Types of thermocouples and detailed classification of materials

Commonly used thermocouples can be divided into two categories: standard thermocouples and non-standard thermocouples. The standard thermocouple refers to the thermocouple whose thermoelectric potential and temperature relationship, allowable error, and unified standard scale are specified by the national standard. It has a matching display instrument for selection. Non-standard thermocouples are not as good as standardized thermocouples in terms of use range or order of magnitude, and generally do not have a unified scale. They are mainly used for measurements in certain special occasions. Standardized thermocouples Since January 1, 1988, China has produced all thermocouples and thermal resistors according to IEC international standards, and designated seven standardized thermocouples, S, B, E, K, R, J, and T, as China's unified design thermocouples.

Commonly used thermocouple materials

Thermocouple graduation number Thermocouple material Use temperature range (℃)

Thermocouple

Positive electrode Negative electrode

S Platinum-rhodium alloy (rhodium content 10%) Pure platinum 0-1400

R Platinum-rhodium alloy (rhodium content 13%) Pure platinum 0-1400

B Platinum-rhodium alloy (rhodium content 30%) Platinum-rhodium alloy (rhodium content 6%) 0-1400

K Nickel-chromium-nickel-silicon -200-+1000

T Pure copper Copper-nickel -200-+300

J Iron Copper-nickel -200-+600

N Nickel-chromium-silicon-nickel-silicon -200-+1200

E Nickel-chromium Copper-nickel -200-+700