Knowledge sharing on the specific application and usage principles of thermocouples

When it comes to thermocouples, there are still many people who do not know exactly what they are. Although they are used in many industries, as equipment with high technical tests, most people are not sure how they are used as a foundation. Now let's have a deeper understanding and analysis of thermocouples.
As a temperature measurement sensor, thermocouples are usually used in conjunction with temperature transmitters, regulators, and display instruments to form a process control system, which is used to directly measure or control the temperature of fluids, steam, gas media, and solid surfaces within the range of 0-1800 ℃ in various production processes.
A thermocouple is a circuit composed of two conductors with different compositions connected at both ends. When the temperature of the two junction points is different, thermal current will be generated in the circuit. If there is a temperature difference between the working end and the reference end of the thermocouple, the display instrument will indicate the temperature value corresponding to the thermoelectric potential generated by the thermocouple. The thermoelectric heating of platinum rhodium thermocouples will increase with the temperature of the measuring end, and its size is only related to the thermocouple material and the temperature at both ends, and is independent of the length and diameter of the thermoelectric electrode.
The appearance of various platinum rhodium thermocouples is often very different due to needs, but their basic structure is generally the same, usually composed of main components such as thermal electrodes, insulation sleeve protective tubes, and junction boxes.
Installation and Use
The installation location of thermocouples should be convenient for construction and maintenance. It should be avoided to be near the furnace door, or near the heating element or in strong magnetic fields, and the temperature at the junction box should not exceed 100 ℃. Installation position note: t represents the measured temperature value (℃) of the temperature sensing element, which should be kept as vertical as possible, but must be installed diagonally when there is a flow rate. The outlet of the junction box should face downwards.
Thermocouples with ceramic protective tubes must avoid sudden cooling and heating to prevent bursting. During installation, a place that does not hinder the movement of the heated object should be selected. Ceramic protective tubes cannot measure liquid temperature.
Thermocouples should be wired according to regulations, with leads avoiding heat sources. When wiring, the polarity of the compensating wire should not be reversed. Regularly check the condition of the protective tube, take immediate measures if oxidation or deformation is found, and calibrate regularly.
If you didn't know how to install thermocouples before, I believe you can clearly understand how to install them through the above content.
At present, household gas stoves equipped with thermocouple flameout protection devices can effectively prevent accidental flameout and prevent accidents caused by gas leakage. This device has the advantages of simple structure, convenient maintenance, durable components, and good reliability, and has been widely used in domestic gas stoves of various brands in China and * *.

The detection principle of thermocouples
If the two ends of two different conductors are welded together to form a circuit, different temperatures are applied to each end of the welding. The end with high temperature is called the hot end or working end; The end with low temperature is called the cold end or free end. In this way, an electromotive force will be generated in the circuit, which is called the thermoelectric effect* Finally, the combination of two different conductors forms a thermocouple. Different alloys generate different thermoelectric potentials. Thermocouples are usually used as temperature sensor components and instruments to measure, indicate, or control temperature.