Selection and precautions of thermocouple compensation wire

The choice of compensation wire has a great influence on the accuracy of thermocouple temperature measurement. Instrument operators must be familiar with the performance and indicators of various compensation wires. The following is a brief introduction to the matters needing attention in the use of compensation wire.

1. For S type thermocouple and R type thermocouple, there are SC and RC compensation wires, both of which belong to compensation type compensation wires and have low accuracy in all kinds of compensation wires. The error is small in the range of 0-60℃, but large in the range of 100-150℃. If the measurement accuracy is high, the temperature of the compensation contact must be kept below 100℃.

2, K type thermocouple compensation wire KC type and KX type. KX is an extended compensation conductor, whose characteristic curve is linear over a wide temperature range, with small error, high cost and high resistance. Therefore, in the use of temperature is not high, temperature accuracy requirements are not too strict, should be used in the low-cost compensation wire KC type. Problems needing attention when using compensation wire:

1, all kinds of compensation wire can only be paired with the corresponding model of thermocouple, different models can not be used.

2. Compensation wire has positive and negative poles. When using, the positive and negative poles of the compensation wire shall not be connected incorrectly, otherwise, it will not only fail to compensate, but also cause great measurement error. It has been proved that the error caused by wrong polarity connection of compensating wire is about twice as much as that caused by no compensating wire.

3. The temperature of the connection point of thermocouple and compensation wire shall not exceed the specified operating temperature. Due to exceeding the specified service temperature, the thermoelectric characteristics of the compensation wire and the thermocouple differ greatly, resulting in measurement errors.

4. Since the thermoelectric characteristics of the compensation wire and the thermocouple are not exactly the same, the temperature of the two contacts at the connection is required to be the same, otherwise the measurement error will be caused.

5, according to the different requirements of the display instrument to choose the diameter of the compensation wire. For example, the compensation wire connected with the moving coil instrument can be selected with a thicker diameter to make its resistance value smaller, so that it will not exceed the external resistance value specified by the instrument.

6. In order to facilitate installation, multi-strand compensation wire can be selected, and waterproof, anticorrosive and fireproof compensation wire can also be selected as required.