Commonly used in low temperature zone thermocouple is a kind of temperature detector, widely used in industrial temperature measurement, and has high measurement precision, the advantages of stable performance. And industrial measurement, thermocouple type is much also, besides using metal thermoelectric materials, as well as copper, nickel, iron, iron - Nickel, etc. The four types of thermocouple normal thermocouple: 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. Thermocouple, thermocouple is by thermal components ( The resistor body) , wire, insulation materials, stainless steel casing combination solid body, its diameter is commonly phi - 2 - Phi is 8 mm, achieve more xiaoke phi is 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 and resistance to vibration and impact resistant; 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. Flame-proof thermocouple can be used in the bla - B3c level zone with explosion danger place temperature measurement.