An instrument which utilizes an electrical precess to measure temperature; such as, a thermocouple or resistance thermometer.

A thermocouple is a thermoelectric device used to measure temperatures accurately, especially one consisting of two dissimilar metals joined so that a potential difference generated between the points of contact is a measure of the temperature difference between the points.

One junction is at the temperature to be measured, the second is at a fixed temperature. The electromotive force generated depends upon the temperature difference.