Thermocouple is a temperature sensing element that measures temperature by measuring the electromotive force generated when two conductors of different compositions are welded together and the two ends are at different temperatures. It is a transducer that converts temperature signals into electrical signals, which are then displayed by an indicating instrument.
The basic principle of temperature measurement by thermocouple is thethermoelectric effect. Two metal conductors of different compositions are connected end to end to form aclosed loop. If the temperatures at the two junctions are different, athermoelectromotive force is generated in the loop, forming athermoelectric current. This is the thermoelectric effect. A thermocouple is made by welding two different metal materials at one end. The welded end is called the measuring end, and the unwelded end is called the reference end. The reference end is usually kept at a constant temperature (e.g., 0°C) during use. When the measuring end is heated, a thermoelectromotive force is generated at the junction. If the reference end temperature is constant, the magnitude and direction of the thermoelectromotive force depend only on the characteristics of the two metal materials and the temperature of the measuring end, and are independent of the fineness and length of the thermocouple. When the temperature of the measuring end changes, theelectromotive force also changes accordingly, and there is a fixed functional relationship between temperature and thermoelectromotive force. Using this relationship, temperature can be measured.
A sheathed thermocouple electrode consists of two conductors of different compositions welded at both ends to form a loop. The direct temperature measurement end is called the working end, and the terminal end is called thecold end, also known as the reference end. When there is a temperature difference between the working end and the reference end, athermoelectric current is generated in the loop. When connected to a display instrument, the instrument will indicate the temperature value corresponding to thethermoelectromotive force generated by the thermocouple. The thermoelectromotive force of a sheathed thermocouple increases as the temperature of the measuring end rises. The magnitude of the thermoelectromotive force depends only on the material of the thermocouple conductors and the temperature difference between the two ends, and is independent of the length and diameter of the thermoelectrodes. The structural principle of a sheathed thermocouple is that it is made by integrally drawing conductors, high-insulation magnesium oxide, and an outer stainless steel protective tube together multiple times. The sheathed thermocouple product mainly consists of ajunction box, terminals, and a sheathed thermocouple as the basic structure, equipped with various installation and fixing devices. [2]
Basic Structure
The sheathed thermocouple mainly consists of ajunction box, terminals, and a sheathed thermocouple element as the basic structure, equipped with various installation and fixing devices. The installation and fixing devices are provided for user installation. Sheathedthermocouples include: without fixing device, fixed ferrule type, movable ferrule type, fixed flange type, movable flange type, etc.
