Thermocouple type and structure form of thermocouple type commonly used thermocouple can be divided into two categories, thermocouple and non standard thermocouples. Using standard thermocouple refers to the standard specifies the 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. ( 1) The structure of thermocouple thermocouple is reliable, steady work, to ensure that the requirements for its structure is as follows: (1) of the two thermocouple electrode welding must be strong (2) the 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 be convenient and reliable (4) protect casing should ensure hot electrode and harmful medium fully isolated thermocouple cold end temperature compensation as a result of 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 ℃. Must pay attention to when using thermocouple compensating conductor model match, cannot be wrong polarity, compensation conductor should be connected to the thermocouple temperature should not exceed 100 ℃. The application principle of thermocouple thermocouple is commonly used in low temperature zone of a temperature detector. Its main characteristic is high accuracy, stable performance. The platinum thermocouple measurement accuracy is high, yes it is not only widely used in industrial temperature measurement, and is made into standard benchmark instrument. Thermocouple temperature measuring thermocouple temperature measurement principle and the material is based on the metal conductor resistance value increases with the increase of the temperature of the properties for temperature measurement. Thermocouples are mostly made of pure metal materials, the application is a lot of platinum and copper, in addition, now has started using survey, nickel, manganese and rhodium thermocouple materials such as manufacturing. The structure of thermocouple thermocouple industry commonly used thermocouple temperature sensing element ( The resistor body) The structure and characteristics. From the thermocouple temperature measurement principle, the measured the change in temperature is directly measured by thermocouple resistance change, therefore, the wires of a thermocouple body such as a variety of wire resistance change will affect temperature measurement. As to eliminate the influence of the lead resistance with the three wire or four wire system. Thermocouple temperature measurement system of thermocouple temperature measurement system in general by thermocouple, connecting wires and display instrument, etc. Must pay attention to the following two points: (1) the thermocouple and the index number of the display instrument must agree (2) in order to eliminate the influence of the connection wire resistance change, must use three wire connection.