There are many varieties and types of thermocouples, which are commonly used in laboratory high temperature heating equipment such as high temperature box furnace, vacuum tube furnace, muffle furnace and box atmosphere furnace developed and produced by us. Here we, Zhengzhou Kejia Electric Furnace Co., Ltd., share the structure and type of thermocouple for you.
Composition of thermocouple
In actual temperature measurement, thermocouples with only two thermoelectric electrodes are rare. Ordinary thermocouple is usually composed of four parts: thermal electrode, insulating tube, protective sleeve and junction box.
(1) Thermoelectric electrode: Thermoelectric electrode is the core part of thermocouple. The thermoelectric electrode of ordinary thermocouple is usually processed into wire shape and welded at one end. The diameter of the thermoelectric electrode is mainly determined by the material price, mechanical strength, the use of the thermocouple and the temperature measurement range. The diameter of precious metal thermoelectric electrode is generally 0.3-0.65mm, and the diameter of low metal thermoelectric electrode is generally 0.5-3.2mm.
The length of the thermoelectric electrode is usually made into various specifications within the range of 100-200mm for practical use.
(2) Insulating tube: the insulating tube, also known as insulator, is equipped with a through-hole sleeve on the thermoelectric electrode to separate two electrodes and the isolating electrode from the metal protective sleeve, otherwise the measurement error will be caused by the thermal potential loss due to short circuit. Insulators are usually made of high temperature resistant insulating materials, such as ceramics, quartz, aluminum oxide, magnesium oxide, etc., with circular or elliptical section and single hole, double hole, four hole, etc.
(3) Protective tube: the thermoelectric electrode sheathed with insulating tube is installed in a closed protective tube at one end. The function of the protective tube is to prevent or reduce the direct erosion of various harmful gases and substances on the thermoelectric electrode and the direct rush of high-temperature flame or air flow; Prevent direct contact between conductive medium and thermoelectric electrode; In addition, it has the function of fixing and supporting the thermoelectric electrode. Therefore, the protection tube of the thermocouple plays a major role in prolonging the service life of the thermoelectric electrode and ensuring the measurement accuracy.