A basic temperature sensor, like a thermocouple, measures temperature based on the principle of the Seebeck effect. The Seebeck effect states that when two dissimilar metals are joined together at two different points and there is a temperature difference between the two points, a voltage is generated across the junctions.
A thermocouple typically consists of two different metal wires or conductors, known as the "legs" of the thermocouple. These two legs are connected at one end to form the measuring junction, and the other ends are connected to a measurement device, such as a voltmeter.
When the measuring junction is exposed to a temperature different from the reference junction (usually kept at a known or constant temperature), an electric potential difference or voltage is generated due to the Seebeck effect. This voltage is proportional to the temperature difference between the measuring and reference junctions.
The voltage generated by the thermocouple is relatively small, so it needs to be amplified and converted into a temperature reading using suitable electronics. The measurement device (e.g., voltmeter or thermocouple temperature reader) interprets the voltage and correlates it to the corresponding temperature value based on known calibration data for that specific thermocouple type.
It's essential to know the characteristics of the thermocouple's materials and their temperature-to-voltage relationship, which is usually provided in the form of a calibration table or equation. Different types of thermocouples (e.g., Type K, Type J, Type T, etc.) use different combinations of metal alloys, making them suitable for various temperature ranges and applications.
In summary, a basic temperature sensor (thermocouple) measures temperature by generating a voltage through the Seebeck effect when there is a temperature difference between the measuring junction and the reference junction. This voltage is then converted into a temperature reading using appropriate electronics and calibration data specific to the thermocouple type.