A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming electrical junctions at differing temperatures. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature.

Type K Thermocouple is the most common general-purpose thermocouple with a sensitivity of approximately 41 µV/°C with it's temperature range of -200°C to 1300°C and accuracy +/- 0.75%

Type J Thermocouple has a more restricted range −40°C to 750°C than type K but higher sensitivity of about 50 µV/°C with accuracy +/- 0.75%.