Thermocouple thermoelectromotive force detection method

Abstract

A thermocouple thermoelectromotive force detection method comprises the following steps: 1) clamping a test sample, placing a hot end of a thermocouple to be detected and a standard platinum resistance thermometer in a refrigeration thermostatic bath, connecting a cold end of the thermocouple to be detected with a copper wire, and placing the cold end of the thermocouple to be detected and another standard platinum resistance thermometer in a zero-degree thermostat; (2) the detection temperature is controlled, and the measurement temperature of the refrigeration thermostatic bath and the measurement temperature of the zero-degree thermostat are set respectively; 3) acquisition of detection data: after the temperatures of the refrigeration thermostatic bath and the zero-degree thermostat are stable, rapidly acquiring data of the standard platinum resistance thermometer and the detected thermocouple; 4) data processing: processing the collected detection data; and 5) result judgment. The temperature of the cold end and the hot end of the thermocouple is accurately controlled through the detection equipment, the measurement precision of the thermoelectromotive force of the thermocouple is greatly improved, and high-precision thermoelectromotive force measurement of the thermocouple within the temperature range of 0-100 DEG C and the temperature allowance of + / -0.05 DEG C is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of thermocouple testing, and in particular to a method for detecting thermoelectromotive force of a thermocouple. Background Art

[0002] In the industrial production process, thermocouples are widely used in the field of temperature measurement due to their simple structure, high accuracy and wide measurement range. Thermoelectric potential is the core parameter of thermocouples. The accurate measurement of thermoelectric potential not only reflects the accuracy level of a thermocouple, but also is an important basis for the application of thermocouples in production.

[0003] In recent years, the research and development and production of high-precision thermocouples have increased, especially in the field of aerospace industry, where the tolerance requirement for thermocouples in the temperature range of 0 to 100 ° C has reached ± 0.05 ° C. This is not only an important topic for the research and development of high-precision thermocouples, but also puts forward more specific requirements for high-precision thermoelectric potential measurement. The national standard GB / T16839.1-2018 stipulates that the tolerance of Class 1 T-type thermocouples in the temperature range of -40 to 350 ° C is ± 0.5 ° C, which is the minimum parameter value of the temperature tolerance in the current thermocouple standard in my country. For this temperature range, the measurement uncertainty provided by most thermocouple calibration agencies is not less than 0.2 ° C. Therefore, there is still a considerable gap between the current thermocouple measurement method and the measurement requirements of high-precision thermocouples. Summary of the invention

[0004] The purpose of the present invention is to provide a method for detecting thermocouple thermoelectromotive force in view of the corresponding deficiencies of the prior art. This method greatly improves the measurement accuracy of thermocouple thermoelectromotive force, and achieves a temperature tolerance of ±0.05°C in the temperature range of 0 to 100°C, which can meet the needs of high-precision thermocouple thermoelectromotive force measurement.

[0005] The object of the present invention is to adopt the following scheme to achieve: a method for detecting thermocouple thermoelectromotive force, comprising the following steps:

[0006] 1) Clamp the test sample, put the hot end of the thermocouple to be tested and the standard platinum resistance thermometer into a test tube 1 filled with liquid medium, so that the hot end of the thermocouple to be tested and the probe of the standard platinum resistance thermometer are in the same position, then place the test tube 1 in a refrigeration thermostat, connect the cold end of the thermocouple to be tested with a copper wire and put it into another test tube 2 filled with liquid medium together with another standard platinum resistance thermometer, so that the cold end of the thermocouple to be tested and the probe of the standard platinum resistance thermometer are in the same position, and then place the test tube 2 in a zero-degree thermostat;

[0007] 2) Control the detection temperature, set the measurement temperature of the refrigeration thermostat and the zero-degree thermostat respectively, so that the temperature of the refrigeration thermostat and the zero-degree thermostat is in a real-time monitoring state;

[0008] 3) Data collection: After the temperature of the refrigeration thermostat and the zero-degree thermostat is stable, when the temperature change value of the standard platinum resistance thermometer is less than 0.005°C / min, quickly collect data from the standard platinum resistance thermometer and the thermocouple being tested, and collect data back and forth multiple times, and take the average value as the test result;

[0009] 4) Data processing: the actual temperature t of the refrigeration thermostat and the zero-degree thermostat is calculated using the formula based on the average value of the collected standard platinum resistance thermometer and the measured thermocouple. 实 , the temperature difference Δt between the actual temperature and the set temperature, the thermoelectric potential value e of the measured thermocouple at the set temperature 被t and the experimental standard deviation of repeated measurements of the thermocouple being tested;

[0010] 5) Result judgment: compare the calculated experimental standard deviation of repeated measurements of the tested thermocouple with the tolerance requirements of the thermocouple.

[0011] In step 1), the liquid medium contained in test tube 1 is antifreeze, and the liquid medium contained in test tube 2 is alcohol.

[0012] In step 1), test tube 1 is placed in a refrigerated thermostatic bath at a depth of 300 to 400 mm, and test tube 2 is placed in a zero-degree thermostat at a depth of 150 to 200 mm.

[0013] In step 2), the temperatures of the refrigeration thermostat and the zero-degree thermostat are under real-time monitoring by a standard platinum resistance thermometer.

[0014] The actual temperature of the cooling thermostat and the zero-degree thermostat in step 4) is t 实 By formula Calculated, where is the average acquisition value of the standard platinum resistance thermometer in the refrigeration thermostat and the zero-degree thermostat, R 标证 is the resistance value corresponding to the calibration temperature point on the standard platinum resistance thermometer certificate, (dR / dt) 标t It is the rate of change of resistance of a standard platinum resistance thermometer at a certain measuring temperature to temperature, which can be obtained by querying the corresponding measurement certificate.

[0015] In step 4), the temperature difference Δt between the actual temperature and the set temperature is calculated by the formula Δt=t 实 -t 设 Calculated, where t 设 is the set temperature value of the refrigeration thermostat and the zero-degree thermostat, t 实 is the actual temperature of the refrigeration thermostat and the zero-degree thermostat.

[0016] The thermoelectric potential value e of the thermocouple under test at the set temperature in step 4) 被t By formula Calculated, where is the average acquisition value of the measured thermocouple, Δt 总 is the sum of the temperature differences between the refrigeration thermostat and the zero-degree thermostat, S 被t It is the differential thermoelectromotive force of the measured thermocouple at a certain measuring temperature, which can be obtained by consulting the corresponding national standard.

[0017] The experimental standard deviation of repeated measurements of the thermocouple under test in step 4) is calculated by the Bessel formula Calculated, where n is the number of measurements, x i is the measured value of the ith measurement, is the arithmetic mean of n measurements.

[0018] The advantage of the present invention is that the present invention accurately controls the temperature of the hot and cold ends of the thermocouple through the detection equipment, and the detection range is 0-100°C, which greatly improves the measurement accuracy of the thermocouple thermoelectric potential, and the temperature tolerance is ±0.05°C, which can meet the needs of high-precision thermocouple thermoelectric potential measurement. The present invention expands the current measurement accuracy of thermocouple thermoelectric potential in China and provides a basic guarantee for the research and development and production of high-precision thermocouples. DETAILED DESCRIPTION

[0019] A method for detecting thermocouple thermoelectromotive force comprises the following steps:

[0020] 1) Clamp the test sample, put the hot end of the thermocouple to be tested and the standard platinum resistance thermometer into a test tube 1 filled with liquid medium, so that the hot end of the thermocouple to be tested and the probe of the standard platinum resistance thermometer are in the same position, then place the test tube 1 in a refrigeration thermostat, connect the cold end of the thermocouple to be tested with a copper wire and put it into another test tube 2 filled with liquid medium together with another standard platinum resistance thermometer, so that the cold end of the thermocouple to be tested and the probe of the standard platinum resistance thermometer are in the same position, and then place the test tube 2 in a zero-degree thermostat;

[0021] 2) Control the detection temperature, set the measurement temperature of the refrigeration thermostat and the zero-degree thermostat respectively, so that the temperature of the refrigeration thermostat and the zero-degree thermostat is in a real-time monitoring state;

[0022] 3) Data collection: After the temperature of the refrigeration thermostat and the zero-degree thermostat is stable, when the temperature change value of the standard platinum resistance thermometer is less than 0.005°C / min, quickly collect data from the standard platinum resistance thermometer and the thermocouple being tested, and collect data back and forth multiple times, and take the average value as the test result;

[0023] 4) Data processing: the actual temperature t of the refrigeration thermostat and the zero-degree thermostat is calculated using the formula based on the average value of the collected standard platinum resistance thermometer and the measured thermocouple. 实, the temperature difference Δt between the actual temperature and the set temperature, the thermoelectric potential value e of the measured thermocouple at the set temperature 被t and the experimental standard deviation of repeated measurements of the thermocouple being tested;

[0024] 5) Result judgment: compare the calculated experimental standard deviation of repeated measurements of the tested thermocouple with the tolerance requirements of the thermocouple.

[0025] In step 1), the liquid medium contained in test tube 1 is antifreeze, and the liquid medium contained in test tube 2 is alcohol.

[0026] In step 1), test tube 1 is placed in a refrigerated thermostatic bath at a depth of 300 to 400 mm, and test tube 2 is placed in a zero-degree thermostat at a depth of 150 to 200 mm.

[0027] In step 2), the temperatures of the refrigeration thermostat and the zero-degree thermostat are under real-time monitoring by a standard platinum resistance thermometer.

[0028] The actual temperature of the cooling thermostat and the zero-degree thermostat in step 4) is t 实 By formula Calculated, where is the average acquisition value of the standard platinum resistance thermometer in the refrigeration thermostat and the zero-degree thermostat, R 标证 is the resistance value corresponding to the calibration temperature point on the standard platinum resistance thermometer certificate, (dR / dt) 标t It is the rate of change of resistance of a standard platinum resistance thermometer at a certain measuring temperature to temperature, which can be obtained by querying the corresponding measurement certificate.

[0029] In step 4), the temperature difference Δt between the actual temperature and the set temperature is calculated by the formula Δt=t 实 -t 设 Calculated, where t 设 is the set temperature value of the refrigeration thermostat and the zero-degree thermostat, t 实 is the actual temperature of the refrigeration thermostat and the zero-degree thermostat.

[0030] The thermoelectric potential value e of the thermocouple under test at the set temperature in step 4) 被t By formula Calculated, where is the average acquisition value of the measured thermocouple, Δt 总 is the sum of the temperature differences between the refrigeration thermostat and the zero-degree thermostat, S 被t It is the differential thermoelectromotive force of the measured thermocouple at a certain measuring temperature, which can be obtained by consulting the corresponding national standard.

[0031] The experimental standard deviation of repeated measurements of the thermocouple under test in step 4) is calculated by the Bessel formula Calculated, where n is the number of measurements, x i is the measured value of the ith measurement, is the arithmetic mean of n measurements.

[0032] Example 1

[0033] Place the hot end of the thermocouple to be tested and the standard platinum resistance thermometer into a test tube filled with antifreeze, and then insert the test tube into the refrigeration thermostat at a depth of 350mm. After connecting the cold end of the thermocouple to be tested with a copper wire, place it in another test tube filled with alcohol together with another standard platinum resistance thermometer, and then insert the test tube into the zero-degree thermostat at a depth of 200mm. Set the temperature of the refrigeration thermostat to 20℃, the temperature of the zero-degree thermostat to 0℃, and detect the thermoelectric potential of the thermocouple to be tested. When the temperature change value of the standard platinum resistance thermometer is less than 0.005℃ / min, collect the data of the standard platinum resistance thermometer and the thermocouple to be tested. Repeat the measurement three times, and collect four sets of data each time. The collected data are shown in Table 1, and the actual test results of the thermocouple to be tested obtained after data processing are shown in Table 2.

[0034] Table 1 Collection data

[0035]

[0036] Table 2 Data processing results

[0037]

[0038] The actual values ​​of the tested thermocouple measured three times were calculated by Bessel formula, and the experimental standard deviation was 0.07μV, and the converted temperature was 0.011℃. This temperature deviation can meet the requirement of temperature tolerance of ±0.05℃ for thermocouples in the temperature range of 0-100℃.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for detecting thermocouple thermoelectromotive force, characterized in that: The following steps are involved: 1) Clamp the test sample, put the hot end of the thermocouple to be tested and the standard platinum resistance thermometer into a test tube 1 filled with liquid medium, so that the hot end of the thermocouple to be tested and the probe of the standard platinum resistance thermometer are in the same position, then place the test tube 1 in a refrigeration thermostat, connect the cold end of the thermocouple to be tested with a copper wire and put it into another test tube 2 filled with liquid medium together with another standard platinum resistance thermometer, so that the cold end of the thermocouple to be tested and the probe of the standard platinum resistance thermometer are in the same position, and then place the test tube 2 in a zero-degree thermostat; 2) Control the detection temperature, set the measurement temperature of the refrigeration thermostat and the zero-degree thermostat respectively, so that the temperature of the refrigeration thermostat and the zero-degree thermostat is in a real-time monitoring state; 3) Data collection: After the temperature of the refrigeration thermostat and the zero-degree thermostat is stable, when the temperature change value of the standard platinum resistance thermometer is less than 0.005°C / min, quickly collect data from the standard platinum resistance thermometer and the thermocouple being tested, and collect data back and forth multiple times, and take the average value as the test result; 4) Data processing: the actual temperature t of the refrigeration thermostat and the zero-degree thermostat is calculated using the formula based on the average value of the collected standard platinum resistance thermometer and the measured thermocouple. 实 , the temperature difference Δt between the actual temperature and the set temperature, the thermoelectric potential value e of the measured thermocouple at the set temperature 被t and the experimental standard deviation of repeated measurements of the thermocouple being tested; 5) Result judgment: compare the calculated experimental standard deviation of repeated measurements of the tested thermocouple with the tolerance requirements of the thermocouple.

2. The detection method according to claim 1, characterized in that: In step 1), the liquid medium contained in test tube 1 is antifreeze, and the liquid medium contained in test tube 2 is alcohol.

3. The detection method according to claim 1, characterized in that: In step 1), test tube 1 is placed in a refrigerated thermostatic bath at a depth of 300 to 400 mm, and test tube 2 is placed in a zero-degree thermostat at a depth of 150 to 200 mm.

4. The detection method according to claim 1, characterized in that: In step 2), the temperatures of the refrigeration thermostat and the zero-degree thermostat are under real-time monitoring by a standard platinum resistance thermometer.

5. The detection method according to claim 1, characterized in that: The actual temperature of the cooling thermostat and the zero-degree thermostat in step 4) is t 实 By formula Calculated, where is the average acquisition value of the standard platinum resistance thermometer in the refrigeration thermostat and the zero-degree thermostat, R 标证 is the resistance value corresponding to the calibration temperature point on the standard platinum resistance thermometer certificate, (dR / dt) 标t It is the rate of change of resistance of a standard platinum resistance thermometer at a certain measuring temperature.

6. The detection method according to claim 1, characterized in that: In step 4), the temperature difference Δt between the actual temperature and the set temperature is calculated by the formula Δt=t 实 -t 设 Calculated, where t 设 is the set temperature value of the refrigeration thermostat and the zero-degree thermostat, t 实 is the actual temperature of the refrigeration thermostat and the zero-degree thermostat.

7. The detection method according to claim 1, characterized in that: The thermoelectric potential value e of the thermocouple under test at the set temperature in step 4) 被t By formula Calculated, where is the average acquisition value of the measured thermocouple, Δt 总 is the sum of the temperature differences between the refrigeration thermostat and the zero-degree thermostat, S 被t It is the differential thermoelectromotive force of the measured thermocouple at a certain measuring temperature.

8. The detection method according to claim 1, characterized in that: The experimental standard deviation of repeated measurements of the thermocouple under test in step 4) is calculated by the Bessel formula Calculated, where n is the number of measurements, x i is the measured value of the ith measurement, is the arithmetic mean of n measurements.

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