Thermocouple is a kind of common temperature measuring instrument, has a certain application in many fields. A variety of thermocouple, including commonly used has the following kinds: common thermocouple, thermocouple, end thermocouple, flame-proof thermocouple. Normal thermocouple: industrial 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, thermocouple is by thermal components ( The resistor body) , wire, insulation materials, stainless steel casing combination solid body, its diameter is generally from 2 to 8 mm, xiaoke reaches 0. 25mm。 Compared with ordinary thermocouple, it has the following advantages: (1) small volume, no internal air gap and thermal inertia, the measured value after small; (2) good mechanical properties, resistance to vibration and shock. (3) can bend, easy to install (4) long service life. End thermocouple: end thermocouple temperature sensing element resistance wire winding by special processing, close to the face in the thermometer. Compared with general axial thermocouple, it can reflect more correctly and quickly end face of the actual temperature being measured, is suitable for measuring temperature bearing and other parts of the face. Flame-proof thermocouple, flame-proof thermocouple through the special structure of the junction box, its shell internal explosive mixed gas by affected by sparks or electric arc explosion limit within the junction box, that wouldn't make production field explosion. Flameproof thermocouple can be used in the Bla ~ B3c zone with explosion danger place temperature measurement.