Thermocouple types commonly used thermocouple can be divided into: standard thermocouple and non-standard thermocouple two kinds big. Standard thermocouple refers to the national standard specifies its thermoelectric potential and the relationship between temperature, permissible error, and a unified standard score table of thermocouple, it has with matching display instrument to choose from. Non-standard thermocouple or on the order of magnitude less than the range using standardized thermocouple, generally no unified indexing table, mainly used for the measurement of some special occasions. Standardized thermocouple since January 1, 1988 in our country, the thermocouple and thermocouple were manufactured according to IEC international standard, and specify the S, B, E, K, R, J, T seven standardization thermocouple type thermocouple for our country unified design. The structure of thermocouple in order to keep the thermocouple is reliable, steady work, the structure of its request below 1, the composition of the thermocouple two hot welding electrode must be firmly 2, two hot electrode should be well insulated between each other, in case of short circuit 3, compensation conductor should be connected to the free cod of a thermocouple to 4, convenient and reliable protection casing should ensure hot electrode and harmful medium fully isolated thermocouple cold end temperature compensation due to the thermocouple materials are generally more expensive ( Especially when using precious metals) And temperature measuring points are far away the distance to the instrument, in order to save thermocouple materials, reduce cost, usually adopt the compensating conductor (of the cold junction of the thermocouple The free end) Reaches to the relatively stable control indoor temperature and connected to the meter terminals. It must be pointed out that the role of the thermocouple compensation wire only extend thermal electrode, make moves to the control room of the cold junction of the thermocouple meter terminal, it itself does not eliminate the cold end temperature change on the influence of temperature, no compensation. So, still need to take some of the other correction method to compensate of the cold end temperature t0 indicates influence on measuring temperature 0 ℃. Generally display and control instrument has automatic temperature compensation system, do not need to worry about. Instrument must pay attention to in using thermocouple compensating conductor model match, the polarity can't fault, the compensation to the wire connected to the thermocouple temperature generally does not exceed 100 ℃.