Selection and Verification Method of Temperature Verification Point for PT100 Thermocouple Temperature Sensor
1. For each verification point of Pt100, select 0°C and 100°C, and check the compliance of the actual resistance temperature coefficient a;
2. When △a does not meet the requirements, the temperature of the upper limit (or lower limit) of the effective temperature range of the corresponding tolerance level in Table 1 shall be checked;
3, Pt100 and second-class standard platinum resistance thermometer resistance measurement, should use four-wire measurement method;
4. When the Pt100 is verified, the thermal resistance current should be no more than 1 mA. It is better to use a digital multimeter that meets the measurement accuracy requirements. The platinum resistance method is alternately repeated no less than 4 times (including current commutation), and the average value is taken as the measurement result.
Verification of R0 (resistance at 0 °C)
1. In the freezing point tank (or a thermostatic bath with 0 ° C, the deviation does not exceed ± 0.2 ° C). Measure the resistance value of Pt100 and the temperature measured by the second-class standard platinum resistance thermometer, and compare and calculate the deviation value of 0 °C ± Δt0;
2. The thermal resistance of the protective tube can be removed. It should be placed in a glass test tube with an inner diameter slightly larger than the diameter of the temperature sensing element. After the nozzle is tightly packed with absorbent cotton or cork, insert it into the ice point groove where the ice water is well mixed, and the insertion depth should be no less than 30mm;
3. The non-removable Pt100 thermal resistance of the protection tube can be directly inserted into the medium, and the measurement data can be read when the measurement data is stable;
4. If a 0°C thermostat is used, the Pt100 thermal resistance should have sufficient insertion depth to minimize heat loss;
5. To verify Pt100 thermal resistance above AA level, in order to reduce test uncertainty, it is appropriate to measure it in water three-phase point bottle.
Industrial Pt100 Thermal Resistance Allowance Error Table
Verification of R100 (resistance at 100 °C) and Rt (resistance at t°C)
1. Measure the resistance value of Pt100 thermal resistance R100 in a constant temperature bath at 100 ° C, and compare it with the temperature measured by a second-class standard platinum resistance thermometer, and calculate its deviation value Δt100 of 100 ° C;
2, the Rt test of the detachable Pt100 thermal resistance is the same as the R0 test, the temperature sensing element is placed in the glass test tube (the test temperature should be placed in the quartz test tube above 400 °C);
3. Insert the thermostatic bath and ensure sufficient insertion depth. After the heat balance, continue to increase the insertion depth by l0mm. The change in resistance value after re-achieving the heat balance shall not exceed 5% of the allowable error;
4. When the temperature t is higher than 500 ° C, the thermal resistance should be cooled to 0 ° C with the rate of less than 1 ° C / min, and then taken out from the temperature control tank;
5. The temperature of the test point of the constant temperature bath should not exceed ± 2 ° C, and the change within 10 min should not exceed ± 0.02 ° C.