The difference between thermocouple and thermal resistance

Thermocouple and thermal resistance are contact temperature measurement of temperature measurement, although the effect is same measurement temperature of the object, but the principle and characteristics of them is different. 。 The temperature of the thermocouple is * widely used in temperature measuring device, his main characteristic is the wide measuring range, stable performance, at the same time, simple structure, good dynamic response, more can far eastone - 4 20 ma electrical signals to facilitate 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. Thermoelectric potential generated in closed loop is composed of two kinds of potential: the temperature difference between electric 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. The thermocouple of international application has a standard specification, the regulations on international thermocouple is divided into eight different degree, respectively B, R, S, K, N, E, J and T, its measuring temperature of minus 270 degrees Celsius * low measurable, * up to 1800 degrees c, B, R, S belong to platinum series thermocouple, because platinum are precious metals, so they are also known as precious metal thermocouple and the remaining few called cheap metal thermocouple.

there are two kinds of structure of the thermocouple, regular and armor type. Ordinary thermocouples generally by the hot electrode, insulation tube, to protect casing and junction box parts, such as type and armoured thermocouple is the thermocouple wire, insulation material and metal protective casing combination after assembly, after stretching processing from a combination of a solid.

thermocouple signals need to pass a special kind of conductor, the conductor 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 wire is divided into compensation type and extended type two kinds, extend 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.

thermal resistance, although is also widely applied in industry, but because of his temperature range makes his application by certain restrictions, thermal resistance temperature measurement principle is based on a conductor or semiconductor resistance changes with the change in temperature. 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 heat resistance generally adopts Pt100, Pt10 Cu50, Cu100, platinum thermal resistance temperature measurement range is generally 200 - below zero 800 degrees Celsius, the thermal resistance of copper of 40 to 140 degrees Celsius below zero. Thermal resistance and thermocouple as the distinction between the type, but he does not need compensation conductor, and is much cheaper than thermocouple.