Thermocouple

A thermocouple is a temperature sensor made from two different metals joined at one end. The junction produces a small voltage that changes with temperature, which a meter converts into a reading. Thermocouples are cheap, rugged and can measure temperatures from below freezing to over 1000 degrees Celsius.

Example: Many digital multimeters come with a thin wire probe with a bead at the tip, which is a thermocouple for measuring the temperature of a soldering iron or hot plate.