Types And Structure Formation Of Thermocouples
(1) Types of thermocouples
Commonly used thermocouples can be divided into two categories: standard thermocouples and non-standard thermocouples. The called standard thermocouple refers to the thermocouple whose thermoelectric power and temperature are stipulated in the national standard, the allowable error, and there is a unified standard graduation table. It has a matching display instrument for selection. Non-standard thermocouples are inferior to standardized thermocouples in the scope or order of magnitude, and there is generally no unified indexing table, which is mainly used for measurement in some special occasions.
Standardized thermocouples. Since January 1, 1988, all thermocouples and thermal resistances have been produced in accordance with IEC international standards, and seven standardized thermocouples, S, B, E, K, R, J, and T, are designated as my country’s unified design. Thermocouple.
(2) The structure of the thermocouple In order to ensure the reliable and stable operation of the thermocouple, its structure requirements are as follows:
①The welding of the two thermoelectrodes forming the thermocouple must be firm;
②The two hot electrodes should be well insulated from each other to prevent short circuit;
③The connection between the compensation wire and the free end of the thermocouple should be convenient and reliable;
④The protective sleeve should be able to ensure that the hot electrode is fully isolated from the harmful medium.
