How to choose the thermocouple index number and corresponding model?

Two conductors with different compositions (called thermocouple wires or thermoelectric electrodes) are connected at both ends to form a circuit. When the temperature of the junction is different, an electromotive force is generated in the circuit, which is called thermoelectric effect, and this electromotive force is called thermoelectric potential. Thermocouples use this principle for temperature measurement, where the end directly used to measure the temperature of the medium is called the working end (also known as the measuring end), and the other end is called the cold end (also known as the compensating end); Connect the cold end to the display instrument or matching instrument, and the display instrument will indicate the thermoelectric potential generated by the thermocouple.

Commonly used thermocouples can be divided into two categories: standard thermocouples and non-standard thermocouples. The standard thermocouple referred to refers to a thermocouple that has a national standard that specifies the relationship between its thermoelectric potential and temperature, allows for errors, and has a unified standard scale. It has a matching display instrument available for selection. Non standardized thermocouples are not as widely used or of the same order of magnitude as standardized thermocouples, and generally do not have a unified calibration table. They are mainly used for measurements in certain special occasions. Since January 1, 1988, all thermocouples and thermistors in China have been produced in accordance with IEC international standards, and seven standardized thermocouples, namely S, B, E, K, R, J, and T, have been designated as unified design thermocouples in China.

There are mainly several types including S, R, B, N, K, E, J, T, etc. Among them, S, R, and B belong to precious metal thermocouples, while N, K, E, J, and T belong to low-cost metal thermocouples. The following is an explanation of the thermocouple graduation number: S Platinum Rhodium 10 Pure Platinum R Platinum Rhodium 13 Pure Platinum B Platinum Rhodium 30 Platinum Rhodium 6K Nickel Chromium Nickel Silicon T Pure Copper Copper Nickel J Iron Copper Nickel N Nickel Chromium Silicon Nickel Silicon E Nickel Chromium Copper Nickel.