Standard commonly used for armoured thermocouples

Commonly used armored thermocouple can be divided into two categories: standard thermocouple and non-standard thermocouple. The call standard thermocouple refers to the national specification rules of the thermoelectric potential and temperature relationship, error allowed, and has a consistent standard thermometer thermocouple, it has its supporting appearance available for selection. Non-standard thermocouple in the application range or order of magnitude are not as good as standardized thermocouple, generally there is no consistent indexing table, mainly used for some special occasions of measurement.

China from January 1, 1988, armored thermocouple and thermal resistance in accordance with IEC international specifications production, and designated S, B, E, K, R, J, T seven standardized thermocouple for China's consistent design type thermocouple.

In order to ensure that the thermocouple can work reliably and stably, its structural requirements are as follows:

(1) It is necessary to weld the two thermal electrodes of the thermocouple firmly;

(2) The two thermal electrodes should be well insulated from each other to prevent short circuit;

(3) The connection between the compensation wire and the free end of the thermocouple should be convenient and reliable;

④ The protective sleeve should be able to ensure sufficient isolation between the thermal electrode and the harmful medium.

Temperature compensation of cold end of armored thermocouple

Because armoured thermocouple materials generally are more valuable (especially when choosing precious metals), temperature measuring points to the appearance of the distance is far away, in order to save thermocouple materials, reduce cost, generally choose the compensating conductor (free) of the cold junction of the thermocouple extends to the relatively stable control indoor temperature and cohesion to the appearance on the terminal. It is necessary to point out that the function of the thermocouple compensation wire only extends the hot electrode, so that the cold end of the thermocouple moves to the outer terminal of the control room. It can not eliminate the influence of the temperature change of the cold end on the temperature measurement, and can not compensate. Therefore, other correction methods should be used to compensate for the influence of temperature measurement on the cold end temperature t0≠0℃.

In the use of thermocouple compensation wire it is necessary to pay attention to the model matching, polarity can not be connected wrong, compensation wire and thermocouple connection temperature can not exceed 100℃