(1) ordinary thermocouple: the ordinary type of thermocouple installed by the connection type can be divided into fixed screw connection, fixed flange connection, the activities of the flange connection, no fixed device, and other forms. Although their structure and shape are not the same, but their basic components are roughly the same. It is usually the main part of the heat and power pole, the insulation material protection tube and the junction box.
The diameter of the electrode is determined by the price of the material, the mechanical strength, the electrical conductivity and the temperature measurement range of the thermocouple. The thermal power of precious metals is much more than the diameter of 0.3-0.65mm Oh filament, the average diameter of the metal is generally 0.5-3.2mm.
An insulating sleeve is used to ensure that the electrical insulation between the two electrode and the electrode and the protective tube is normally used with a high temperature resistant ceramic tube with a hole.
The protective sleeve is outside of the thermal insulation and the insulating casing, and the function is to protect the thermoelectric electrode (insulating material) from chemical corrosion and mechanical damage. At the same time to facilitate the installation and maintenance of instrumentation. Protective sleeve material should have high temperature resistance, corrosion resistance, good air tightness, high mechanical strength, thermal conductivity and high performance, there are metal, nonmetal and metal ceramic three categories, including stainless steel is one of the most commonly used, can be used for temperature in 900 DEG C occasions. Can choose different materials according to the different use of the environment of the protective tube.
The connection box is used for connecting the thermocouple end and the lead out wire, and the lead wire is generally matched with the thermocouple. The junction box is sealed and protected from corrosion.
(2) armoured thermocouple, armoured thermocouple is formed by stretch processing is a thermocouple wire, insulation material and a metal casing three solid combination. It can be done very thin, very long, can be used in the measurement of arbitrary bending. The casing material is copper, stainless steel or nickel base high temperature alloy and so on. The thermal insulation material is filled between the electrode and the casing, and the insulation material is commonly used in the insulation material such as Magnesium Oxide, alumina, etc.. The main features of the sheathed thermocouple measuring end of the heat capacity of small, fast dynamic response; high mechanical strength; immunity, and can be installed in the complex structure of the device. It has been widely used in many industrial sectors.
