Thermal type flowmeter, and correction method

Abstract

To enable measuring a flow rate more accurately even when a fluid of a measurement object is unknown.SOLUTION: A fifth circuit 111 is configured to obtain thermal conductivity of a fluid as to each of temperature differences a third circuit 109 obtains from a temperature difference the third circuit 109 obtains, consumption power a fourth circuit 110 obtains, a distance between diffusion temperature measurement units 107a, 107b and 107c measuring a temperature measurement value and a temperature adjustment unit 102, and a cross-section area of piping. A sixth circuit 112 is configured to obtain a temperature characteristic of the thermal conductivity of the fluid from each thermal conductivity obtained by the fifth circuit 111. A seventh circuit 113 is configured to obtain a correction value correcting a sensor value by the temperature characteristic of the thermal conductivity of the fluid the sixth circuit 112 obtains.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermal flow meter and a correction method. [Background technology]

[0002] Thermal flow meters include a method of measuring the flow rate from the temperature difference between the upstream and downstream of a heater, and a method of measuring the flow rate from the power consumption of the heater. For example, when measuring the flow rate of a liquid, the heater is operated by heating drive to a constant temperature, such as 10°C above the liquid temperature, and the flow rate is calculated from the temperature difference between the upstream and downstream or the power of the heater (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-010322 Summary of the Invention [Problem to be solved by the invention]

[0004] In this way, thermal flow meters convert heater output, such as the heater temperature difference and heater power, into flow rate. This conversion (conversion formula) is specific to the fluid being measured. For this reason, if the type or physical properties of the fluid being measured are unknown, or if the measurement target is changed, errors may occur when converting heater output to flow rate, and an accurate flow rate may not be output.

[0005] The present invention has been made to solve the above problems, and has as its object to measure the flow rate with higher accuracy even when the fluid to be measured is unknown. [Means for solving the problem]

[0006] The thermal flow meter according to the present invention includes a pipe for transporting a fluid to be measured, a temperature control unit configured to heat or cool the fluid in a measurement area of ​​the pipe, a sensor circuit configured to output a sensor value corresponding to the state of thermal diffusion in the fluid heated by the temperature control unit when the temperature control unit is driven so that the difference between a reference temperature and the temperature of the temperature control unit becomes a set temperature difference, a fluid stopping unit configured to stop the flow of the fluid, a first circuit configured to start driving the temperature control unit after causing the fluid stopping unit to stop the flow of the fluid, diffusion temperature measurement units arranged at multiple locations away from the temperature control unit in the axial direction of the pipe and measuring the temperature of the fluid at positions affected by the temperature caused by the temperature control unit when the fluid stopping unit stops the flow of the fluid, a second circuit configured to cause the temperature control unit to perform multiple temperature controls after the temperature control unit starts driving, and a second circuit configured to control the temperature caused by the temperature control unit by the second circuit. The temperature control system includes a third circuit configured to calculate the difference between a temperature measurement value different from that of the temperature control unit measured by the diffusion temperature measurement unit and the temperature of the temperature control unit in each of a plurality of temperature controls; a fourth circuit configured to calculate the power consumption of the temperature control unit at the time the third circuit calculates the temperature difference in each of a plurality of temperature controls by the temperature control unit using the second circuit; a fifth circuit configured to calculate the thermal conductivity of the fluid for each temperature difference calculated by the fourth circuit from the temperature difference calculated by the third circuit, the power consumption calculated by the fourth circuit, the distance between the diffusion temperature measurement unit that measured the temperature measurement value and the temperature control unit, and the cross-sectional area of ​​the piping; a sixth circuit configured to calculate the temperature characteristics of the thermal conductivity of the fluid from each thermal conductivity calculated by the fifth circuit; a seventh circuit configured to calculate a correction value by correcting the sensor value using the temperature characteristics of the thermal conductivity of the fluid calculated by the sixth circuit; and an eighth circuit configured to calculate the flow rate of the fluid from the correction value.

[0007] In one example of the configuration of the thermal flow meter, the sensor circuit outputs the power of the temperature adjustment unit as a sensor value when the temperature adjustment unit is driven so that the difference between the temperature of the temperature adjustment unit and the reference temperature becomes the set temperature difference.

[0008] In one configuration example of the above thermal flow meter, there is provided a first fluid temperature measuring unit that measures a first temperature of the fluid at a position upstream of the temperature adjustment unit and affected by the heat of the temperature adjustment unit, and a second fluid temperature measuring unit that measures a second temperature of the fluid at a position downstream of the temperature adjustment unit and affected by the heat of the temperature adjustment unit, at least one of the first fluid temperature measuring unit and the second fluid temperature measuring unit is a diffusion temperature measuring unit adjacent to the temperature adjustment unit, and the sensor circuit outputs the temperature difference between the first temperature and the second temperature as a sensor value when the temperature adjustment unit is driven so that the difference between the temperature of the temperature adjustment unit and the reference temperature becomes the set temperature difference.

[0009] In one example of the thermal flow meter, a reference temperature measurement unit is provided that measures, as the reference temperature, the temperature of the fluid at a reference temperature measurement position upstream of the temperature adjustment unit and not affected by the heat of the temperature adjustment unit.

[0010] In one configuration example of the thermal flow meter described above, the thermal flow meter further includes a ninth circuit that receives information that the fluid has been changed and starts operation of the first circuit.

[0011] Furthermore, a correction method according to the present invention is a method for correcting a sensor value corresponding to a state of thermal diffusion in a fluid heated by a temperature control unit when the temperature control unit is driven so that the difference between the temperature of the temperature control unit that heats or cools the fluid in a measurement region of a pipe that transports the fluid to be measured and a reference temperature becomes a set temperature difference, the method comprising: a first step of stopping the flow of the fluid and then starting to drive the temperature control unit; a second step of causing the temperature control unit to perform a plurality of temperature controls after the temperature control unit starts to drive; and a temperature measurement value of the temperature control unit, which is different from that measured by the temperature control unit and is measured by diffusion temperature measurement units that are arranged at a plurality of locations away from the temperature control unit in the axial direction of the pipe and measure the temperature of the fluid at positions that are affected by the temperature of the temperature control unit, in each of the plurality of temperature controls by the temperature control unit in the second step. a third step of calculating the difference between the temperature and the temperature; a fourth step of calculating the power consumption of the temperature control unit at the time the temperature difference was calculated in the third step for each of the multiple temperature controls by the temperature control unit in the second step; a fifth step of calculating the thermal conductivity of the fluid for each of the temperature differences calculated in the fourth step from the temperature difference calculated in the third step, the power consumption calculated in the fourth step, the distance between the diffusion temperature measurement unit that measured the temperature measurement value and the temperature control unit, and the cross-sectional area of ​​the piping; a sixth step of calculating the temperature characteristics of the thermal conductivity of the fluid from each thermal conductivity calculated in the fifth step; a seventh step of calculating the sensor value; an eighth step of calculating a correction value by correcting the sensor value using the temperature characteristics of the thermal conductivity of the fluid calculated in the sixth step; and a ninth step of calculating the flow rate of the fluid from the correction value.

[0012] In one example of the above correction method, the seventh step is a correction method in which the power of the temperature adjustment unit when the temperature adjustment unit is driven so that the difference between the temperature of the temperature adjustment unit and the reference temperature becomes the set temperature difference is used as the sensor value.

[0013] In one example configuration of the above correction method, the seventh step sets the sensor value to the temperature difference between a first temperature of the fluid measured at a position upstream of the temperature adjustment unit that is subject to the thermal influence of the temperature adjustment unit and a second temperature of the fluid measured at a position downstream of the temperature adjustment unit that is subject to the thermal influence of the temperature adjustment unit when the temperature adjustment unit is driven so that the difference between the temperature of the temperature adjustment unit and the reference temperature becomes the set temperature difference.

[0014] In one example of the above correction method, the seventh step is a correction method in which the temperature of the fluid is measured at a reference temperature measurement position that is upstream of the temperature adjustment unit and is not affected by the heat of the temperature adjustment unit, and the measured temperature is used as the reference temperature. [Effects of the Invention]

[0015] As described above, according to the present invention, the thermal conductivity of the fluid transported through the piping is determined by measuring the temperature of the fluid at a position affected by the temperature of the temperature control unit using diffusion temperature measurement units arranged at multiple locations, so that the flow rate can be measured more accurately even if the fluid to be measured is unknown. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a configuration diagram showing the configuration of a thermal flow meter according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a characteristic diagram showing the temperature characteristics of the thermal conductivity of water. [Figure 3] FIG. 3 is a flowchart illustrating the correction method according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a configuration diagram showing the configuration of another thermal flow meter according to the first embodiment of the present invention. [Figure 5] FIG. 5 is a configuration diagram showing the configuration of a thermal flow meter according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a flowchart illustrating an example of the operation of the thermal flow meter according to the second embodiment of the present invention. [Figure 7] FIG. 7 is a configuration diagram showing a partial hardware configuration of a thermal flow meter according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] A thermal flow meter according to an embodiment of the present invention will now be described.

[0018] [Embodiment 1] First, a thermal flow meter according to a first embodiment of the present invention will be described with reference to Fig. 1. This thermal flow meter includes a pipe 101, a temperature adjustment unit 102, a reference temperature measurement unit 103, a sensor circuit 104, a first valve 105a, a second valve 105b, a first circuit 106, diffusion temperature measurement units 107a, 107b, and 107c, a second circuit 108, a third circuit 109, a fourth circuit 110, a fifth circuit 111, a sixth circuit 112, a seventh circuit 113, and an eighth circuit 114.

[0019] Pipe 101 transports a fluid to be measured. Temperature adjustment unit 102 heats or cools the fluid in a measurement region of pipe 101. Temperature adjustment unit 102 can be configured, for example, from a heating element (or cooling element) such as a heater or Peltier element. Temperature adjustment unit 102 can also be configured, for example, from a cooling element such as a Peltier element.

[0020] The sensor circuit 104 outputs a sensor value corresponding to the state of thermal diffusion in the fluid heated by the temperature adjustment unit 102 when the temperature adjustment unit 102 is driven so that the difference between the reference temperature and the temperature of the temperature adjustment unit 102 becomes the set temperature difference. In this example, the sensor circuit 104 outputs the power of the temperature adjustment unit 102 as the sensor value when the temperature adjustment unit 102 is driven so that the difference between the temperature of the temperature adjustment unit 102 and the reference temperature becomes the set temperature difference.

[0021] The sensor circuit 104 supplies power to the temperature adjustment unit 102 and controls the supplied power. For example, the sensor circuit 104 adjusts the drive voltage to be supplied by feedback controlling the voltage supplied to the bridge circuit that constitutes the temperature adjustment unit 102 so that the output voltage of the bridge circuit becomes zero.

[0022] Here, in the first embodiment, a reference temperature measurement unit 103 is provided that measures the temperature of the fluid at a reference temperature measurement position that is upstream of the temperature adjustment unit 102 and is not affected by the heat of the temperature adjustment unit 102, and the temperature of the fluid measured by the reference temperature measurement unit 103 is used as the reference temperature. Note that a preset reference temperature can be used without using the reference temperature measurement unit 103.

[0023] The reference temperature measurement unit 103 measures the temperature of the fluid at the reference temperature measurement position. The reference temperature measurement unit 103 can be, for example, a temperature sensor element such as a thermopile configured from a wiring pattern that configures multiple thermocouples.

[0024] The first valve 105a and the second valve 105b constitute a fluid stopping unit. The first valve 105a is arranged upstream of the reference temperature measurement unit 103. The second valve 105b is arranged downstream of the temperature adjustment unit 102. The flow of the fluid through the pipe 101 can be stopped by fully closing the first valve 105a and the second valve 105b.

[0025] Diffusion temperature measuring units 107a, 107b, and 107c are arranged at multiple locations away from temperature adjusting unit 102 in the axial direction of pipe 101, and measure the temperature of the fluid at locations affected by the temperature of temperature adjusting unit 102 when the fluid flow is stopped by the fluid stopping unit formed by first valve 105a and second valve 105b. Diffusion temperature measuring units 107a, 107b, and 107c can be configured from temperature sensors similar to those of reference temperature measuring unit 103. In this example, diffusion temperature measuring units 107a, 107b, and 107c are arranged at three locations, but the number of locations is not limited to three, and they can also be arranged at two locations, or four or more locations.

[0026] The first circuit 106 stops the flow of fluid at the fluid stopping section using the first valve 105a and the second valve 105b, and then starts driving the temperature adjustment unit 102. The second circuit 108 causes the temperature adjustment unit 102 to perform multiple temperature controls after the temperature adjustment unit 102 starts driving. For example, the second circuit 108 controls the temperature adjustment unit 102 to three temperatures: a + 10°C, a + 20°C, and a + 30°C, where a is the fluid temperature a measured by the reference temperature measurement unit 103.

[0027] The third circuit 109 calculates the difference between the temperature measured by the diffusion temperature measuring units 107a, 107b, and 107c, which are different from the temperature of the temperature adjusting unit 102, and the temperature of the temperature adjusting unit 102, in each of the multiple temperature controls by the temperature adjusting unit 102 controlled by the second circuit 108.

[0028] Here, the diffusion temperature measuring unit 107a near the temperature adjustment unit 102 tends to have the same temperature as the temperature adjustment unit 102. As a result, for example, the temperature difference between the temperature adjustment unit 102 and the diffusion temperature measuring unit 107a may become zero, making it impossible to calculate the thermal conductivity of the fluid. For this reason, the diffusion temperature measuring units 107a, 107b, and 107c are provided at multiple locations so that the above-mentioned temperature difference can be determined. Using any of the diffusion temperature measuring units 107a, 107b, and 107c makes it possible to determine the above-mentioned temperature difference. Furthermore, using a temperature measurement value different from that of the temperature adjustment unit 102 measured by the diffusion temperature measuring units 107a, 107b, and 107c can calculate the thermal conductivity of the fluid.

[0029] The fourth circuit 110 calculates the power consumption of the temperature adjustment unit 102 at the time when the third circuit 109 calculates the temperature difference in each of the multiple temperature controls performed by the temperature adjustment unit 102 by the second circuit 108. The fourth circuit 110 can calculate the drive power of the temperature adjustment unit 102, for example, from the voltage applied to the heating element (or cooling element) that constitutes the temperature adjustment unit 102 and the voltage applied to the bridge circuit that includes this element.

[0030] The fifth circuit 111 calculates the thermal conductivity of the fluid for each temperature difference calculated by the third circuit 109 from the temperature difference calculated by the third circuit 109, the power consumption calculated by the fourth circuit 110, the distance between the temperature adjustment unit 102 and the diffusion temperature measurement units 107a, 107b, and 107c that measured the temperature measurements, and the cross-sectional area of ​​the pipe 101. It is known that thermal conductivity can be calculated from Fourier's law by the formula "thermal conductivity = (heat flow rate × length) ÷ (cross-sectional area × temperature difference)." Here, the "heat flow rate" can be the power consumption (W) of the temperature adjustment unit 102. The "length" is the distance between the temperature adjustment unit 102 and the diffusion temperature measurement units 107a, 107b, and 107c that measured the temperature measurements. The "cross-sectional area" is the cross-sectional area of ​​the pipe 101. The "temperature difference" is the temperature difference calculated by the third circuit 109. It should be noted that by using the temperature measurement result of the diffusion temperature measurement unit 107a closest to the temperature adjustment unit 102, the accuracy of the calculation result is improved.

[0031] The sixth circuit 112 determines the temperature characteristics of the thermal conductivity of the fluid from the respective thermal conductivities determined by the fifth circuit 111. For example, as shown in Fig. 2, the sixth circuit 112 determines the relationship between the multiple temperatures of the temperature adjustment unit 102 controlled by the second circuit 108 and the changes in the respective thermal conductivities determined by the fifth circuit 111. Note that Fig. 2 shows the temperature characteristics of the thermal conductivity when the fluid is water.

[0032] The seventh circuit 113 obtains a correction value by correcting the sensor value using the temperature characteristics of the thermal conductivity of the fluid obtained by the sixth circuit 112. The eighth circuit 114 calculates the flow rate of the fluid from the correction value obtained by the seventh circuit 113. The first circuit 106, the second circuit 108, the third circuit 109, the fourth circuit 110, the fifth circuit 111, the sixth circuit 112, and the seventh circuit 113 form a correction unit.

[0033] As mentioned above, when the type or physical properties of the fluid to be measured are unknown or when the measurement target is changed, errors may occur when converting the heater output to a flow rate, making it impossible to output an accurate flow rate. To address this issue, a technique has been proposed in which the heater (temperature control unit 102) is heated while the flow of fluid is stopped, and a correction coefficient is calculated and corrected from the heater's power consumption. However, the temperature of the fluid flowing through the pipe 101 is not constant, and the thermal conductivity of the fluid has temperature characteristics, so the value of the thermal conductivity also changes as the temperature of the fluid changes.

[0034] Here, by determining the temperature characteristics of the thermal conductivity of the fluid as described above, the sensor value can be corrected more accurately.

[0035] Next, a correction method according to the first embodiment of the present invention will be described with reference to Fig. 3. This correction method obtains a correction value obtained by correcting a sensor value corresponding to the state of thermal diffusion in a fluid heated by temperature adjustment unit 102 when temperature adjustment unit 102 is driven so that the difference between the temperature of the fluid at a reference temperature measurement position that is upstream of temperature adjustment unit 102 that heats or cools the fluid and is not affected by the heat of temperature adjustment unit 102 in a measurement region that transports the fluid to be measured, and the temperature of temperature adjustment unit 102, becomes a set temperature difference.

[0036] First, in a first step S101, the first circuit 106 stops the flow of fluid at the fluid stopping section using the first valve 105a and the second valve 105b, and then starts driving the temperature adjustment unit 102. Next, in a second step S102, the second circuit 108 starts driving the temperature adjustment unit 102, and then causes the temperature adjustment unit 102 to perform multiple temperature controls.

[0037] Next, in a third step S103, in each of the multiple temperature controls by the temperature control unit 102 in the second step S102, the third circuit 109 calculates the difference between the temperature measurement value different from that of the temperature control unit 102 measured by a diffusion temperature measurement unit that is arranged at multiple locations away from the temperature control unit 102 in the axial direction of the piping and measures the temperature of the fluid at a position affected by the temperature by the temperature control unit 102 and the temperature of the temperature control unit 102.

[0038] Next, in a fourth step S104, in each of the plurality of temperature controls by the temperature adjustment unit 102 in the second step S102, the fourth circuit 110 calculates the power consumption of the temperature adjustment unit 102 at the time when the temperature difference was calculated in the third step S103.

[0039] Next, in a fifth step S105, the fifth circuit 111 calculates the thermal conductivity of the fluid for each of the temperature differences calculated in the third step S103 from the temperature difference calculated in the third step S103, the power consumption calculated in the fourth step S104, the distance between the diffusion temperature measurement units 107a, 107b, and 107c that measured the temperature values ​​and the temperature adjustment unit 102, and the cross-sectional area of ​​the piping 101.

[0040] Next, in a sixth step S106, the sixth circuit 112 determines the temperature characteristic of the thermal conductivity of the fluid from the respective thermal conductivities determined in the fifth step S105. Thereafter, in a seventh step S107, the first valve 105a and the second valve 105b are fully opened to establish a steady state in which the fluid flows, and then the sensor circuit 104 is operated to determine (output) a sensor value. Next, in an eighth step S108, the seventh circuit 113 determines a correction value by correcting the sensor value output from the sensor circuit 104 using the temperature characteristic of the thermal conductivity of the fluid determined in the sixth step S106. Next, in a ninth step S109, the eighth circuit 114 calculates the flow rate of the fluid using the correction value determined in the seventh step S107.

[0041] The sensor value can be determined by the configuration of the thermal flow meter shown in Fig. 4. This thermal flow meter includes a reference temperature measurement unit 103a that measures the temperature of the fluid at a reference temperature measurement position, a first fluid temperature measurement unit that measures a first temperature of the fluid at a position upstream of the temperature adjustment unit 102 and affected by the heat of the temperature adjustment unit 102, and a second fluid temperature measurement unit 103b that measures a second temperature of the fluid at a position downstream of the temperature adjustment unit 102 and affected by the heat of the temperature adjustment unit 102. Here, the first fluid temperature measurement unit can be a diffusion temperature measurement unit 107a adjacent to the temperature adjustment unit 102. Note that the second valve 105b is omitted in Fig. 4.

[0042] The sensor circuit 104a outputs, as a sensor value, the temperature difference between the first temperature and the second temperature when the temperature adjustment unit 102 is driven so that the difference between the temperature of the temperature adjustment unit 102 and the temperature of the fluid measured by the reference temperature measurement unit 103a becomes the set temperature difference. Note that, without using the reference temperature measurement unit 103a, the sensor circuit 104a can output, as a sensor value, the temperature difference between the first temperature and the second temperature when the temperature adjustment unit 102 is driven so that the difference between the temperature of the temperature adjustment unit 102 and the set reference temperature becomes the set temperature difference.

[0043] In the above description, the diffusion temperature measurement units 107a, 107b, and 107c are arranged on the upstream side of the pipe 101, but this is not limiting. The diffusion temperature measurement units may be arranged at multiple locations on the downstream side of the pipe 101. In this case, the first fluid temperature measurement unit is arranged upstream of the temperature adjustment unit 102 and measures the temperature of the fluid at a position that is affected by the heat of the temperature adjustment unit 102. The second fluid temperature measurement unit may be a diffusion temperature measurement unit adjacent to the temperature adjustment unit 102 on the downstream side. The diffusion temperature measurement units may be arranged at multiple locations on both the upstream and downstream sides of the pipe 101.

[0044] [Embodiment 2] Next, a thermal flow meter according to a second embodiment of the present invention will be described with reference to Fig. 5. This thermal flow meter includes a pipe 101, a temperature adjustment unit 102, a reference temperature measurement unit 103, a sensor circuit 104, a first valve 105a, a second valve 105b, a first circuit 106, diffusion temperature measurement units 107a, 107b, and 107c, a second circuit 108, a third circuit 109, a fourth circuit 110, a fifth circuit 111, a sixth circuit 112, a seventh circuit 113, and an eighth circuit 114.

[0045] The above-described configuration is the same as that of the above-described embodiment 1. In embodiment 2, a ninth circuit 115 is provided that receives information that the fluid has been changed and starts the operation of the first circuit 106. For example, the ninth circuit 115 is connected to a network that houses a higher-level control device (controller) that controls each manufacturing device of the manufacturing process in which the piping 101 is installed. When information about a change in the type of fluid transported using the piping 101 due to a process change or the like is output from the control device via the network, this information is received by the ninth circuit 115.

[0046] When the ninth circuit 115 receives a change in the type of fluid flowing through the pipe 101 in this way, the ninth circuit 115 starts the operation of the first circuit 106. When the first circuit 106 starts operating, the operation of the correction units, which are the first circuit 106, second circuit 108, third circuit 109, fourth circuit 110, fifth circuit 111, sixth circuit 112, and seventh circuit 113, described above, starts.

[0047] An example of the operation of the thermal flow meter according to the second embodiment will be described with reference to the flowchart of FIG.

[0048] First, in a first' step S121, the first circuit 106 stops the flow of fluid to the fluid stopping section using the first valve 105a and the second valve 105b, and then starts driving the temperature adjustment unit 102. Next, in a second' step S122, the second circuit 108 starts driving the temperature adjustment unit 102, and then causes the temperature adjustment unit 102 to perform temperature control.

[0049] Next, in the third step S123, in each of the multiple temperature controls by the temperature control unit 102 in the second step S122, the third circuit 109 calculates the difference between the temperature measurement value of the temperature control unit 102 measured by the diffusion temperature measurement unit, which is different from the temperature measurement value of the temperature control unit 102, and the temperature of the temperature control unit 102, calculates the power consumption of the temperature control unit 102 at the time the temperature difference is calculated, and calculates the thermal conductivity of the fluid from the temperature difference, the power consumption, the distance between the diffusion temperature measurement unit that measured the temperature measurement value and the temperature control unit 102, and the cross-sectional area of ​​the piping 101.

[0050] Next, in step 4' S124, it is determined whether or not the temperature control of the temperature adjustment unit 102 has been performed for all set temperature values. For example, if the temperature control is set to be performed for fluid temperature a measured by the reference temperature measurement unit 103 and for this fluid temperature a, at three temperatures a+10°C, a+20°C, and a+30°C, once the thermal conductivity has been calculated for all of these temperatures (no in step 4' S124), the process proceeds to step 5' S125.

[0051] In step S125, the sixth circuit 112 determines the temperature characteristics of the thermal conductivity of the fluid from the thermal conductivities determined as described above. After that, in step S126, the first valve 105a and the second valve 105b are fully opened to establish a steady state in which the fluid flows.

[0052] Next, in the seventh step S127, the sensor circuit 104 is operated to obtain a sensor value, the seventh circuit 113 obtains a correction value by correcting the sensor value output from the sensor circuit 104 using the temperature characteristics of the thermal conductivity of the obtained fluid, and the eighth circuit 114 calculates the flow rate of the fluid using the obtained correction value.

[0053] Next, in an eighth' step S128, the ninth circuit 115 determines whether or not there is information that the fluid has been changed. If the ninth circuit 115 receives information that the fluid has been changed (yes in the eighth' step S128), the process returns to the first step S121. On the other hand, if the ninth circuit 115 does not receive information that the fluid has been changed, the process returns to a ninth' step S129 in which it determines whether or not the thermal flow meter has received an instruction to stop operation. If an instruction to stop operation has not been received (no in the ninth' step S129), the process returns to the eighth' step S128 in which it determines whether or not there has been information that the fluid has been changed.

[0054] As shown in FIG. 7, the sensor circuit 104, first circuit 106, second circuit 108, third circuit 109, fourth circuit 110, fifth circuit 111, sixth circuit 112, seventh circuit 113, and eighth circuit 114 of the thermal flow meter according to the above-described embodiment may be implemented as a computer device including a CPU (Central Processing Unit) 301, a main memory device 302, an external memory device 303, and a network connection device 304. The CPU 301 operates (executes) a program loaded in the main memory device 302, thereby realizing the above-described functions (correction methods). The program is a program for causing a computer to execute the correction method described in the above-described embodiment. The network connection device 304 is connected to a network 305. The functions may also be distributed among multiple computer devices.

[0055] The thermal flowmeter according to the above-described embodiment can also be configured using a programmable logic device (PLD) such as an FPGA (field-programmable gate array). For example, the logic elements of the FPGA can be provided with a sensor circuit 104, a first circuit 106, a second circuit 108, a third circuit 109, a fourth circuit 110, a fifth circuit 111, a sixth circuit 112, a seventh circuit 113, and an eighth circuit 114 to function as a thermal flowmeter. Each of these can be written into the FPGA by connecting a predetermined writing device. Furthermore, each of the above circuits written into the FPGA can be confirmed by the writing device connected to the FPGA.

[0056] As described above, according to the present invention, the thermal conductivity of the fluid transported through the piping is determined by measuring the temperature of the fluid at a position affected by the temperature of the temperature control unit using diffusion temperature measurement units arranged at multiple locations, so that the flow rate can be measured more accurately even if the fluid to be measured is unknown.

[0057] Some or all of the above-described embodiments may also be described as, but are not limited to, the following supplementary notes.

[0058] [Appendix 1] a temperature control unit configured to heat or cool the fluid in a measurement region of the pipe; a sensor circuit configured to output a sensor value corresponding to a state of thermal diffusion in the fluid heated by the temperature control unit when the temperature control unit is driven so that a difference between a reference temperature and the temperature of the temperature control unit becomes a set temperature difference; a fluid stopping unit configured to stop the flow of the fluid; a first circuit configured to cause the fluid stopping unit to stop the flow of the fluid and then start driving the temperature control unit; diffusion temperature measurement units arranged at a plurality of locations away from the temperature control unit in the axial direction of the pipe, the diffusion temperature measurement units measuring the temperature of the fluid at positions affected by the temperature control unit when the fluid stopping unit has stopped the flow of the fluid; a second circuit configured to cause the temperature control unit to perform a plurality of temperature controls after the temperature control unit has started to drive; a fourth circuit configured to calculate the power consumption of the temperature adjustment unit at the time when the third circuit calculated the temperature difference in each of a plurality of temperature controls by the temperature adjustment unit using the second circuit; a fifth circuit configured to calculate the thermal conductivity of the fluid for each of the temperature differences calculated by the fourth circuit from the temperature difference calculated by the third circuit, the power consumption calculated by the fourth circuit, the distance between the diffusion temperature measurement unit that measured the temperature measurement value and the temperature adjustment unit, and the cross-sectional area of ​​the piping; a sixth circuit configured to calculate the temperature characteristics of the thermal conductivity of the fluid from each of the thermal conductivities calculated by the fifth circuit; a seventh circuit configured to calculate a correction value by correcting the sensor value using the temperature characteristics of the thermal conductivity of the fluid calculated by the sixth circuit; and an eighth circuit configured to calculate the flow rate of the fluid from the correction value.

[0059] [Appendix 2] In the thermal flow meter described in Appendix 1, the sensor circuit outputs the power of the temperature adjustment unit as the sensor value when the temperature adjustment unit is driven so that the difference between the temperature of the temperature adjustment unit and the reference temperature becomes the set temperature difference.

[0060] [Appendix 3] The thermal flow meter according to Supplementary Note 1 includes a first fluid temperature measuring unit that measures a first temperature of the fluid at a position upstream of the temperature adjustment unit that is subject to the thermal influence of the temperature adjustment unit, and a second fluid temperature measuring unit that measures a second temperature of the fluid at a position downstream of the temperature adjustment unit that is subject to the thermal influence of the temperature adjustment unit, wherein at least one of the first fluid temperature measuring unit and the second fluid temperature measuring unit is the diffusion temperature measuring unit adjacent to the temperature adjustment unit, and the sensor circuit outputs, as the sensor value, the temperature difference between the first temperature and the second temperature when the temperature adjustment unit is driven so that the difference between the temperature of the temperature adjustment unit and the reference temperature becomes the set temperature difference.

[0061] [Appendix 4] A thermal flow meter as described in any one of appendices 1 to 3, comprising a reference temperature measurement unit that measures, as the reference temperature, the temperature of the fluid at a reference temperature measurement position upstream of the temperature adjustment unit and not affected by the heat of the temperature adjustment unit.

[0062] [Appendix 5] The thermal flow meter according to any one of Supplementary Notes 1 to 4, further comprising a ninth circuit that receives information that the fluid has been changed and starts operation of the first circuit.

[0063] [Appendix 6] A correction method for correcting a sensor value corresponding to a state of thermal diffusion in a fluid heated by a temperature control unit when the temperature control unit is driven so that a difference between a temperature of the temperature control unit that heats or cools the fluid in a measurement region of a pipe that transports the fluid to be measured and a reference temperature becomes a set temperature difference, the method comprising: a first step of stopping the flow of the fluid and then starting to drive the temperature control unit; a second step of causing the temperature control unit to perform a plurality of temperature controls after starting to drive the temperature control unit; and a third step of calculating a difference between a temperature measurement value different from that of the temperature control unit measured by diffusion temperature measurement units that are arranged at a plurality of locations away from the temperature control unit in the axial direction of the pipe and that measure temperatures of the fluid at positions affected by the temperature control unit and that are affected by the temperature control unit, in each of the plurality of temperature controls by the temperature control unit in the second step. a fourth step of determining the power consumption of the temperature control unit at the time the temperature difference was determined in the third step, for each of a plurality of temperature controls by the temperature control unit in the second step; a fifth step of determining the thermal conductivity of the fluid for each of the temperature differences determined in the fourth step from the temperature difference determined in the third step, the power consumption determined in the fourth step, the distance between the diffusion temperature measurement unit that measured the temperature measurement value and the temperature control unit, and the cross-sectional area of ​​the piping; a sixth step of determining the temperature characteristics of the thermal conductivity of the fluid from each of the thermal conductivities determined in the fifth step; a seventh step of determining the sensor value; an eighth step of determining a correction value by correcting the sensor value using the temperature characteristics of the thermal conductivity of the fluid determined in the sixth step; and a ninth step of calculating the flow rate of the fluid from the correction value.

[0064] [Appendix 7] In the correction method described in Appendix 6, the seventh step is a correction method in which the power of the temperature adjustment unit when the temperature adjustment unit is driven so that the difference between the temperature of the temperature adjustment unit and the reference temperature becomes the set temperature difference is used as the sensor value.

[0065] [Appendix 8] In the correction method described in Supplementary Note 6, the seventh step is a correction method in which the sensor value is the temperature difference between a first temperature of the fluid measured at a position upstream of the temperature adjustment unit that is affected by the heat of the temperature adjustment unit, and a second temperature of the fluid measured at a position downstream of the temperature adjustment unit that is affected by the heat of the temperature adjustment unit, when the temperature adjustment unit is driven so that the difference between the temperature of the temperature adjustment unit and the reference temperature becomes the set temperature difference.

[0066] [Appendix 9] In the correction method described in Appendix 7 or 8, the seventh step is a correction method in which the temperature of the fluid is measured at a reference temperature measurement position upstream of the temperature adjustment unit and not affected by the heat of the temperature adjustment unit, and the measured temperature is used as the reference temperature.

[0067] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention. [Explanation of symbols]

[0068] 101...piping, 102...temperature control unit, 103...fluid temperature measurement unit, 104...sensor circuit, 105a...first valve, 105b...second valve, 106...first circuit, 107a, 107b, 107c...diffusion temperature measurement unit, 108...second circuit, 109...third circuit, 110...fourth circuit, 111...fifth circuit, 112...sixth circuit, 113...seventh circuit, 114...eighth circuit.

Claims

1. A pipe for transporting a fluid to be measured; a temperature control unit configured to heat or cool the fluid in a measurement region of the pipe; a sensor circuit configured to output a sensor value corresponding to a state of thermal diffusion in the fluid heated by the temperature adjustment unit when the temperature adjustment unit is driven so that a difference between a reference temperature and the temperature of the temperature adjustment unit becomes a set temperature difference; a fluid stop configured to stop the flow of the fluid; a first circuit configured to stop the flow of the fluid with the fluid stopping unit and then start driving the temperature adjustment unit; a diffusion temperature measuring unit arranged at a plurality of locations apart from the temperature adjusting unit in the axial direction of the piping, the diffusion temperature measuring unit measuring the temperature of the fluid at a location affected by the temperature adjusting unit when the fluid stopping unit stops the flow of the fluid; a second circuit configured to cause the temperature adjustment unit to perform a plurality of temperature controls after the temperature adjustment unit starts operating; a third circuit configured to calculate a difference between a temperature measured by the diffusion temperature measurement unit, which is different from the temperature of the temperature adjustment unit, and the temperature of the temperature adjustment unit, in each of a plurality of temperature controls by the temperature adjustment unit using the second circuit; a fourth circuit configured to calculate the power consumption of the temperature adjustment unit at a time when the third circuit calculates a temperature difference in each of a plurality of temperature controls by the temperature adjustment unit using the second circuit; a fifth circuit configured to calculate the thermal conductivity of the fluid for each temperature difference calculated by the fourth circuit from the temperature difference calculated by the third circuit, the power consumption calculated by the fourth circuit, the distance between the diffusion temperature measurement unit that measured the temperature value and the temperature adjustment unit, and the cross-sectional area of ​​the pipe; a sixth circuit configured to determine the temperature characteristics of the thermal conductivity of the fluid from the thermal conductivities determined by the fifth circuit; a seventh circuit configured to calculate a correction value obtained by correcting the sensor value using the temperature characteristic of the thermal conductivity of the fluid calculated by the sixth circuit; and an eighth circuit configured to calculate a flow rate of the fluid from the correction value; A thermal flow meter comprising:

2. 2. The thermal flow meter according to claim 1, The sensor circuit is a thermal flow meter that outputs the power of the temperature control unit as the sensor value when the temperature control unit is driven so that the difference between the temperature of the temperature control unit and the reference temperature becomes the set temperature difference.

3. 2. The thermal flow meter according to claim 1, a first fluid temperature measuring unit that measures a first temperature of the fluid at a position upstream of the temperature adjusting unit and that is subject to thermal influence from the temperature adjusting unit; a second fluid temperature measuring unit that measures a second temperature of the fluid at a position downstream of the temperature adjusting unit and that is subjected to a thermal effect from the temperature adjusting unit; Equipped with At least one of the first fluid temperature measuring unit and the second fluid temperature measuring unit is the diffusion temperature measuring unit adjacent to the temperature adjustment unit, The sensor circuit outputs, as the sensor value, a temperature difference between the first temperature and the second temperature when the temperature adjustment unit is driven so that a difference between the temperature of the temperature adjustment unit and the reference temperature becomes the set temperature difference. Thermal flow meter.

4. The thermal flow meter according to any one of claims 1 to 3, a thermal flow meter including a reference temperature measurement unit that measures, as the reference temperature, the temperature of the fluid at a reference temperature measurement position that is upstream of the temperature adjustment unit and is not affected by the heat of the temperature adjustment unit;

5. The thermal flow meter according to any one of claims 1 to 3, The thermal flow meter further includes a ninth circuit that receives information that the fluid has been changed and starts operation of the first circuit.

6. 1. A method for correcting a sensor value corresponding to a state of thermal diffusion in a fluid heated by a temperature control unit, when the temperature control unit is driven so that a difference between a temperature of the temperature control unit that heats or cools a fluid in a measurement region of a pipe that transports the fluid to be measured and a reference temperature becomes a set temperature difference, the method comprising: a first step of stopping the flow of the fluid and then starting to drive the temperature adjustment unit; a second step of causing the temperature adjustment unit to perform a plurality of temperature controls after the temperature adjustment unit starts to operate; a third step of calculating a difference between a temperature measured by the temperature control unit and a temperature measured by a diffusion temperature measurement unit, the diffusion temperature measurement unit being arranged at a plurality of locations away from the temperature control unit in the axial direction of the piping and measuring the temperature of the fluid at a position affected by the temperature of the temperature control unit, and the temperature measured by the temperature control unit; a fourth step of calculating power consumption of the temperature adjustment unit at a time when the temperature difference is calculated in the third step, in each of the plurality of temperature controls by the temperature adjustment unit in the second step; a fifth step of calculating the thermal conductivity of the fluid for each of the temperature differences calculated in the fourth step from the temperature difference calculated in the third step, the power consumption calculated in the fourth step, the distance between the diffusion temperature measurement unit that measured the temperature value and the temperature control unit, and the cross-sectional area of ​​the pipe; a sixth step of determining the temperature characteristics of the thermal conductivity of the fluid from the respective thermal conductivities determined in the fifth step; a seventh step of determining the sensor value; an eighth step of calculating a corrected value by correcting the sensor value using the temperature characteristic of the thermal conductivity of the fluid calculated in the sixth step; a ninth step of calculating a flow rate of the fluid from the correction value; A correction method comprising:

7. 7. The correction method according to claim 6, The seventh step is a correction method in which the power of the temperature adjustment unit when the temperature adjustment unit is driven so that the difference between the temperature of the temperature adjustment unit and the reference temperature becomes the set temperature difference, is set as the sensor value.

8. 7. The correction method according to claim 6, The seventh step is a correction method in which the sensor value is the temperature difference between a first temperature of the fluid measured at a position upstream of the temperature control unit that is subject to the thermal influence of the temperature control unit, and a second temperature of the fluid measured at a position downstream of the temperature control unit that is subject to the thermal influence of the temperature control unit, when the temperature control unit is driven so that the difference between the temperature of the temperature control unit and the reference temperature becomes the set temperature difference.

9. 9. The correction method according to claim 7 or 8, The seventh step is a correction method in which the temperature of the fluid is measured at a reference temperature measurement position upstream of the temperature adjustment unit and not affected by the heat of the temperature adjustment unit, and the measured temperature is used as the reference temperature.

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