What difference between thermocouple and thermocouple _ instrument

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. Thermocouple and thermocouple temperature measurement on all belong to the contact temperature measurement, although the effect is same measuring the temperature of the object, but the principle and characteristics of them is different. Although thermocouple is widely applied in industry, but because of his 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. Thermocouple temperature measurement is widely used in the temperature of the device, its main characteristic is to kiss a wide 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. 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 produced by electric potential is not the same, the contact potential as its name implies is refers to the two different conductor in contact, because of their different electron density so 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. Thermocouple 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. As to distinguish the type of thermocouple and thermocouple compensation wire, but it does not need and is much cheaper than hot accidentally. In industry measurement of low temperature and bimetallic thermometer. 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. The principle of thermocouple thermometer is the use of a conductor or the resistance with the temperature change of the properties of the semiconductor. The main advantage of the thermocouple thermometer has high measuring accuracy, good reproducibility. Has larger measurement range, especially in low temperature; Easy to use in the automatic measurement, also facilitate remote measurement. Similarly, thermocouple is flawed, and in the high temperature ( More than 850 ℃) Measurement accuracy is bad; Easy to oxidation and corrosion resistance. Thermocouple material used at present, there are mainly platinum, copper, nickel, etc. , using these materials mainly is that they are in common temperature period of the temperature and the ratio of the resistance is the linear relationship.