Commonly used thermocouples can be divided into two categories: standard thermocouples and non-standard thermocouples. The called specification thermocouple refers to the thermocouple that the national standard stipulates the connection between the thermoelectric potential and the temperature, the error is promised, and the consistent index table is provided. It has the display appearance matching with it. Non-standardized thermocouples are inferior to standardized thermocouples in terms of application range or magnitude. Generally, there is no consistent indexing table, which is mainly used for measurement in some special occasions.

Seven standardized thermocouples of S, B, E, K, R, J and T are consistently designed thermocouples in China.

There are several types of thermocouples, such as S, R, B, N, K, E, J, and T. In the meantime, S, R and B belong to the noble metal thermocouple, and N, K, E, J and T belong to the inexpensive metal thermocouple.

The following is an explanation of the thermocouple index number.

Platinum rhodium 10-platinum thermocouples (S-type thermocouples) are noble metal thermocouples. The diameter of the wire is specified to be 0.5mm, the tolerance is -0.015mm, and the nominal chemical composition of the positive electrode (SP) is platinum-rhodium alloy, which contains 10% yttrium, 90% platinum, and the negative electrode (SN) is pure platinum. Commonly known as a single platinum rhodium thermocouple. The thermocouple has a maximum operating temperature of 1300 ° C for a long time and a maximum operating temperature of 1600 ° C for a short period of time.