A thermocouple temperature measurement system calibration method

Abstract

This invention aims to provide a simple, efficient, and low-cost method for calibrating a thermocouple temperature measurement system with high precision. The invention includes the following specific steps: Step S1, connecting the thermocouple wires of the thermocouple temperature measurement system to a constant temperature water tank; Step S2, setting up a high-precision temperature measuring instrument; Step S3, setting the test temperature value and adjusting the test environment to a stable state; Step S4, collecting data after the temperature stabilizes; Step S5, setting two different sets of data and repeating steps S3 and S4 to obtain data sets; Step S6, fitting a straight line to the data sets using the least squares method to obtain calibration parameters and writing them into the thermocouple temperature measurement system; Step S7, setting a verification temperature and testing to obtain a verification data set; Step S8, calculating the water temperature difference based on the verification data set and judging the calculation result. This invention is applied to the technical field of temperature testing and calibration.

Description

Technical Field

[0001] This invention applies to the technical field of temperature testing and calibration, and particularly relates to a calibration method for a thermocouple temperature measurement system. Background Technology

[0002] As consumer electronics become increasingly powerful and demanding in terms of performance, higher requirements are being placed on thermal management testing. Typically, temperature measurement systems are calibrated using simulated heating and heat sinks based on the product's thermal requirements. Temperature data is collected at different locations on the heat sink to determine its performance.

[0003] Because high-precision temperature measuring instruments are expensive and their detection methods are not compatible with those used for heat sink monitoring, thermocouple temperature measurement is primarily used to collect heat sink temperatures. However, the accuracy of thermocouple temperature measurement is affected by various factors, including cold junction compensation accuracy, wire material consistency, and signal conditioning circuit accuracy. Therefore, the thermocouple temperature measurement system needs to be calibrated when using thermocouple temperature measurement.

[0004] Conventional thermocouple temperature calibration methods include the fixed-point method, which involves inserting a standard thermocouple and the thermocouple to be calibrated into a fixed-point furnace. Calibration is performed when a temperature plateau is formed during a phase transition. However, this method requires extremely expensive and complex equipment and is cumbersome to operate. Another method is the on-site / online rapid comparison method, which compares the thermocouple to be calibrated with a built-in or external high-precision temperature measuring instrument. These high-precision instruments are typically high-precision process calibrators or platinum resistance thermometers. This method is limited by the uniformity and stability of the temperature field in a dry-block furnace, resulting in lower accuracy.

[0005] Therefore, there is a need for a simple, efficient, and low-cost method for calibrating thermocouple temperature measurement systems that can achieve high precision. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a simple, efficient and low-cost method for calibrating a thermocouple temperature measurement system that can achieve high precision.

[0007] The technical solution adopted in this invention is as follows: This invention includes the following specific steps. Step S1: Place and fix several thermocouple wires of the thermocouple temperature measurement system in a constant temperature water tank, so that the several thermocouple wires are in full contact with the water in the constant temperature water tank. Step S2: Distribute the temperature probes of the high-precision thermometer evenly on both sides of the constant temperature water tank. Step S3: Set the temperature of the constant temperature water tank to Tc1, and collect the temperature difference between the two sides of the constant temperature water tank using the high-precision thermometer; Step S4: When the temperature difference between the two sides of the constant temperature water tank is less than 0.02℃, and the average temperature measured by the high-precision thermometer is within the range of Tc1±0.1, the thermocouple temperature measurement system and the high-precision thermometer start collecting temperature data, and record the collected temperature data as T1, T2...T100 and F1, F2...F100 respectively. Step S5: Set the temperature of the constant temperature water tank to Tc2 and Tc3 in sequence, and repeat the process of steps S3 and S4 to obtain temperature data T101, T102...T200, T201, T202...T300, F101, F102...F200, F201, F202...F300; Step S5: Fit the data set X=(T1,T2,…,T300) and Y=(F1,F2,…,F300) to a straight line Y=kX+b using the least squares method, obtain the values ​​of parameters k and b, and write them into the thermocouple temperature measurement system; Step S6: Set the temperature of the constant temperature water tank to Tc4 and Tc5 in sequence. When the temperature difference between the two sides of the constant temperature water tank is less than 0.02℃, the thermocouple temperature measurement system and the high-precision temperature measuring instrument are turned on to collect temperature data, and obtain T301, T302...T400, T401, T402...T500, F301, F302...F400, F401, F402...F500 respectively. Step S7: Calculate the water temperature difference value Error measured by the thermocouple temperature measurement system and the high-precision temperature measuring instrument based on the data obtained in step S6. When the water temperature difference value Error is less than 0.05℃, the calibration is successful; otherwise, repeat steps S3 to S6 until the water temperature difference value Error is less than 0.05℃.

[0008] As can be seen from the above scheme, a constant-temperature water tank provides a stable and reliable testing environment. Simultaneously, a high-precision thermometer performs two-channel data acquisition, collecting temperature data from both sides of the constant-temperature water tank as the calibration basis. Using 300 continuously collected data sets as the fitting basis, a straight line is fitted, and the values ​​of calibration parameters k and b are obtained. Simultaneously, data is collected from the thermocouple temperature measurement system after the calibration parameters are written, obtaining the temperature difference between the calibrated data and the water temperature measured by the high-precision thermometer. The calibration is verified by comparing the water temperature difference. This achieves rapid calibration and verification of the thermocouple temperature measurement system, ensuring that the detection accuracy of the thermocouple temperature measurement system meets the testing requirements.

[0009] A preferred solution is one where the parameters k and b satisfy: , , where n=300, Xi=Ti, Yi=Fi.

[0010] A preferred embodiment is that the water temperature difference value Error satisfies , where m=301, 302……500.

[0011] In a preferred embodiment, the thermocouple temperature measurement system includes a multiplexer and an analog-to-digital converter. The output of the multiplexer is connected to the input of the analog-to-digital converter, and several inputs of the multiplexer are connected to thermocouples. Each group of thermocouples is connected to cold junction compensation. Attached Figure Description

[0012] Figure 1 This is a flowchart of the present invention; Figure 2 This is a schematic diagram of the thermocouple temperature measurement system. Figure 3 This is a temperature data distribution diagram of the calibrated thermocouple temperature measurement system. Detailed Implementation

[0013] like Figure 1 As shown, in this embodiment, the present invention includes the following specific steps: Step S1: Place and fix several thermocouple wires of the thermocouple temperature measurement system in a constant temperature water tank to prevent the thermocouple wires from swinging inside the water tank, while ensuring that the thermocouple wires are in full contact with the water in the constant temperature water tank; wherein, the constant temperature water tank is a Fluke 7008 constant temperature water bath from Fluke Corporation. Step S2: Distribute the temperature probes of the two channels of the high-precision thermometer evenly on both sides of the constant temperature water tank. The high-precision thermometer is a Fluke 1524 high-precision two-channel thermometer from Fluke Corporation. Step S3: Set the temperature of the constant temperature water tank to Tc1, and collect the temperature difference between the two sides of the constant temperature water tank using the high-precision thermometer; Step S4: When the temperature difference between the two sides of the constant temperature water tank is less than 0.02℃, and the average temperature measured by the high-precision thermometer is within the range of Tc1±0.1, the thermocouple temperature measurement system and the high-precision thermometer start collecting temperature data, and record the collected temperature data as T1, T2...T100 and F1, F2...F100 respectively; the high-precision thermometer collects the temperature data on both sides of the constant temperature water tank, and then judges the temperature state of the constant temperature water tank by the temperature difference. At the same time, it compares the average temperature with the set temperature Tc1 to ensure the accuracy of the test environment temperature and ensure the reliability of the calibration data acquisition. Step S5: Set the temperature of the constant temperature water tank to Tc2 and Tc3 sequentially, and repeat the process of steps S3 and S4 to obtain temperature data T101, T102...T200, T201, T202...T300, F101, F102...F200, F201, F202...F300; By setting different test temperatures and collecting multiple sets of data, the reliability of the calibration parameters is ensured. Step S5: Fit the data set X=(T1,T2,…,T300) and Y=(F1,F2,…,F300) to a straight line Y=kX+b using the least squares method, obtain the values ​​of parameters k and b, and write them into the thermocouple temperature measurement system; parameters k and b satisfy: , Where n=300, Xi=Ti, Yi=Fi, and Ti and Fi correspond to the data values ​​in the data set; Step S6: Set the temperature of the constant temperature water tank to Tc4 and Tc5 in sequence. When the temperature difference between the two sides of the constant temperature water tank is less than 0.02℃, the thermocouple temperature measurement system and the high-precision temperature measuring instrument are turned on to collect temperature data, and obtain T301, T302...T400, T401, T402...T500, F301, F302...F400, F401, F402...F500 respectively. Step S7: Calculate the water temperature difference value Error measured by the thermocouple temperature measurement system and the high-precision thermometer based on the data obtained in step S6. If the water temperature difference value Error is less than 0.05℃, the calibration is successful; otherwise, repeat steps S3 to S6 until the water temperature difference value Error is less than 0.05℃. Wherein, the water temperature difference value Error satisfies... , where m=301, 302……500.

[0014] like Figure 3 As shown, the temperature measured by the calibrated thermocouple temperature measurement system has an error of less than 0.05℃ compared with the temperature measured by the standard temperature measurement device.

[0015] like Figure 2As shown, in this embodiment, the thermocouple temperature measurement system includes a multiplexer and an analog-to-digital converter (ADC). The output of the multiplexer is connected to the input of the ADC, and several inputs of the multiplexer are connected to thermocouples. Each group of thermocouples is connected to cold junction compensation. A thermocouple is a temperature sensor that generates a voltage that changes with temperature. A thermocouple consists of two leads made of different metals, welded together to form a junction. As the temperature changes from the junction to the ends of the leads, a small voltage is generated at the junction. This small voltage is amplified by an amplifier and then converted into a digital signal by the ADC. The acquired voltage is then inversely converted, and the temperature can be calculated from the thermocouple voltage using an inverse polynomial function. The multiplexer enables multi-channel thermocouple temperature measurement. Since the voltage output by the thermocouple reflects the temperature difference between the measuring junction (hot junction) and the reference junction (cold junction), the voltage generated by the thermocouple is non-linear and depends specifically on the temperature of the cold junction. By setting cold junction compensation for data acquisition, the thermocouple junction temperature can be accurately determined. During testing, both the thermocouple temperature measurement system and the high-precision temperature measuring instrument are connected to the host computer for data recording.

[0016] Although the embodiments of the present invention are described with reference to actual solutions, they do not constitute a limitation on the meaning of the present invention. Modifications to the embodiments and combinations with other solutions based on this specification will be obvious to those skilled in the art.

Claims

1. A calibration method for a thermocouple temperature measurement system, characterized in that, It includes the following specific steps: Step S1: Place and fix several thermocouple wires of the thermocouple temperature measurement system in a constant temperature water tank, so that the several thermocouple wires are in full contact with the water in the constant temperature water tank. Step S2: Distribute the temperature probes of the high-precision thermometer evenly on both sides of the constant temperature water tank. Step S3: Set the temperature of the constant temperature water tank to Tc1, and collect the temperature difference between the two sides of the constant temperature water tank using the high-precision thermometer; Step S4: When the temperature difference between the two sides of the constant temperature water tank is less than 0.02℃, and the average temperature measured by the high-precision thermometer is within the range of Tc1±0.1, the thermocouple temperature measurement system and the high-precision thermometer start collecting temperature data, and record the collected temperature data as T1, T2...T100 and F1, F2...F100 respectively. Step S5: Set the temperature of the constant temperature water tank to Tc2 and Tc3 in sequence, and repeat the process of steps S3 and S4 to obtain temperature data T101, T102...T200, T201, T202...T300, F101, F102...F200, F201, F202...F300; Step S5: Fit the data set X=(T1,T2,…,T300) and Y=(F1,F2,…,F300) to a straight line Y=kX+b using the least squares method, obtain the values ​​of parameters k and b, and write them into the thermocouple temperature measurement system; Step S6: Set the temperature of the constant temperature water tank to Tc4 and Tc5 in sequence. When the temperature difference between the two sides of the constant temperature water tank is less than 0.02℃, the thermocouple temperature measurement system and the high-precision temperature measuring instrument are turned on to collect temperature data, and obtain T301, T302...T400, T401, T402...T500, F301, F302...F400, F401, F402...F500 respectively. Step S7: Calculate the water temperature difference value Error measured by the thermocouple temperature measurement system and the high-precision temperature measuring instrument based on the data obtained in step S6. When the water temperature difference value Error is less than 0.05℃, the calibration is successful; otherwise, repeat steps S3 to S6 until the water temperature difference value Error is less than 0.05℃.

2. The calibration method for a thermocouple temperature measurement system according to claim 1, characterized in that, Parameters k and b satisfy: , , where n=300, Xi=Ti, Yi=Fi.

3. The calibration method for a thermocouple temperature measurement system according to claim 1, characterized in that: The water temperature difference value Error satisfies , where m=301, 302……500.

4. The calibration method for a thermocouple temperature measurement system according to claim 1, characterized in that: The thermocouple temperature measurement system includes a multiplexer and an analog-to-digital converter. The output of the multiplexer is connected to the input of the analog-to-digital converter. Several inputs of the multiplexer are connected to thermocouples, and each group of thermocouples is connected to cold junction compensation.

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