What is a thermocouple and what is it used for?

• A. A temperature sensor that generates a voltage proportional to temperature difference.
• B. A device that measures humidity in the air.
• C. A sensor that converts mechanical motion into electrical energy.
• D. A device that stores electrical energy.

Answer: (A)

Thermocouples rely on the Seebeck effect: two dissimilar metals joined at one end produce a small voltage that depends on temperature. The hot junction senses temperature and the voltage is measured against a reference junction. That output voltage is proportional to the temperature difference, so with calibration you convert the voltage into a temperature reading. This makes thermocouples simple, fast, and rugged temperature sensors that can handle a wide range of temperatures in many industrial applications. They aren’t humidity sensors, they don’t generate power from motion, and they don’t store energy.