Thermocouples are commonly used temperature measuring components in temperature measuring instruments. It directly measures the temperature and converts the temperature signal into a thermoelectromotive force signal. It is converted into the temperature of the measured medium by electrical instruments (secondary instruments). The appearance of various thermocouple probes is often very different due to needs. However, their basic structures are roughly the same, usually composed of main parts such as a thermode, an insulating sleeve protection tube, and a junction box, and are usually used in conjunction with display instruments, recording instruments and electronic regulators.
Introduction to thermocouples
In the industrial production process, temperature is one of the important parameters that need to be measured and controlled. In temperature measurement, the application of thermocouples is extremely wide. It has many advantages such as simple structure, convenient manufacturing, wide measurement range, high precision, low inertia and easy remote transmission of output signals. In addition, since the thermocouple is a passive sensor, no external power supply is needed for measurement, which is very convenient to use. Therefore, it is often used to measure the temperature of gas or liquid in furnaces and pipes and the surface temperature of solids.
Main features of thermocouple
1. Simple assembly and convenient replacement;
2. Compression spring type temperature sensing element, good seismic performance;
3. High measurement accuracy;
4. Large measuring range (-200℃～1300℃, 270℃～2800℃ under special circumstances);
5. Fast thermal response time;
6. High mechanical strength and good pressure resistance;
7. High temperature resistance can reach 2800 degrees;
8. Long service life.
Structural requirements of thermocouples
In order to ensure the reliable and stable operation of the thermocouple, the structural requirements of the thermocouple are as follows:
1. The welding of the two thermoelectrodes forming the thermocouple must be firm;
2. The two hot electrodes should be well insulated from each other to prevent short circuits;
3. The connection between the compensation wire and the free end of the thermocouple should be convenient and reliable;
4. The protective sleeve should be able to ensure that the hot electrode is fully isolated from the harmful medium.