Temperature sensors are one of the earliest developed and applied types of sensors. The temperature sensor greatly exceeds other sensors. Since the early 17th century, people have been using temperature for measurement. With the support of semiconductor technology, semiconductor thermocouple sensors, PN junction temperature sensors, and integrated temperature sensors have been developed successively in this century.

When two conductors of different materials are connected to each other at a certain point, heating the connection point will result in a potential difference in the areas where they are not heated. The value of this potential difference is related to the temperature of the measurement point in the unheated area and the materials of these two conductors. This phenomenon can occur over a wide temperature range. If the potential difference is accurately measured and the ambient temperature of the unheated area is also measured, the temperature of the heating point can be accurately determined. Due to the need for two different materials of conductors, it is called a "thermocouple". Thermocouples made of different materials are used in different temperature ranges, and their sensitivity also varies.

Thermocouple sensors have their own advantages and disadvantages. They have low sensitivity, are easily affected by environmental interference signals, and are also susceptible to temperature drift from preamplifiers. Therefore, they are not suitable for measuring small temperature changes. Due to the sensitivity of thermocouple temperature sensors being independent of the thickness of the material