Although thermocouple is widely applied in industry, but because of its temperature range makes his application by certain restrictions, thermocouple temperature measurement principle is based on the conductor or the resistance of the semiconductor characteristics of the changes with temperature changes. Its many advantages, can also remote transmission signal, high sensitivity, strong stability, compatibility and accuracy are better, but you need to power, can't instantaneous measured the change in temperature. Industrial thermocouple usually use Pt100, Pt10, Cu50, Cu100, platinum thermocouple temperature measurement range is generally 200 - below zero 800 ℃, copper thermocouple is 40 to 140 ℃ below zero. As to distinguish the type of thermocouple and thermocouple compensation wire, but it does not need and is cheaper than thermocouple. Industrial thermocouple as the temperature measurement sensor, usually with temperature transmitter, controller and display instrument, process control system, to directly measure or control - all kinds of production process 200℃- 500 ℃ range of liquid, steam and gas medium, as well as the temperature of the solid surface. Thermocouple is the use of the material when the temperature changes itself along with the change of resistance and characteristics to measure temperature, when the temperature of the measured medium body with the tonsure to exist, the temperature of the measured average scope of thermal components in the medium, although the appearance of all kinds of thermocouple temperature difference is very big, but they are roughly similar, the basic structure of the general temperature inductive element, insulation casing, protection tube, and junction box and other major parts. 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 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, achieve more xiaoke phi is 0. 25mm。 Compared with conventional type thermocouple, it has the following advantages: (1) small volume, no internal air gap, 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. Thermocouple temperature measuring instrument is commonly used in temperature measuring element, is made up of two different components of the conductor when two ends synthesis loop, when the two junction thermocouple temperature is not at the same time, will produce thermal current in the circuit. If the work end of the thermocouple with the reference entity temperature difference, display instrument will indicate the thermocouple thermoelectric potential of the corresponding temperature value. Thermocouple is a kind of temperature sensor, it is smaller than the diameter of a prefabricated thermocouple, flexible, good vibration resistance, suitable for installation in the case of prefabricated thermocouple can't install, the company produces the thermocouple used to introduce thermocouple temperature measuring element, therefore, is accurate, sensitive, fast thermal response time, stable quality, long service life, etc.