A basic temperature sensor, such as a thermocouple, measures temperature based on the principle of the Seebeck effect. The Seebeck effect is a phenomenon where a temperature difference between two dissimilar metals or semiconductors generates a voltage difference. This voltage difference can be correlated with the temperature being measured.
A thermocouple consists of two different metal wires joined together at one end to form a junction. When this junction is exposed to a temperature difference (i.e., one end is hotter and the other end is colder), it creates an electromotive force (EMF) or voltage across the two wires. The magnitude of this EMF is directly proportional to the temperature difference between the junction and the other end of the wires.
To measure the temperature with a thermocouple, you need to connect the free ends of the two wires to a measuring instrument, such as a temperature meter or a data acquisition system. The measuring instrument compares the voltage generated by the thermocouple with a reference voltage and converts the difference into a temperature reading using a calibration table or a mathematical formula.
It's essential to understand that the accuracy and temperature range of a thermocouple depend on the materials used for its construction. Different types of thermocouples, such as Type K, Type J, Type T, etc., use different combinations of metals to suit various temperature ranges and applications.