(1) the types of thermocouple

Commonly used thermocouple could be divided into two types: standard thermocouple and non-standard thermocouple. Standard thermocouple is refers to the national standard specifies its thermoelectric potential and the relationship between temperature, permissible error, and a unified standard score table of thermocouple, it has with matching display instrument to choose from. Non-standard thermocouple or on the order of magnitude less than the range using standardized thermocouple, generally no unified indexing table, mainly used for the measurement of some special occasions.

(2) the thermocouple materials

In theory, any two conductors can be made into thermocouple, but in fact is not all materials can make thermocouple, reason of hot electrode materials must meet the following:

Thermocouple materials subjected to temperature after can produce high thermoelectric potential and thermoelectric potential and temperature of the relationship between the best linear or approximate linear single valued function relation;

Can measure the high temperature and in a wider temperature fan domestic application, after long-term use of physical, chemical properties and pyroelectric properties remained stable;

Requirements for the temperature coefficient of resistance material is small, high resistivity, good conductivity, heat capacity is small;

Better repeatability, easy to mass production and exchange, to formulate unified indexing table; Good mechanical performance, material evenly; Rich in resources, the price is cheap.

(3) to ensure that the thermocouple is reliable, steady work, the structure of thermocouple requirements are as follows:

(1) of the two thermocouple thermal electrode welding must be strong;

(2) two hot electrode should be well insulated between each other, in case of short circuit;

(3) compensation conductor should be connected to the free cod of a thermocouple to be convenient and reliable;

(4) protect casing thermal electrodes should be able to make sufficient isolation and harmful medium.