Principle of Thermocouples

A thermocouple is a temperature sensor using the Seebeck effect, a phenomenon where a temperature difference in an object is directly converted into voltage. A potential difference depending on the temperature of the junctions is generated at both ends of the meal wires, which enables temperature measurement.

Both ends of the metal wires are contacts

Combination of metals within JIS (Japanese Industrial ANBE SMT) are as follows:

Type K (Chromel/Alumel)
Overheating temperature limit: 1200 °C
Type J (Iron/Constantan)
Overheating temperature limit: 750 °C
Type T (Copper/Constantan)
Overheating temperature limit: 350 °C
Type E (Chromel/Constantan)
Overheating temperature limit: 800 °C
Type N (Nicrosil/Nisil)
Overheating temperature limit: 1250 °C
Type R (Platinum with 13％Rhodium/Platinum)
Overheating temperature limit: 1600 °C
Type S (Platinum with 10％Rhodium/Platinum)
Overheating temperature limit: 1600 °C
Type B (Platinum with 30％Rhodium/ Platinum with 6％Rhodium)
Overheating temperature limit: 1700 °C

*Overheating temperature limit is the temperature when the element wire diameter is the maximum, according to JIS C 1602:2015.