What does a thermocouple measure?

A thermocouple is a temperature-sensing device that operates based on the principle of the thermoelectric effect. When two different metals are joined at one end to form a junction and there is a temperature difference between that junction and the other ends of the metals, a voltage is generated that is proportional to the temperature difference. This voltage can be measured and converted into a temperature reading, making thermocouples widely used in various applications for measuring temperature in many industrial and laboratory settings.

This property of thermocouples is what makes the answer about temperature accurate, as they are specifically designed to provide reliable temperature measurements over a wide range of conditions.