A thermocouple is a sensor for measuring temperature. It converts heat energy into an electric signal that can be analyzed by a thermocouple thermometer to determine the temperature. A thermocouple consists of two dissimilar metals that are joined together at one end, which produce a small voltage between their other ends for a given temperature.
Thermocouples come in many different combinations of metals and calibrations.
The most common types are J, K, T, and E. Each of these types of calibrations has a specific temperature range and environment in which it can operate. They can be used in vacuum and in oxidizing, reducing, or inert atmospheres. They resist corrosion in moist atmospheres and are appropriate for subzero temperatures. The simplest thermocouple probe consists of two wires twisted or soldered together at one end with the other end connected to the terminals of a voltmeter. These probes can be purchased from companies or made in the lab.