and a switch unit 18. Furthermore, as shown in FIG. 2, the flow path main body 10 further has a main body unit 100. In the following description, the ultrasonic transmitter / receiver 11 may be referred to as the first ultrasonic transmitter / receiver 11, and the ultrasonic transmitter / receiver 12 may be referred to as the second ultrasonic transmitter / receiver 12.

[0018] The main body 100 is formed in a substantially rectangular shape. A flow path 101 is formed in the center of the main body 100, through which a fluid to be measured (mixed gas), such as a mixed gas containing hydrogen, flows (see FIG. 3). A first opening 110 and a second opening 111 are provided at both ends in the longitudinal direction of the main body 100. The first opening 110 and the second opening 111 are provided on both side surfaces of the main body 100 that face each other in the longitudinal direction. The first opening 110 and the second opening 111 are connected by the flow path 101. The mixed gas flows in from the first opening 110, passes through the flow path 101, and flows out from the second opening 111.

[0019] The pair of ultrasonic transmitters and receivers 11, 12 transmit and receive ultrasonic waves. The pair of ultrasonic transmitters and receivers 11, 12 are arranged so that the ultrasonic waves cross the flow of the mixed gas in the flow channel 101. Specifically, the first ultrasonic transmitter and receiver 11 transmits (transmits) ultrasonic waves toward the second ultrasonic transmitter and receiver 12. The first ultrasonic transmitter and receiver 11 receives (receives) ultrasonic waves transmitted from the second ultrasonic transmitter and receiver 12. The second ultrasonic transmitter and receiver 12 transmits (transmits) ultrasonic waves toward the first ultrasonic transmitter and receiver 11. The second ultrasonic transmitter and receiver 12 receives (receives) ultrasonic waves transmitted from the first ultrasonic transmitter and receiver 11. The first ultrasonic transmitter and receiver 11 and the second ultrasonic transmitter and receiver 12 are arranged upstream and downstream at both ends of the shorter side of the flow channel 101 so that the ultrasonic signals cross the flow of the mixed gas. The first ultrasonic transmitter / receiver 11 and the second ultrasonic transmitter / receiver 12 are arranged on opposite sides of the flow channel 101 in the short direction, one upstream and the other downstream, so that ultrasonic signals cross the flow of the mixed gas. Specifically, the first ultrasonic transmitter / receiver 11 is arranged upstream and the second ultrasonic transmitter / receiver 12 is arranged downstream, facing each other (see FIGS. 2 to 4). In the opposing direction between the first ultrasonic transmitter / receiver 11 and the second ultrasonic transmitter / receiver 12, an ultrasonic propagation path 106 that propagates ultrasonic waves is formed (see FIG. 4). The ultrasonic propagation path 106 is inclined at an angle θ with respect to the flow channel 101 (see FIG. 4).

[0020] The pressure sensor 15 is disposed in the center of one of two opposing main surfaces (hereinafter referred to as the upper surface) of the main body 100 in the thickness direction (see FIGS. 2 and 3). The pressure sensor 15 measures the pressure of the mixed gas flowing through the flow path 101.

[0021] The first temperature sensor 13 is disposed on the upper surface on the opposite side of the pressure sensor 15 from the second opening 111 (see FIGS. 2 and 3). That is, the first temperature sensor 13 is disposed upstream of the flow path 101. The first temperature sensor 13 is, for example, a thermocouple, and measures the temperature of the mixed gas flowing through the flow path 101.

[0022] The second temperature sensor 14 is disposed on the upper surface on the opposite side of the pressure sensor 15 from the first opening 110 (see FIGS. 2 and 3). That is, the second temperature sensor 14 is disposed downstream of the flow path 101. The second temperature sensor 14 is, for example, a thermocouple, and measures the temperature of the mixed gas flowing through the flow path 101.

[0023] The temperature and humidity sensor 16 includes a humidity sensor and a temperature sensor. That is, the temperature and humidity sensor 16 measures the humidity and temperature of the mixed gas flowing through the flow path 101. The temperature and humidity sensor 16 is provided on one of two opposing side surfaces of the flow path 101 in the short direction, on which the first ultrasonic transmitter / receiver 11 is provided. The temperature and humidity sensor 16 is arranged downstream of the flow path 101. The first temperature sensor 13 and the second temperature sensor 14 are arranged separately from the temperature and humidity sensor 16 in the flow path 101.

[0024] The heat generating unit 17 is provided in the temperature and humidity sensor 16. The temperature and humidity sensor 16 and the heat generating unit 17 are housed in the same housing 160. The heat generating unit 17 performs a heat generating operation to generate heat that warms the temperature and humidity sensor 16 (particularly the humidity sensor). Because the heat generating unit 17 is provided in the temperature and humidity sensor 16, the influence of the heat generated by the heat generating unit 17 on the second temperature sensor 14 is smaller than the influence on the temperature and humidity sensor 16. In other words, the second temperature sensor 14 measures the temperature of the mixed gas, and is provided in a location where the influence of the heat generated by the heat generating unit 17 is smaller than that on the temperature and humidity sensor 16.

[0025] The switch unit 18 is provided between a power supply unit 26 (see FIG. 1 ), which supplies power to the temperature and humidity sensor 16 and the heat generating unit 17, and a power supply path between the temperature and humidity sensor 16 and the heat generating unit 17. The switch unit 18 is, for example, a metal-oxide-semiconductor field-effect transistor (MOSFET). Under the control of the processing device 20, the power supply path between the power supply unit 26 and the temperature and humidity sensor 16 and the heat generating unit 17 is interrupted, or the power supply path is electrically connected between the power supply unit 26 and the temperature and humidity sensor 16 and the heat generating unit 17. By interrupting the power supply path between the power supply unit 26 and the temperature and humidity sensor 16 and the heat generating unit 17, power is no longer supplied to the temperature and humidity sensor 16 and the heat generating unit 17. This stops the temperature and humidity measurement by the temperature and humidity sensor 16 and prevents the heat generating unit 17 from generating heat. In other words, the switch unit 18 is configured to stop the heat generating operation of the heat generating unit 17 when an abnormality in the heat generating operation of the heat generating unit 17 is detected.

[0026] The flow path main body 10 further has one or more partition plates 107. The one or more partition plates 107 divide the flow path 101 into a plurality of sections at the height H of the flow path 101. By dividing the flow path 101 into a plurality of sections with the one or more partition plates 107, a multilayer flow path 108 is formed in the flow path 101. This configuration increases the aspect ratio of the flow path cross section of each layer of the multilayer flow path 108, making the flow two-dimensional, reducing the Reynolds number, and rectifying the flow and stabilizing turbulence.

[0027] Note that one or more partition plates 107 are not essential components. That is, the flow path main body 10 (physical quantity measuring system 1) does not necessarily have to include the partition plates 107.

[0028] (2.2) Processing equipment As shown in FIG. 1, the processing device 20 includes a first communication unit 21, a second communication unit 22, a third communication unit 23, a fourth communication unit 24, and a control unit 25.

[0029] The processing device 20 includes, for example, a computer system having one or more processors and a memory. The processor executes a program stored in the memory, causing the computer system to function as the control unit 25. The program executed by the processor is pre-recorded in the memory of the computer system here, but may also be provided by being recorded on a non-transitory recording medium such as a memory card, or via a telecommunications line such as the Internet.

[0030] The first communication unit 21 is a communication interface for communicating with the first ultrasonic transmitter / receiver 11 and the second ultrasonic transmitter / receiver 12. The second communication unit 22 is a communication interface for communicating with the first temperature sensor 13, the second temperature sensor 14, the pressure sensor 15, and the temperature / humidity sensor 16. The third communication unit 23 is a communication interface for communicating with the heat generating unit 17 and the switch unit 18. The fourth communication unit 24 is a communication interface for communicating with the user device 30 (see FIG. 2). The user device 30 has a display unit such as a liquid crystal display, and is a device for notifying the user of measurement results, etc., in the physical quantity measurement system 1.

[0031] 1, the control unit 25 has a first signal processing unit 201, a second signal processing unit 202, a heat generation control unit 203, a water vapor pressure measurement unit 204, a concentration measurement unit 205, a flow rate measurement unit 206, and a relative humidity measurement unit 207. Furthermore, the control unit 25 has a first detection unit 208 (environmental abnormality detection unit) and a second detection unit 209 (heat generation abnormality detection unit).

[0032] The first signal processing unit 201 performs processing related to communication between the first ultrasonic transmitter / receiver 11 and the second ultrasonic transmitter / receiver 12 .

[0033] For example, when transmitting ultrasonic waves from the first ultrasonic transmitter / receiver 11 to the second ultrasonic transmitter / receiver 12, the first signal processing unit 201 outputs a signal instructing the first ultrasonic transmitter / receiver 11 to transmit ultrasonic waves to the first ultrasonic transmitter / receiver 11 via the first communication unit 21. When transmitting ultrasonic waves from the second ultrasonic transmitter / receiver 12 to the first ultrasonic transmitter / receiver 11, the first signal processing unit 201 outputs a signal instructing the second ultrasonic transmitter / receiver 12 to transmit ultrasonic waves to the second ultrasonic transmitter / receiver 12 via the first communication unit 21.

[0034] The first signal processing unit 201 also calculates the first propagation time (propagation time of the ultrasonic waves in the forward direction) t up Specifically, the first signal processing unit 201 measures the first propagation time t based on the time when the ultrasonic wave is transmitted from the first ultrasonic transmitter / receiver 11 and the time when the ultrasonic wave transmitted from the first ultrasonic transmitter / receiver 11 is received by the second ultrasonic transmitter / receiver 12. up Measure.

[0035] The first signal processing unit 201 also calculates a second propagation time t of the ultrasonic wave transmitted from the second ultrasonic transmitter / receiver 12 to the first ultrasonic transmitter / receiver 11 (the propagation time of the ultrasonic wave in the reverse direction) dw Specifically, the first signal processing unit 201 measures the second propagation time t based on the time when the ultrasonic wave is transmitted from the second ultrasonic transmitter / receiver 12 and the time when the ultrasonic wave transmitted from the second ultrasonic transmitter / receiver 12 is received by the first ultrasonic transmitter / receiver 11. dw Measure.

[0036] The second signal processing unit 202 receives the signals output from each sensor and performs predetermined processing on the received signals. For example, when the second signal processing unit 202 receives the signal output from the first temperature sensor 13, it performs predetermined signal processing on the received signal to determine the first temperature value measured by the first temperature sensor 13. When the second signal processing unit 202 receives the signal output from the second temperature sensor 14, it performs predetermined signal processing on the received signal to determine the second temperature value measured by the second temperature sensor 14.

[0037] Furthermore, when the second signal processing unit 202 receives the signal output from the pressure sensor 15, it performs predetermined signal processing on the received signal to determine the pressure value measured by the pressure sensor 15.

[0038] When the second signal processing unit 202 receives a signal output from the humidity sensor of the temperature and humidity sensor 16, it performs predetermined signal processing on the received signal to determine the humidity value (measured humidity value) measured by the temperature and humidity sensor 16. When the second signal processing unit 202 receives a signal output from the temperature sensor of the temperature and humidity sensor 16, it performs predetermined signal processing on the received signal to determine the temperature value (measured temperature value) measured by the temperature and humidity sensor 16.

[0039] The heat generation control unit 203 performs on / off control on the heat generation unit 17 to switch the state of the heat generation unit 17 between an on state in which the heat generation operation is performed and an off state in which the heat generation operation is stopped. The heat generation control unit 203 performs on / off control on the heat generation unit 17 based on the result of comparing the humidity measurement value of the mixed gas measured by the temperature and humidity sensor 16 with a first threshold. That is, the heat generation control unit 203 controls the heat generation operation of the heat generation unit 17 according to the result of comparing the humidity measurement value measured by the temperature and humidity sensor 16 with the first threshold. Here, the first threshold is a humidity value at which condensation does not occur on the temperature and humidity sensor 16. For example, the first threshold is set to 70%, which is a humidity value at which condensation does not occur.

[0040] The heat generation control unit 203 turns on the heat generation unit 17 when the humidity measurement value measured by the temperature and humidity sensor 16 is greater than a first threshold (threshold value). The heat generation control unit 203 turns off the heat generation unit 17 when the humidity measurement value measured by the temperature and humidity sensor 16 is equal to or less than the first threshold. Specifically, when the humidity measurement value measured by the temperature and humidity sensor 16 is greater than the first threshold, the heat generation control unit 203 controls the period during which the heat generation unit 17 is in the on state and the period during which the heat generation unit 17 is in the off state by pulse width modulation (PWM), thereby alternately switching between the on state and the off state. The heat generation control unit 203 controls the pulse width of the pulse width modulation so that the on state is longer the greater the difference between the first threshold and the humidity measurement value. Furthermore, the heat generation control unit 203 turns off the heat generation unit 17 when the humidity measurement value is equal to or less than the first threshold. It should be noted that "heat generating unit 17 is in an on state" does not only mean that it is always in an on state, but also means that it is alternately switched between an on state and an off state by control using pulse width modulation.

[0041] The water vapor pressure measuring unit 204 measures the water vapor pressure of the water vapor contained in the mixed gas flowing through the flow path. The water vapor pressure measuring unit 204 measures the water vapor pressure P of the water vapor based on the humidity measurement value, which is the humidity value of the mixed gas measured by the temperature and humidity sensor 16, and the temperature measurement value, which is the temperature value of the mixed gas measured by the temperature and humidity sensor 16, regardless of the state of the heat generating unit 17. W Specifically, the water vapor pressure measuring unit 204 measures the water vapor pressure P W Here, T in Equation 1 is calculated. m is the temperature measurement, and H m is the humidity measurement.

[0042]

number

[0043] Here, the water vapor pressure measuring unit 204 calculates the water vapor pressure using different measurement methods depending on the conditions that are established based on the humidity measurement value. The water vapor pressure measuring unit 204 calculates the water vapor pressure P using either the above equation 1 or the following equation 2 depending on the conditions that are established based on the humidity measurement value.W Here, C in Equation 2 is calculated. W is the correction value for water vapor pressure, and is a value less than or equal to 1.

[0044]

number

[0045] In this embodiment, the water vapor pressure measurement unit 204 measures the water vapor pressure P using either a first measurement method or a second measurement method different from the first measurement method, depending on the condition that is established based on the humidity measurement value. W In the first measurement method, the water vapor pressure P W Calculate the water vapor pressure P using Equation 1. W In the second measurement method, the water vapor pressure P is calculated using the temperature measurement value, the humidity measurement value, and a correction value according to the first threshold value. W Calculate the water vapor pressure P using Equation 2. W Calculate.

[0046] When using Equation 1, if the humidity measurement value is greater than the first threshold value, the water vapor pressure measurement unit 204 calculates the water vapor pressure P W In other words, when the water vapor pressure measurement unit 204 uses Equation 1, if the humidity measurement value is greater than the first threshold, the water vapor pressure measurement unit 204 uses Equation 2 to calculate the water vapor pressure P W When the water vapor pressure measurement unit 204 uses Equation 1, if the humidity measurement value is equal to or less than the first threshold value, the water vapor pressure P W In other words, when the water vapor pressure measurement unit 204 uses Equation 1 and the humidity measurement value is equal to or less than the first threshold value, the water vapor pressure measurement unit 204 does not change the formula used to calculate the water vapor pressure P W In this embodiment, when using Equation 2, if the humidity measurement value is greater than the second threshold value, the water vapor pressure measurement unit 204 calculates the water vapor pressure P W In other words, when the water vapor pressure measurement unit 204 uses Equation 2 and the humidity measurement value is greater than the second threshold value, the water vapor pressure measurement unit 204 does not change the equation used to calculate the water vapor pressure P WWhen using Equation 2, if the humidity measurement value falls below the second threshold, the water vapor pressure measurement unit 204 calculates the water vapor pressure P W In other words, when using Equation 2, if the humidity measurement value falls below the second threshold, the water vapor pressure measurement unit 204 uses Equation 1 to calculate the water vapor pressure P W Here, the second threshold is a value smaller than the first threshold. For example, if the first threshold is set to 70% as the humidity value at which condensation does not occur, the second threshold is set to 60%.

[0047] That is, the water vapor pressure measurement unit 204 calculates the water vapor pressure P W In the first state, the water vapor pressure P is calculated using Equation 2. W Hereinafter, the measurement method using Equation 1 will be referred to as the first measurement method, and the measurement method using Equation 2 will be referred to as the second measurement method.

[0048] When the measurement state is a first state in which measurement is performed using a first measurement method, the water vapor pressure measurement unit 204 switches the measurement state from the first state to a second state in which measurement is performed using a second measurement method if the humidity measurement value is greater than a first threshold, and maintains the measurement state in the first state if the humidity measurement value is equal to or less than the first threshold. In other words, when the measurement state is the first state, the water vapor pressure measurement unit 204 switches the measurement method from the first measurement method to the second measurement method if the humidity measurement value is greater than the first threshold, and maintains the measurement method as the first measurement method if the humidity measurement value is equal to or less than the first threshold.

[0049] When the measurement state is the second state, the water vapor pressure measurement unit 204 switches the measurement state from the second state to the first state if the measured humidity value falls below a second threshold value that is smaller than the first threshold value, and maintains the measurement state in the second state if the measured humidity value is greater than the second threshold value. In other words, when the measurement state is the second state, the water vapor pressure measurement unit 204 switches the measurement method from the second measurement method to the first measurement method if the measured humidity value falls below the second threshold value, and maintains the measurement method in the second measurement method if the measured humidity value is greater than the second threshold value.

[0050] The concentration measurement unit 205 measures the water vapor pressure measured by the water vapor pressure measurement unit 204 and the pressure P of the mixed gas measured by the pressure sensor 15. m The water vapor concentration x is the concentration of water vapor contained in the gas mixture based on w Specifically, the concentration measurement unit 205 measures the water vapor concentration x using the following equation 3: w Ask for.

[0051]

number

[0052] Furthermore, the concentration measurement unit 205 measures the gas concentration, which is the concentration of a gas that is contained in the mixed gas and is different from water vapor, based on the determined water vapor concentration and the propagation time of the ultrasonic waves in the pair of ultrasonic transmitter-receivers (the first ultrasonic transmitter-receiver 11 and the second ultrasonic transmitter-receiver 12). For example, the concentration measurement unit 205 measures the gas concentration, which is the concentration of a gas that is contained in the mixed gas and is different from water vapor, based on the determined water vapor concentration x w The concentration of hydrogen contained in the mixed gas (hydrogen concentration) is measured based on the propagation time of the ultrasonic waves. Here, the sound speed c of the mixed gas, the molecular weight M of the mixed gas, and the specific heat ratio γ (= c p / c v ), the temperature T of the mixed gas, and the gas constant R, the relationship shown in Equation 4 holds true. p is the constant pressure molar specific heat. v is the molar specific heat at constant volume.

[0053]

number

[0054] Here, the distance between the ultrasonic sensors (the length of the ultrasonic propagation path 106) is set to L. In this case, the speed of sound c is calculated by multiplying the distance L by the measured first propagation time t up and the second propagation time t dw The mean propagation time t ave and the relation shown in Equation 5 holds.

[0055]

number

[0056] In this embodiment, the mixed gas contains hydrogen, nitrogen, and water vapor. Here, the molecular weight of hydrogen is M1, and the specific heat at constant pressure is c p1 , specific heat at constant volume is c v1 The molecular weight of nitrogen is M2, and the specific heat at constant pressure is c p2 , specific heat at constant volume is c v2 The molecular weight of water vapor is M w , specific heat at constant pressure is c pw , specific heat at constant volume is c vw Furthermore, let the concentration of hydrogen be x1. In this case, the following equations 6 to 8 hold true.

[0057]

number

[0058]

number

[0059]

number

[0060] Using equations 6 to 8, and temperature T is the temperature measurement value T m Then, we can transform number 4 into number 9.

[0061]

number

[0062] The concentration measurement unit 205 calculates the hydrogen concentration x1 using Equation 9.

[0063] In addition, in Equation 5 and Equation 9, the average measured hydrogen propagation time is t ave1 , temperature is T m1 , x1=1, x w = 0, the actual distance L (= L1) between the ultrasonic sensors can be calculated. This allows for highly accurate measurement of hydrogen concentration.

[0064] Furthermore, in Equation 5 and Equation 9, the average of the measured propagation time of nitrogen is t ave2 , temperature is T m2 , x1=0, x w = 0, the actual distance L (= L2) between the ultrasonic sensors can be calculated.

[0065] Ideally, L1 = L2, but differences between L2 and L1 may occur due to the difference between the theoretical value and the actual measurement, or due to the influence of fixed errors that occur when converting propagation times. In this case, the average propagation time t ave The difference time t d The corrected propagation time (t ave -t d ) is used to define the speed of sound as follows:

[0066]

number

[0067] Using equation 10, t where L1 = L2 d and L can be determined. d and L is the value of t under the condition that L1 = L2. d It may be calculated numerically using =0 as the initial value, or it may be calculated algebraically from the following equations 11 and 12.

[0068]

number

[0069]

number

[0070] The obtained t d , L in the calculations of Equations 9 and 10, the concentration measurement unit 205 can perform concentration measurement with higher accuracy.

[0071] The flow rate measuring unit 206 measures the flow rate of the mixed gas in the flow path 101 using the ultrasonic wave propagation time, water vapor concentration, and gas concentrations (hydrogen concentration, nitrogen concentration). The flow rate measuring unit 206 calculates the flow rate Q of the mixed gas using the following equations 13 and 14. Equation 13 is a formula for calculating the tentative flow rate Q0. The tentative flow rate Q0 is calculated by multiplying the cross-sectional area S of the flow path 101 by the flow velocity V. In addition, the flow velocity V, the length L of the ultrasonic propagation path 106 (the distance between the first ultrasonic transmitter / receiver 11 and the second ultrasonic transmitter / receiver 12), the first propagation time t up , the second propagation time t dw From the relationship between the angle θ of the ultrasonic wave propagation path 106 and the flow path 101, "Q0=SV" can be transformed into the right side of Equation 13. Here, R K is the flow coefficient.

[0072]

number

[0073]

number

[0074] In addition, the flow coefficient R K is the kinematic viscosity ν, characteristic length D, and flow velocity V m is defined by the following equation 15, where R e is the Reynolds number. That is, the Reynolds number R e is the formula "R e =V mThe characteristic length D is expressed as D / ν”. The characteristic length D is, for example, the length between the partition plates 107, or the length between one of the two side walls that face each other in the height H direction and form the flow path 101 and the partition plate 107 that is closest to the one side wall. When the partition plate 107 is not provided, the characteristic length D is, for example, the height H. In addition, the function f(R e ) is a predetermined function. m is the flow velocity corresponding to the flow rate measured by the standard device during calibration (hereinafter referred to as the reference flow rate) performed as a preliminary evaluation.

[0075]

number

[0076] Here, the kinematic viscosity ν is determined by the temperature T in the flow path 101, the concentration of each gas (hydrogen, nitrogen, water vapor) contained in the mixed gas, and the pressure P m The dynamic viscosity ν is a value that depends on the equation "dynamic viscosity = viscosity / density", so it can be obtained from the following equation 16. The transformation from the middle side to the right side in equation 16 is based on the gas state equation "pressure P m From equation 1, "density = mass / volume," we can obtain equation 2, "density = (molecular weight M) · pressure P": m ) / (gas constant R·temperature T). In other words, from the gas equation of state and relation 1, density ρ can be calculated by the molecular weight M and pressure P m , temperature T and gas constant R. Here, pressure P m is the pressure measured by the pressure sensor 15. The temperature T is the average value of the first temperature value measured by the first temperature sensor 13 and the second temperature value measured by the second temperature sensor 14. The density ρ is determined by the concentration, temperature, and pressure of the gas. Therefore, in Relational Formula 2, the molecular weight M is a function (see Equation 6) with the concentration as a variable.

[0077]

number

[0078] μ(x, T) in Equation 16 can be calculated from the viscosity of each gas (hydrogen, nitrogen, water vapor) contained in the mixed gas. The viscosity of each gas can be calculated by a known method. The viscosity μ of the mixed gas can be calculated using the viscosity of each gas calculated by a known method and the concentration of each gas (hydrogen concentration, nitrogen concentration, water vapor concentration) that has already been calculated.

[0079] The flow rate measurement unit 206 calculates the standard flow rate Q of the mixed gas converted to 0°C and 1 atm based on the calculated flow rate Q of the mixed gas. n Ask for.

[0080] The flow rate measurement unit 206 measures the flow rate of the gas using the flow rate of the mixed gas. Specifically, the flow rate measurement unit 206 measures the standard flow rate Q calculated based on the flow rate Q of the mixed gas. n The flow rate measurement unit 206 measures the gas flow rate by multiplying the standard flow rate Q n The flow rate measurement unit 206 may obtain the flow rate of hydrogen by multiplying the flow rate Q by the hydrogen concentration x1 as a gas concentration.

[0081] where, the flow coefficient R K We will explain how to calculate this.

[0082] Flow coefficient R K is the virtual flow rate Q0 and the reference flow rate Q m Using the above, it is expressed as the following equation 17. Here, the reference flow rate Q m is the flow rate measured by the standard device at the time of calibration.

[0083]

number

[0084] Also, the Reynolds number R e is the reference flow rate Q m Using the above equation, it is expressed by the following equation 18. In equation 18, ν represents the kinematic viscosity of the mixed gas, D represents the characteristic length, and S represents the cross-sectional area of ​​the flow path 101. V m is the reference flow rate Q measured by the standard device during calibration mis the flow velocity corresponding to

[0085]

number

[0086] The processing device 20 calculates the reference flow rate Q using Equations 17 and 18. m When the Reynolds number R is changed e and the flow coefficient R calculated using the provisional flow rate Q0 obtained from the measurement value. K Multiple combinations of (R e , R K ) is calculated as a preliminary evaluation, and the Reynolds number R e and the flow coefficient R K The relational expression is calculated and stored in advance.

[0087] Furthermore, using equations 17 and 18, the Reynolds number R e and the flow coefficient R K The characteristic length D and cross-sectional area S are known values ​​in the physical quantity measurement system 1, and the kinematic viscosity ν and provisional flow rate Q0 are values ​​that have already been calculated. That is, the flow coefficient R K is the Reynolds number R e In other words, Equation 19 is expressed as a linear function using the Reynolds number R e and the flow coefficient R K and the coefficient is a value ((νS) / (Q0D)) based on the tentative flow rate Q0 and the kinematic viscosity ν of the mixed gas.

[0088]

number

[0089] The flow rate measurement unit 206 measures the Reynolds number R obtained by a pre-evaluation. e and the flow coefficient R K Using the relational expression that expresses the relationship between KSpecifically, the flow rate measurement unit 206 calculates the flow rate coefficient R corresponding to the provisional flow rate Q0 by finding the intersection between the graph represented by the relational expression obtained by the pre-evaluation and the graph represented by Equation 19. K Calculate.

[0090] The flow rate measurement unit 206 calculates the flow rate coefficient R K and calculate the flow rate Q using equation 14.

[0091] Here, the kinematic viscosity ν appears in both Equation 15 and Equation 18. That is, the flow coefficient R K is a value based on the kinematic viscosity ν of the mixed gas. Also, according to equation 18, the Reynolds number R e The coefficient is the dynamic viscosity ν. In other words, the flow coefficient R K is a value obtained by using a linear function of the Reynolds number, with a coefficient based on the kinematic viscosity ν of the mixed gas. More specifically, the flow coefficient R K is a value obtained from a linear function of the Reynolds number, whose coefficient is a value based on the kinematic viscosity ν of the mixed gas, and a relational expression that expresses the relationship between the Reynolds number obtained by a pre-evaluation and the flow coefficient.

[0092] The processing device 20 uses the Reynolds number R calculated by the pre-evaluation instead of using the relational expression by the pre-evaluation. e and the flow coefficient R K Multiple combinations with (R e , R K ) may be used.

[0093] The relative humidity measuring unit 207 measures the water vapor pressure P W and the saturated water vapor pressure P according to the temperature (temperature of the mixed gas) measured by the second temperature sensor 14. WS More specifically, the relative humidity measurement unit 207 measures the relative humidity of the mixed gas based on the humidity measurement value H measured by the temperature and humidity sensor 16. m and the temperature measurement value T m, and the temperature of the mixed gas (second temperature value) measured by the second temperature sensor 14, the relative humidity measurement unit 207 calculates the relative humidity of the mixed gas using the following equation 20 or 21. When the measurement state is the first state, the relative humidity measurement unit 207 calculates the relative humidity of the mixed gas using equation 20. When the measurement state is the second state, the relative humidity measurement unit 207 calculates the relative humidity of the mixed gas using equation 21. Here, P WS is the saturated water vapor pressure at the temperature measured by the second temperature sensor 14. That is, P WS is the saturated vapor pressure of the gas mixture at the temperature. n is the temperature measured by the second temperature sensor 14 (second temperature value).

[0094]

number

[0095]

number

[0096] When the measurement state is the first state, the relative humidity measurement unit 207 calculates the humidity measurement value H m may be taken as the relative humidity H0 of the gas mixture.

[0097] The first detection unit 208 detects an abnormality in the measurement environment of the temperature and humidity sensor 16 when the heating unit 17 is in the ON state. That is, the first detection unit 208 functions as an environmental abnormality detection unit that detects an abnormality in the measurement environment of the temperature and humidity sensor 16 when the heating unit 17 is in the ON state. The first detection unit 208 calculates the standard deviation σ of the humidity measurement values ​​based on the humidity measurement values ​​measured by the temperature and humidity sensor 16 when the heating unit 17 is in the ON state. Here, the standard deviation σ calculated by the first detection unit 208 is the standard deviation for a predetermined period when the heating unit 17 is in the ON state. The first detection unit 208 calculates the water vapor pressure P WFor example, the first detection unit 208 determines a reference value according to the water vapor pressure P measured by the water vapor pressure measurement unit 204 from among the predetermined values ​​corresponding to the plurality of water vapor pressures stored in advance in the memory. W The first detection unit 208 acquires (determines) a predetermined value according to the standard deviation σ as a reference value. If the standard deviation σ is greater than the reference value, the first detection unit 208 detects that an abnormality has occurred when the heat generating unit 17 is in the on state. Here, in this embodiment, the first detection unit 208 detects that the temperature and humidity sensor 16 is submerged in water as an abnormality in the measurement environment of the temperature and humidity sensor 16.

[0098] When the first detection unit 208 detects that an abnormality has occurred while the heat generating unit 17 is in the on state, it outputs a first detection result indicating that an abnormality has occurred in the measurement environment of the temperature and humidity sensor 16 to the user device 30 via the fourth communication unit 24.

[0099] The second detection unit 209 detects an abnormality in the heat generation operation by the heat generating unit 17. That is, the second detection unit 209 functions as a heat generation abnormality detection unit that detects an abnormality in the heat generation operation. The second detection unit 209 detects that an abnormality has occurred when the heat generation operation by the heat generating unit 17 is being performed and the humidity measurement value of the mixed gas and the temperature measurement value of the mixed gas measured by the temperature and humidity sensor 16 satisfy predetermined conditions. That is, the second detection unit 209 detects that an abnormality has occurred when the humidity measurement value of the mixed gas and the temperature measurement value of the mixed gas measured by the temperature and humidity sensor 16 during the heat generation operation by the heat generating unit 17 satisfy predetermined conditions. Specifically, the second detection unit 209 detects that an abnormality has occurred in the heat generation operation, as it has satisfied the specified conditions, when the result (first difference value) of subtracting the humidity measurement value from the first threshold value is greater than the first comparison value, the result (second difference value) of subtracting the temperature measured by the second temperature sensor 14 (second temperature value) from the temperature measurement value is greater than the second comparison value, and the temperature measurement value is greater than a predetermined third comparison value.

[0100] Here, the abnormality detected by the second detection unit 209 is a communication error related to communication of a signal for stopping the heat generation operation of the heat generation unit 17. Alternatively, the abnormality detected by the second detection unit 209 is a malfunction inside the physical quantity measurement system 1. The malfunction inside the physical quantity measurement system 1 is, for example, a breakdown of the heat generation unit 17.

[0101] When the second detection unit 209 detects that an abnormality has occurred, it outputs a second detection result indicating that an abnormality has occurred in the heat-generating operation to the user device 30 via the fourth communication unit 24.

[0102] When the second detection unit 209 detects that an abnormality has occurred in the heat generation operation, it outputs a cut-off instruction signal to the switch unit 18 via the third communication unit 23, instructing the switch unit 18 to cut off the power supply path between the power supply unit 26 and the temperature / humidity sensor 16 and the heat generation unit 17. When the switch unit 18 receives the cut-off instruction signal, it cuts off the power supply path between the power supply unit 26 and the temperature / humidity sensor 16 and the heat generation unit 17. This stops the heat generation operation of the heat generation unit 17.

[0103] In addition, the second detection unit 209 may detect that an abnormality has occurred in the heat generation operation by determining that a predetermined condition is met when the result (first difference value) of subtracting the humidity measurement value from the first threshold value is greater than the first comparison value and the result (second difference value) of subtracting the temperature measured by the second temperature sensor 14 (second temperature value) from the temperature measurement value is greater than the second comparison value.

[0104] (3) Operation Here, the operation of the physical quantity measuring system 1 will be described.

[0105] (3.1) Operation overview Here, an outline of the operation of the physical quantity measuring system 1 will be described with reference to FIG.

[0106] The first signal processing unit 201 performs a first measurement process (step S1). Specifically, the first signal processing unit 201 measures a first propagation time t upThe first signal processing unit 201 also measures the second propagation time t dw Measure.

[0107] The second signal processing unit 202 performs a second measurement process (step S2). Specifically, the second signal processing unit 202 determines a first temperature value measured by the first temperature sensor 13 based on the signal output from the first temperature sensor 13. The second signal processing unit 202 determines a second temperature value measured by the second temperature sensor 14 based on the signal output from the second temperature sensor 14. The second signal processing unit 202 also determines a pressure value measured by the pressure sensor 15 based on the signal output from the pressure sensor 15. The second signal processing unit 202 determines a humidity value measured by the temperature and humidity sensor 16 (humidity measurement value) and a temperature value measured by the temperature and humidity sensor 16 (temperature measurement value) based on the signal output from the humidity sensor of the temperature and humidity sensor 16.

[0108] The heat generation control unit 203 performs heat generation control processing (step S3). The heat generation control unit 203 performs on / off control on the heat generation unit 17 to switch the state of the heat generation unit 17 between an on state in which the heat generation operation is performed and an off state in which the heat generation operation is stopped.

[0109] The water vapor pressure measuring unit 204 performs a third measurement process (step S4). The water vapor pressure measuring unit 204 executes the third measurement process to calculate the water vapor pressure and the water vapor concentration.

[0110] The first detection unit 208 performs a first abnormality detection process (step S5). The first detection unit 208 executes the first abnormality detection process to detect an abnormality in the measurement environment of the temperature and humidity sensor 16.

[0111] The second detection unit 209 performs a second abnormality detection process (step S6). The second detection unit 209 executes the second abnormality detection process to detect an abnormality in the heat generation operation of the heat generating unit 17.

[0112] The concentration measurement unit 205 performs the concentration measurement process to calculate the concentration of hydrogen flowing through the flow path 101 (step S7).

[0113] The flow rate measurement unit 206 performs a flow rate measurement process (step S8). The flow rate measurement unit 206 executes the flow rate measurement process to calculate the flow rate of the mixed gas flowing through the flow path 101 and the flow rate of hydrogen contained in the mixed gas.

[0114] The relative humidity measurement unit 207 performs a relative humidity measurement process (step S9). The relative humidity measurement unit 207 executes the relative humidity measurement process and calculates the relative humidity of the mixed gas flowing through the flow path 101.

[0115] The processing device 20 (controller 25 thereof) notifies the user device 30 via the fourth communication unit 24 of at least one of the calculated flow rate, concentration, and relative humidity of the mixed gas.

[0116] (3.2) Heat control processing Here, the heat generation control process shown in step S3 of FIG. 5 will be described with reference to FIG.

[0117] The heat generation control unit 203 acquires the humidity measurement value obtained by the second signal processing unit 202 (step S51).

[0118] The heat generation control unit 203 determines whether the acquired humidity measurement value is greater than the first threshold value (step S52).

[0119] If it is determined that the measured humidity value is greater than the first threshold value ("Yes" in step S52), the heat generation control unit 203 sets the operating state of the heat generation unit 17 to the ON state (step S53). Specifically, when the measured humidity value is greater than the first threshold value, the heat generation control unit 203 controls the period during which the heat generation unit 17 is in the ON state and the period during which the heat generation unit 17 is in the OFF state by pulse width modulation, thereby alternately switching between the ON state and the OFF state. The heat generation control unit 203 controls the pulse width in the pulse width modulation so that the ON state becomes longer as the difference between the first threshold value and the measured humidity value increases.

[0120] If it is determined that the measured humidity value is not greater than the first threshold value, that is, that the measured humidity value is equal to or less than the first threshold value ("No" in step S52), the heat generation control unit 203 turns the heat generation unit 17 off.

[0121] (3.3) Third measurement process Here, the third measurement process shown in step S4 of FIG. 5 will be described with reference to FIG.

[0122] The water vapor pressure measuring unit 204 determines whether the measurement state is the first state (step S101).

[0123] When it is determined that the measurement state is the first state ("Yes" in step S101), the water vapor pressure measurement unit 204 determines whether the humidity measurement value obtained by the second signal processing unit 202 is greater than a first threshold value (step S102).

[0124] When it is determined that the humidity measurement value is not greater than the first threshold, i.e., the humidity measurement value is equal to or less than the first threshold ("No" in step S102), the water vapor pressure measurement unit 204 sets the measurement state to the first state (step S103). After setting the measurement state to the first state in step S103, the water vapor pressure measurement unit 204 performs a first water vapor pressure calculation process (step S104). Specifically, the water vapor pressure measurement unit 204 calculates the water vapor pressure P W After that, the concentration measurement unit 205 performs a first water vapor concentration calculation process (step S105). The concentration measurement unit 205 calculates the water vapor pressure P W and the pressure P of the mixed gas obtained by the second signal processing unit 202 m Using the above equation (3), the water vapor concentration x of the water vapor contained in the mixed gas is w Measure.

[0125] If it is determined that the measurement state is not the first state, i.e., that the measurement state is the second state ("No" in step S101), the water vapor pressure measuring unit 204 determines whether the humidity measurement value obtained by the second signal processing unit 202 is greater than a second threshold value (step S106).

[0126] If it is determined that the humidity measurement value is greater than the second threshold value ("Yes" in step S106), the water vapor pressure measurement unit 204 sets the measurement state to the second state (step S107). After setting the measurement state to the second state in step S107, the water vapor pressure measurement unit 204 performs a second water vapor pressure calculation process (step S108). Specifically, the water vapor pressure measurement unit 204 calculates the water vapor pressure P W Thereafter, the concentration measurement unit 205 performs a second water vapor concentration calculation process (step S109). The concentration measurement unit 205 calculates the water vapor pressure P W and the pressure P of the mixed gas obtained by the second signal processing unit 202 m Using the above equation (3), the water vapor concentration x of the water vapor contained in the mixed gas is w Measure.

[0127] If it is determined in step S102 that the humidity measurement value is greater than the first threshold value ("Yes" in step S102), the water vapor pressure measurement unit 204 sets the measurement state to the second state (step S107). After setting the measurement state to the second state in step S107, the water vapor pressure measurement unit 204 performs a second water vapor pressure calculation process (step S108). Thereafter, the concentration measurement unit 205 performs a second water vapor concentration calculation process (step S109).

[0128] If it is determined in step S106 that the humidity measurement value is not greater than the second threshold, i.e., that the humidity measurement value is equal to or less than the second threshold ("No" in step S106), the water vapor pressure measurement unit 204 sets the measurement state to the first state (step S103). After setting the measurement state to the first state in step S103, the water vapor pressure measurement unit 204 performs a first water vapor pressure calculation process (step S104). Thereafter, the concentration measurement unit 205 performs a first water vapor concentration calculation process (step S105).

[0129] (3.4) First abnormality detection process Here, the first abnormality detection process shown in step S5 of FIG. 5 will be described with reference to FIG.

[0130] When the heating unit 17 is in the on state, the first detection unit 208 calculates the standard deviation σ of the humidity measurement values ​​based on the humidity measurement values ​​measured by the temperature and humidity sensor 16 (step S151).

[0131] The first detection unit 208 detects the water vapor pressure P measured by the water vapor pressure measurement unit 204. W For example, the first detection unit 208 determines a reference value according to the water vapor pressure P measured by the water vapor pressure measurement unit 204 among the predetermined values ​​corresponding to each of the plurality of water vapor pressures (step S152). W A predetermined value according to the above is acquired (determined) as a reference value.

[0132] The first detection unit 208 determines whether the standard deviation σ is greater than the reference value (step S153).

[0133] If the first detection unit 208 determines that the standard deviation σ is not greater than the reference value ("No" in step S153), the process ends. If the first detection unit 208 determines that the standard deviation σ is greater than the reference value ("Yes" in step S153), the first detection unit 208 detects that an abnormality has occurred in the measurement environment of the temperature and humidity sensor 16 when the heating unit 17 is in the on state, for example, that the temperature and humidity sensor 16 is submerged in water as an abnormality in the measurement environment of the temperature and humidity sensor 16 (step S154).

[0134] When the first detection unit 208 detects that an abnormality has occurred in the measurement environment of the temperature and humidity sensor 16 while the heat generation unit 17 is in the on state, it outputs a first detection result indicating that an abnormality has occurred in the measurement environment of the temperature and humidity sensor 16 to the user device 30 (step S155).

[0135] (3.5) Second anomaly detection process Here, the second abnormality detection process shown in step S6 of FIG. 5 will be described with reference to FIG.

[0136] The second detection unit 209 determines whether the result (first difference value) of subtracting the humidity measurement value from the first threshold value is greater than the first comparison value (step S201).

[0137] If the second detection unit 209 determines that the first difference value is not greater than the first comparison value ("No" in step S201), the process ends. If the second detection unit 209 determines that the first difference value is greater than the first comparison value ("Yes" in step S201), the second detection unit 209 determines whether the result (second difference value) obtained by subtracting the temperature measured by the second temperature sensor 14 (second temperature value) from the temperature measurement value is greater than the second comparison value (step S202).

[0138] If the second detection unit 209 determines that the second difference value is not greater than the second comparison value ("No" in step S202), the process ends. If the second detection unit 209 determines that the second difference value is greater than the second comparison value ("Yes" in step S202), the second detection unit 209 determines whether the temperature measurement value is greater than a third comparison value (step S203).

[0139] If the second detection unit 209 determines that the temperature measurement value is not greater than the third comparison value ("No" in step S203), the process ends. If the second detection unit 209 determines that the temperature measurement value is greater than the third comparison value ("Yes" in step S203), the second detection unit 209 determines that a predetermined condition is met and detects that an abnormality has occurred in the heat generation operation (step S204).

[0140] When second detection unit 209 detects that an abnormality has occurred in the heat-generating operation, second detection unit 209 outputs a second detection result indicating that an abnormality has occurred in the heat-generating operation to user device 30 (step S205).

[0141] When the second detection unit 209 detects that an abnormality has occurred in the heat generation operation, it performs a cut-off process (step S206). The second detection unit 209 outputs a cut-off instruction signal to the switch unit 18 via the third communication unit 23. Upon receiving the cut-off instruction signal, the switch unit 18 cuts off the power supply path between the power supply unit 26 and the temperature and humidity sensor 16 and the heat generation unit 17. This stops the heat generation operation of the heat generation unit 17.

[0142] (3.6) Concentration measurement processing Here, the concentration measurement process shown in step S7 of FIG. 5 will be described with reference to FIG.

[0143] The concentration measurement unit 205 executes a concentration measurement process to measure the gas concentration, which is the concentration of a gas (here, hydrogen) that is contained in the mixed gas and that is different from water vapor.

[0144] The concentration measurement unit 205 performs a sound speed calculation process (step S251). The concentration measurement unit 205 calculates the sound speed based on the propagation time of the ultrasonic waves.

[0145] The concentration measurement unit 205 performs a hydrogen concentration calculation process (step S252). The concentration measurement unit 205 calculates the water vapor concentration x calculated in the first water vapor concentration calculation process or the second water vapor concentration calculation process of the third measurement process. w and the speed of sound are used to calculate the concentration of hydrogen.

[0146] (3.7) Sound speed calculation process Here, the sound speed calculation process shown in step S251 of FIG. 10 will be described with reference to FIG.

[0147] The concentration measurement unit 205 calculates the concentration based on the pre-stored distance L (the distance between the first ultrasonic transmitter / receiver 11 and the second ultrasonic transmitter / receiver 12) and the first propagation time t measured by the first signal processing unit 201. up and the second propagation time t dw and are acquired (step S261).

[0148] The concentration measurement unit 205 measures the first propagation time t up and the second propagation time tdw and the average propagation time t ave is calculated (step S262).

[0149] The concentration measurement unit 205 calculates the distance L acquired in step S261 and the average propagation time t ave The sound speed is calculated using the above-mentioned equation 5 (step S263).

[0150] (3.8) Hydrogen concentration calculation process Here, the hydrogen concentration calculation process shown in step S252 of FIG. 10 will be described with reference to FIG.

[0151] The concentration measurement unit 205 measures the temperature measurement value T m is acquired (step S271).

[0152] The concentration measurement unit 205 measures the sound velocity c calculated in the sound velocity process and the water vapor concentration x calculated in the third measurement process. w is acquired (step S272).

[0153] The concentration measurement unit 205 acquires each parameter stored in advance (step S273). The concentration measurement unit 205 acquires the gas constant R, the molecular weight M1 of hydrogen, the molecular weight M2 of nitrogen, the molecular weight M W The constant pressure specific heat of each gas (hydrogen, nitrogen, water vapor) and the constant volume specific heat of each gas (hydrogen, nitrogen, water vapor) are obtained as parameters.

[0154] The concentration measurement unit 205 calculates the hydrogen concentration x1 (step S274). m , gas constant R, water vapor concentration x w , molecular weight of hydrogen M1, molecular weight of nitrogen M2, molecular weight of water vapor M W , the specific heat at constant pressure of each gas (hydrogen, nitrogen, water vapor), the specific heat at constant volume of each gas (hydrogen, nitrogen, water vapor) and Equation 9 are used to calculate the hydrogen concentration x1. That is, the concentration measurement unit 205 calculates the hydrogen concentration x1 using the sound speed c, the temperature measurement value T m , gas constant R, molecular weight of the mixture gas M, specific heat ratio of the mixture gas γ(=cp / c v ) and Equation 4 to calculate the hydrogen concentration x1.

[0155] (3.9) Flow measurement processing Here, the flow rate measurement process shown in step S8 of FIG. 5 will be described with reference to FIG.

[0156] The flow rate measurement unit 206 calculates the first propagation time t up and the second propagation time t dw and are acquired (step S301).

[0157] The flow rate measurement unit 206 acquires each parameter stored in advance (step S302). The flow rate measurement unit 206 acquires the cross-sectional area S of the flow path 101, the length L of the ultrasonic propagation path 106 (the distance L between the first ultrasonic transmitter / receiver 11 and the second ultrasonic transmitter / receiver 12), and the angle θ at which the ultrasonic propagation path 106 is inclined with respect to the flow path 101 as the parameters.

[0158] The flow rate measurement unit 206 performs a tentative flow rate calculation process (step S303). Specifically, the flow rate measurement unit 206 calculates the first propagation time t up and the second propagation time t dw A tentative flow rate Q0 is calculated using the cross-sectional area S, length L, and angle θ obtained in step S302 and equation (13) (step S303).

[0159] The flow rate measurement unit 206 performs a flow rate coefficient calculation process (step S304). By performing the flow rate coefficient calculation process, the flow rate measurement unit 206 calculates the flow rate coefficient R K Calculate.

[0160] The flow rate measurement unit 206 calculates the tentative flow rate Q0 and the flow rate coefficient R K and Equation 14 to calculate the flow rate Q (step S305).

[0161] The flow rate measurement unit 206 calculates the standard flow rate Q of the mixed gas converted to 0°C and 1 atm based on the calculated flow rate Q. nis calculated (step S306).

[0162] The flow rate measurement unit 206 acquires the hydrogen concentration x1 calculated in step S274 and calculates the standard flow rate Q n The flow rate measurement unit 206 may multiply the calculated flow rate Q by the hydrogen concentration x1 as a gas concentration to obtain the flow rate of hydrogen (step S307).

[0163] (3.10) Flow coefficient calculation process Here, the flow coefficient calculation process shown in step S304 of FIG. 13 will be described with reference to FIG.

[0164] The flow rate measurement unit 206 measures the temperature T and the pressure P m The temperature T is the average value of the first temperature value measured by the first temperature sensor 13 and the second temperature value measured by the second temperature sensor 14 (step S351).

[0165] The flow rate measurement unit 206 acquires the concentrations of water vapor, hydrogen, and nitrogen contained in the mixed gas (step S352). That is, the flow rate measurement unit 206 acquires the hydrogen concentration x1, the nitrogen concentration x2, and the water vapor concentration x w (=x3) where the nitrogen concentration x2 is 1-x1-x w It is expressed as:

[0166] The flow rate measurement unit 206 acquires each parameter stored in advance (step S353). The flow rate measurement unit 206 acquires the characteristic length D and the cross-sectional area S of the flow path 101 as parameters. Furthermore, the flow rate measurement unit 206 acquires the viscosity of each gas (hydrogen, nitrogen, water vapor) contained in the mixed gas.

[0167] The flow rate measurement unit 206 measures the viscosity of each of hydrogen, nitrogen, and water vapor, and the water vapor concentration x w Using the hydrogen concentration x1 and the nitrogen concentration x2, the viscosity μ of the mixed gas containing hydrogen, nitrogen, and water vapor is calculated (step S354).

[0168] The flow rate measurement unit 206 measures the water vapor concentration x w Using the hydrogen concentration x1, the nitrogen concentration x2, and Equation 16, the kinematic viscosity ν of the mixed gas containing hydrogen, nitrogen, and water vapor is calculated (step S355).

[0169] The flow rate measurement unit 206 obtains the intersection of the graph expressed by the relational expression obtained by the preliminary evaluation and the graph expressed by Equation 19, thereby obtaining the flow rate coefficient R corresponding to the provisional flow rate Q0. K is calculated (step S356).

[0170] (3.11) Relative humidity measurement processing Here, the relative humidity measurement process shown in step S9 of FIG. 5 will be described with reference to FIG.

[0171] The relative humidity measurement unit 207 determines whether the measurement state is the first state (step S401).

[0172] When it is determined that the measurement state is the first state ("Yes" in step S401), the relative humidity measurement unit 207 performs a first humidity measurement process (step S402). Specifically, the relative humidity measurement unit 207 measures the water vapor pressure P W , the saturated water vapor pressure P WS and calculate the relative humidity of the gas mixture using equation (20) above.

[0173] When it is determined that the measurement state is not the first state, that is, the measurement state is the second state ("No" in step S401), the relative humidity measurement unit 207 performs a second humidity measurement process (step S403). Specifically, the relative humidity measurement unit 207 measures the water vapor pressure P W , the saturated water vapor pressure P WS and calculate the relative humidity of the gas mixture using equation (21) above.

[0174] (4) Advantages As described above, the physical quantity measurement system 1 according to this embodiment includes the temperature and humidity sensor 16, the heat generating unit 17, the heat generation control unit 203, and the water vapor pressure measurement unit 204. The temperature and humidity sensor 16 measures the humidity and temperature of the mixed gas flowing through the flow path 101. The heat generating unit 17 generates heat to warm the temperature and humidity sensor 16. The heat generation control unit 203 controls the on / off state of the heat generating unit 17 to switch the state of the heat generating unit 17 between an on state in which the heat generating operation is performed and an off state in which the heat generating operation is stopped. The water vapor pressure measurement unit 204 measures the water vapor pressure of the water vapor contained in the mixed gas. The heat generation control unit 203 controls the on / off state of the heat generating unit 17 based on a comparison result between the humidity measurement value of the mixed gas measured by the temperature and humidity sensor 16 and a threshold value. The water vapor pressure measurement unit 204 measures the water vapor pressure of the water vapor based on the humidity measurement value and the temperature measurement value of the mixed gas measured by the temperature and humidity sensor 16, regardless of the state of the heat generating unit 17.

[0175] According to this configuration, even when the mixed gas flows through the flow path in a high-humidity environment, it is possible to reduce the possibility of condensation occurring on the temperature and humidity sensor 16 by controlling the heat generation operation of the heat generating unit 17. Therefore, even when the mixed gas flows through the flow path in a high-humidity environment, it is possible to more accurately measure the water vapor pressure of the mixed gas.

[0176] (5) Variations Modifications are listed below. The modifications described below can be applied in appropriate combination with the above-described embodiment.

[0177] (5.1) Variation 1 In the embodiment, the processing device 20 is configured to switch the measurement state using the first threshold and the second threshold, that is, to switch the measurement method using the first threshold and the second threshold, but is not limited to this configuration.

[0178] The processing device 20 may switch between measurement methods using one threshold value. The third measurement process in the first modification will be described below with reference to FIG.

[0179] The water vapor pressure measuring unit 204 determines whether the humidity measurement value obtained by the second signal processing unit 202 is greater than a predetermined threshold value (step S501). For example, the predetermined threshold value is the above-mentioned second threshold value.

[0180] If it is determined that the humidity measurement value is not greater than the predetermined threshold (second threshold), that is, the humidity measurement value is equal to or less than the second threshold ("No" in step S501), the water vapor pressure measurement unit 204 performs a first water vapor pressure calculation process (step S502). Specifically, the water vapor pressure measurement unit 204 calculates the water vapor pressure P W After that, the concentration measurement unit 205 performs a first water vapor concentration calculation process (step S503). The concentration measurement unit 205 calculates the water vapor pressure P W and the pressure P of the mixed gas obtained by the second signal processing unit 202 m Using the above equation (3), the water vapor concentration x of the water vapor contained in the mixed gas is w Measure.

[0181] When it is determined that the humidity measurement value is greater than the predetermined threshold (second threshold) ("Yes" in step S501), the water vapor pressure measurement unit 204 performs a second water vapor pressure calculation process (step S504). Specifically, the water vapor pressure measurement unit 204 calculates the water vapor pressure P W Thereafter, the concentration measurement unit 205 performs a second water vapor concentration calculation process (step S505). The concentration measurement unit 205 calculates the water vapor pressure P W and the pressure P of the mixed gas obtained by the second signal processing unit 202 m Using the above equation (3), the water vapor concentration x of the water vapor contained in the mixed gas is w Measure.

[0182] Furthermore, in Modification 1, when the processing device 20 performs a relative humidity measurement process, in step S401, the relative humidity measurement unit 207 determines whether the measured humidity value is greater than a predetermined threshold value, instead of determining whether the measurement state is the first state. If it determines that the measured humidity value is not greater than the predetermined threshold value (second threshold value), that is, if it determines that the measured humidity value is equal to or less than the second threshold value, the relative humidity measurement unit 207 performs a first humidity measurement process shown in step S402. If it determines that the measured humidity value is greater than the predetermined threshold value (second threshold value), the relative humidity measurement unit 207 performs a second humidity measurement process shown in step S403.

[0183] In step S501, the water vapor pressure measurement unit 204 may set the measurement state to the second measurement state if it determines that the humidity measurement value is greater than a predetermined threshold (second threshold), and may set the measurement state to the first measurement state if it determines that the humidity measurement value is not greater than the predetermined threshold (second threshold). In this case, there is no need to change step S401 in the relative humidity measurement process as described above.

[0184] (5.2) Variation 2 When the control unit 25 of the processing device 20 detects an abnormality in the heat generation operation, the control unit 25 may control the power supply unit 26 to stop supplying power to at least the heat generation unit 17 among the sensors and the heat generation unit 17 provided in the flow path main body 10.

[0185] (5.3) Variation 3 In the embodiment, the ultrasonic propagation path 106 is configured to be a path formed by arranging a pair of ultrasonic transmitters and receivers 11 and 12 so as to be inclined at an angle θ with respect to the flow path 101, that is, a so-called Z-path type path, but is not limited to this configuration.

[0186] As an ultrasonic propagation path, a path formed by arranging a pair of ultrasonic transmitters and receivers 11 and 12 so that the ultrasonic waves cross the flow of the mixed gas in the flow path 101 twice, or a path formed by a method involving reflection such as a so-called V-path method, may be used.

[0187] (5.4) Variation 4 In the embodiment, the mixed gas contains nitrogen as a gas other than hydrogen, but is not limited to this configuration. The mixed gas may contain gases other than nitrogen as a gas other than hydrogen, such as hydrocarbons (HC-based) such as methane, carbon dioxide, helium, argon, and oxygen.

[0188] (Other variations) The above embodiment is merely one of various embodiments of the present disclosure, and various modifications can be made to the above embodiment depending on the design and the like as long as the object of the present disclosure can be achieved.

[0189] Furthermore, functions similar to those of the physical quantity measurement system 1 may be embodied as a physical quantity measurement method, a computer program, or a non-transitory recording medium on which a program is recorded. A physical quantity measurement method according to one aspect is used in a physical quantity measurement system 1 including a temperature and humidity sensor 16 and a heat generating unit 17. The temperature and humidity sensor 16 measures the humidity and temperature of a gas mixture flowing through a flow path 101. The heat generating unit 17 generates heat to warm the temperature and humidity sensor 16. The physical quantity measurement method includes a heat generation control step and a water vapor pressure measurement step. The heat generation control step performs on / off control on the heat generating unit 17 to switch the state of the heat generating unit 17 between an on state in which the heat generating operation is performed and an off state in which the heat generating operation is stopped. The water vapor pressure measurement step measures the water vapor pressure of water vapor contained in the gas mixture. The heat generation control step performs on / off control on the heat generating unit 17 based on a comparison result between the humidity measurement value of the gas measured by the temperature and humidity sensor 16 and a threshold value. In the water vapor pressure measurement step, the water vapor pressure of water vapor is measured based on the humidity measurement value and the temperature measurement value of the mixed gas measured by the temperature and humidity sensor 16, regardless of the state of the heat generating unit 17. A program according to one aspect is a program for causing a computer system to function as the above-described physical quantity measurement method.

[0190] The physical quantity measurement system 1 according to the present disclosure includes a computer system. The computer system is primarily composed of a processor and a memory as hardware. The processor executes a program stored in the memory of the computer system to realize the functions of the physical quantity measurement system 1 according to the present disclosure. The program may be pre-stored in the memory of the computer system, provided via a telecommunications line, or provided in a non-transitory recording medium such as a memory card, optical disk, or hard disk drive that is readable by the computer system. The processor of the computer system is composed of one or more electronic circuits including a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). The integrated circuits, such as ICs and LSIs, are referred to by different names depending on the degree of integration, and include integrated circuits called system LSIs, very large-scale integrations (VLSIs), and ultra-large-scale integrations (ULSIs). Furthermore, field-programmable gate arrays (FPGAs), which are programmable after the LSI is manufactured, or logic devices that allow the reconfiguration of internal connections or internal circuit partitions of the LSI, can also be used as processors. The electronic circuits may be integrated into one chip or distributed across multiple chips. The chips may be integrated into one device or distributed across multiple devices. The computer system referred to here includes a microcontroller having one or more processors and one or more memories. Therefore, the microcontroller is also composed of one or more electronic circuits including a semiconductor integrated circuit or a large-scale integrated circuit.

[0191] Furthermore, it is not essential for the physical quantity measurement system 1 that multiple functions in the physical quantity measurement system 1 are concentrated in one housing, and the components of the physical quantity measurement system 1 may be distributed across multiple housings. Furthermore, at least some of the functions of the physical quantity measurement system 1 may be realized by the cloud (cloud computing) or the like.

[0192] (summary) As described above, the physical quantity measuring system (1) of the first aspect includes a temperature and humidity sensor (16), a heat generating unit (17), a heat generation control unit (203), and a water vapor pressure measuring unit (204). The temperature and humidity sensor (16) measures the humidity and temperature of the mixed gas flowing through the flow path (101). The heat generating unit (17) performs a heat generating operation to generate heat for warming the temperature and humidity sensor (16). The heat generation control unit (203) performs on / off control of the heat generating unit (17) to switch the state of the heat generating unit (17) between an on state in which the heat generating operation is performed and an off state in which the heat generating operation is stopped. The water vapor pressure measuring unit (204) measures the water vapor pressure of water vapor contained in the mixed gas. The heat generation control unit (203) performs on / off control of the heat generating unit (17) based on a result of comparing the humidity measurement value of the mixed gas measured by the temperature and humidity sensor (16) with a threshold value. The water vapor pressure measuring unit (204) measures the water vapor pressure of water vapor based on the measured humidity value and the measured temperature value of the gas mixture measured by the temperature and humidity sensor (16), regardless of the state of the heat generating unit (17).

[0193] According to this embodiment, by controlling the heat generation operation of the heat generating portion (17), it is possible to reduce the possibility of condensation on the temperature and humidity sensor (16) even when the mixed gas flows through the flow path in a high-humidity environment, and as a result, it is possible to more accurately measure the water vapor pressure of the mixed gas even when the mixed gas flows through the flow path in a high-humidity environment.

[0194] The physical quantity measuring system (1) of the second aspect is the same as that of the first aspect, but further includes a pressure sensor (15) and a concentration measuring unit (205). The pressure sensor (15) measures the pressure of the mixed gas. The concentration measuring unit (205) measures the water vapor concentration of the water vapor contained in the mixed gas based on the water vapor pressure measured by the water vapor pressure measuring unit (204) and the mixed gas pressure measured by the pressure sensor (15).

[0195] According to this embodiment, the water vapor concentration of the water vapor contained in the mixed gas is measured using the water vapor pressure measured by the water vapor pressure measuring unit (204), so that the water vapor concentration can be measured more accurately.

[0196] The physical quantity measuring system (1) of the third aspect is the same as that of the second aspect, and further includes a pair of ultrasonic transmitters and receivers (11, 12). The pair of ultrasonic transmitters and receivers (11, 12) transmit and receive ultrasonic waves. The pair of ultrasonic transmitters and receivers (11, 12) are arranged so that the ultrasonic waves cross the flow of the mixed gas in the flow path (101). The concentration measuring unit (205) further measures a gas concentration, which is the concentration of a gas other than water vapor contained in the mixed gas, based on the water vapor concentration and the propagation time of the ultrasonic waves through the pair of ultrasonic transmitters and receivers (11, 12).

[0197] According to this embodiment, the water vapor concentration measured by the concentration measuring unit (205) is used to measure the gas concentration, which is the concentration of a gas contained in the mixed gas but different from water vapor, so that the gas concentration can be measured more accurately.

[0198] The physical quantity measuring system (1) of the fourth aspect is the third aspect, further including a flow rate measuring unit (206). The flow rate measuring unit (206) measures the flow rate of the mixed gas in the flow path (101) using the propagation time of the ultrasonic waves, the water vapor concentration, and the gas concentration, and measures the flow rate of the gas using the flow rate of the mixed gas.

[0199] According to this aspect, the flow rate of the mixed gas is measured using the water vapor concentration and gas concentration measured by the concentration measuring unit (205), so that the flow rate of the mixed gas can be measured more accurately.

[0200] The physical quantity measuring system (1) of a fifth aspect is the physical quantity measuring system of any one of the first to fourth aspects, further including a temperature sensor (e.g., the second temperature sensor 14) and a relative humidity measuring unit (207). The temperature sensor measures the temperature of the mixed gas and is installed at a location where the influence of the heat generated by the heat generating unit (17) is smaller than that of the temperature and humidity sensor (16). The relative humidity measuring unit (207) measures the relative humidity of the mixed gas based on the water vapor pressure measured by the water vapor pressure measuring unit (204) and the saturated water vapor pressure corresponding to the temperature obtained from the temperature sensor.

[0201] According to this embodiment, the temperature sensor is less affected by the heat generated by the heat generating element (17) than the temperature / humidity sensor (16), and therefore can measure the temperature in the flow path (101) more accurately than the temperature measured by the temperature / humidity sensor (16). Furthermore, when the heat generating element (17) is in the on state, the temperature / humidity sensor (16) is affected by the heat generated by the heat generating element (17), and therefore cannot measure the temperature in the flow path (101) accurately. Therefore, by using the temperature measured by the temperature sensor, the temperature in the flow path (101) can be measured more accurately even when the heat generating element (17) is in the on state. As a result, the relative humidity can be measured more accurately.

[0202] In the physical quantity measuring system (1) of the sixth aspect, in any one of the first to fifth aspects, the threshold value is a humidity value at which condensation does not occur on the temperature and humidity sensor (16).

[0203] According to this embodiment, the threshold value is set to a humidity value at which condensation does not occur on the temperature and humidity sensor (16), thereby reducing the possibility of condensation occurring on the temperature and humidity sensor (16). This makes it possible to suppress a decrease in measurement accuracy due to condensation occurring on the temperature and humidity sensor (16), thereby enabling more accurate measurement of the water vapor pressure of the mixed gas.

[0204] In the physical quantity measuring system (1) of the seventh aspect, in any of the first to sixth aspects, when the humidity measurement value is greater than a threshold value, the heat generation control unit (203) controls the period during which the heat generation unit (17) is in an on state and an off state by pulse width modulation to alternately switch between the on state and the off state, and controls the pulse width of the pulse width modulation so that the on state becomes longer as the difference between the threshold value and the humidity measurement value increases. When the humidity measurement value is equal to or less than the threshold value, the heat generation control unit (203) turns the heat generation unit (17) into an off state.

[0205] According to this embodiment, the possibility of condensation forming on the temperature and humidity sensor (16) can be reduced. [Explanation of symbols]

[0206] 1 Physical quantity measurement system 11 Ultrasonic transmitter / receiver (first ultrasonic transmitter / receiver) 12 Ultrasonic transmitter / receiver (second ultrasonic transmitter / receiver) 13 First temperature sensor 14 Second temperature sensor (temperature sensor) 15 Pressure Sensor 16 Temperature and humidity sensor 17 Heat generating part 101 Flow path 203 Heating control unit 204 Water vapor pressure measurement unit 205 Concentration measurement unit 206 Flow Meter 207 Relative humidity measurement section

Claims

1. a temperature and humidity sensor that measures the humidity and temperature of the mixed gas flowing through the flow path; a heat generating unit that generates heat to warm the temperature and humidity sensor; a heat generation control unit that performs on / off control of the heat generation unit to switch the state of the heat generation unit between an on state in which the heat generation operation is performed and an off state in which the heat generation operation is stopped; a water vapor pressure measuring unit that measures the water vapor pressure of the water vapor contained in the mixed gas, the heat generation control unit performs the on / off control on the heat generation unit based on a comparison result between a humidity measurement value of the mixed gas measured by the temperature and humidity sensor and a threshold value, the water vapor pressure measuring unit measures the water vapor pressure of the water vapor contained in the mixed gas based on the humidity measurement value and the temperature measurement value of the mixed gas measured by the temperature and humidity sensor, regardless of the state of the heat generating unit. Physical quantity measurement system.

2. a pressure sensor that measures the pressure of the mixed gas; a concentration measuring unit that measures a water vapor concentration of the water vapor contained in the mixed gas based on the water vapor pressure measured by the water vapor pressure measuring unit and the pressure of the mixed gas measured by the pressure sensor, The physical quantity measuring system according to claim 1 .

3. a pair of ultrasonic transducers arranged to transmit and receive ultrasonic waves so that the ultrasonic waves cross the flow of the mixed gas in the flow channel; The concentration measurement unit further measures a gas concentration, which is a concentration of a gas that is contained in the mixed gas and is different from the water vapor, based on the water vapor concentration and a propagation time of the ultrasonic waves through the pair of ultrasonic transmitter-receivers. The physical quantity measuring system according to claim 2 .

4. a flow rate measuring unit that measures a flow rate of the mixed gas in the flow path using a propagation time of the ultrasonic wave, the water vapor concentration, and the gas concentration, and that measures a flow rate of the gas using the flow rate of the mixed gas; The physical quantity measuring system according to claim 3 .

5. a temperature sensor that measures the temperature of the mixed gas and is installed at a location where the influence of heat generated by the heat generating portion is smaller than that of the temperature and humidity sensor; a relative humidity measuring unit that measures the relative humidity of the mixed gas based on the water vapor pressure measured by the water vapor pressure measuring unit and a saturated water vapor pressure according to the temperature obtained from the temperature sensor, The physical quantity measuring system according to any one of claims 1 to 4.

6. The threshold value is a humidity value at which condensation does not occur on the temperature and humidity sensor. The physical quantity measuring system according to any one of claims 1 to 4.

7. The heat generation control unit When the humidity measurement value is greater than the threshold value, the period during which the heat generating unit is in the on state and the period during which the heat generating unit is in the off state are controlled by pulse width modulation to alternately switch between the on state and the off state, and the pulse width in the pulse width modulation is controlled so that the on state becomes longer as the difference between the threshold value and the humidity measurement value increases; When the humidity measurement value is equal to or less than the threshold value, the heating unit is turned off. The physical quantity measuring system according to any one of claims 1 to 4.

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