Thermoelectric potential means the same at both ends of the conductor potential because of the different temperature, different conductors with different electron density, so they produce electric potential is not the same, the contact potential as its name implies is refers to the two different conductor in contact, because the electron density of different produce certain electronic diffusion, when they reach a certain potential, which is formed by the balance after the contact potential depends on the size of the two different conductor material properties and their temperature contact point. There are two kinds of structure of the thermocouple, regular and type. Ordinary thermocouples generally by the hot electrode, insulation tube, to protect casing and junction box parts, and the type of thermocouple is the thermocouple wire, insulation material and metal protective casing combination after assembly, after stretching processing from a combination of a solid. But it takes a special electrical signal of thermocouple wires to pass, this kind of wire we called compensation conductor. Different thermocouples require different compensation conductor, its main function is connected to the thermocouple, away from the power of the reference junction of the thermocouple, so that the reference temperature stability. Compensation conductor is divided into the compensation and extension of two kinds of extension of the chemical composition of the wire and the compensation of thermocouple is the same, but in practice, to extend the type of wire is not used is the same as the thermocouple material of metal, usually use and thermocouple wires to replace with the same electron density. Compensation and thermocouple wires of the wire are generally not very clear, the positive connection of the thermocouple compensating lead red line, while the cathode connecting the rest of the color. Most of the material compensating lead wires are commonly used copper nickel alloy. Thermocouple temperature measurement is widely used in the temperature of the device, it is the main characteristic of wide temperature range, stable performance, simple structure at the same time, the dynamic response is good, add conversion transmitter can far eastone 4 - more 20 ma current signal, convenient automatic control and centralized control. Thermocouple temperature measurement principle is based on thermoelectric effect. Connect the two different conductor or semiconductor into closed loops, when the two contacts in temperature is not at the same time, the circuit will produce thermoelectric potential, this kind of phenomenon called the thermoelectric effect, also known as the seebeck effect. There are two kinds of closed loop of thermoelectric potential of electric potential; The thermoelectric potential and contact potential. Although thermocouple is widely applied in industry, but because of its temperature range make its application is limited by a certain, 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, PT1000 platinum thermocouple temperature measurement range is generally 200 - below zero 800 degrees Celsius, copper thermocouple for 40 to 140 degrees Celsius below zero. As to distinguish the type of thermocouple and thermocouple compensation wire, but it does not need and is cheaper than thermocouple.