Why is a thermocouple a good device for indicating the temperature

in a car engine?

A thermocouple is a sensor used to measure temperature. Thermocouples are made with two wires of different metals, joined together at one end to form a junction ... Naturally, a thermocouple outputs a millivolt signal, therefore, as the resistance changes, the change in voltage can be measured.

-nat geo

A thermocouple is useful for measuring temperatures in areas that are difficult to reach.