Judgment Of The Graduation Number And Polarity Of The Compensation Wire

The reliable and commonly used method is the test method, which is to strip the insulation layer at both ends of the compensation wire, twist the two wires together to make the hot end of the thermocouple, and put it in boiling water. The other end of the two wires is connected to the direct current Connect the position difference meter (should not be connected to the moving coil direct-reading mV meter, because the reading of the current is low when measuring), compare the measured thermoelectric potential with Table 1, and the closest one is the compensation wire Degree number, the polarity of the compensation wire can be determined according to the positive and negative poles of the potentiometer. Since the reference junction temperature of the thermocouple formed by the compensation wire during the test is not necessarily 0°C, such as 20°C, the measured thermoelectric potential is lower than the thermoelectric potential value at the reference junction of 0°C. Take a certain compensation wire with an unknown division number as an example. If the reference junction temperature is about 20°C and the measured value is within the range of 3.928±0.150mV, it can be judged that the division number of this compensation wire is K. 3.928 is the difference of thermoelectric potential between 100℃ and 20℃ of K index thermocouple, and 0.150 is the tolerance of K index ordinary compensation wire.