Selection and verification method of pt100 thermocouple temperature sensor

Selection of Pt100 calibration points and basic methods:

1. The calibration points of each level of Pt100 should be 0℃ and 100℃, and the compliance of the actual resistance temperature coefficient a should be checked;

2. When △a does not meet the requirements, the upper (or lower) limit of the effective temperature range of the corresponding tolerance level in Table 1 should be calibrated;

3. The resistance value measurement of Pt100 and second-class standard platinum resistance thermometer should adopt the four-wire measurement method;

4. When calibrating Pt100, the current passing through the thermal resistor should not be greater than 1mA, and a digital multimeter that meets the measurement accuracy requirements should be selected; the platinum resistance method should be repeated alternately for no less than 4 times (including current reversal), and the average value should be taken as the measurement result.

Verification of R0 (resistance value at 0℃):

1. In an ice point bath (or a constant temperature bath with 0℃, with a deviation of no more than ±0.2℃), measure the resistance value of Pt100 and the temperature measured by a second-class standard platinum resistance thermometer, and compare and calculate the deviation value ±△t0 of 0℃;

2. The thermal resistor with a removable protective tube should be placed in a glass test tube with an inner diameter slightly larger than the diameter of the temperature sensing element. After the tube mouth is plugged with absorbent cotton or a wooden plug, it should be inserted into the ice point bath with ice water fully mixed. The insertion depth should not be less than 30mm;

3. The Pt100 thermal resistor with an unremovable protective tube can be directly inserted into the medium. The measurement data can be read only when it is stable during verification;

4. If a 0℃ constant temperature bath is used, the Pt100 thermal resistor should have a sufficient insertion depth to minimize heat loss;

5. When verifying Pt100 thermal resistors above AA level, in order to reduce the test uncertainty, it is advisable to measure in a water triple point bottle.

Verification of R100 (resistance value at 100℃) and Rt (resistance value at t℃):

1. Measure the resistance value of Pt100 thermal resistor R100 in a 100℃ constant temperature bath, and compare it with the temperature measured by a second-class standard platinum resistance thermometer, and calculate its 100℃ deviation value △t100;

2. The Rt verification of the detachable Pt100 thermal resistor is the same as the R0 verification. Place the temperature sensing element in a glass test tube (if the verification temperature is higher than 400℃, place Placed in a quartz test tube);

3. Insert into the thermostat and ensure sufficient insertion depth. After thermal equilibrium, continue to increase the insertion depth by 10mm. After re-reaching thermal equilibrium, the change in resistance value should not exceed 5% of the allowable error;

4. When the temperature t is higher than 500℃, the thermal resistor should be cooled to 0℃ with the tank at a rate of less than 1℃/min, and then taken out of the temperature control tank;

5. The calibration point temperature of the thermostat should not exceed ±2℃, and the change within 10min should not exceed ±0.02℃.

Table of allowable errors of industrial Pt100 thermal resistors

Qualified judgment of R0 and R100 resistance values:

1. Within the effective temperature range, the maximum deviation between the temperature t calculated by the graduation table and the actual temperature of the thermal resistor should not exceed the allowable error value given in the above table.

2. The nominal values ​​of Pt100 (platinum resistor with a resistance of 100 at 0°C) and Cu100 (copper resistor with a resistance of 100 at 0°C) and the ranges of R0 and R100 that meet the tolerance requirements are shown in the table below.