Temperature is a fundamental physical quantity, closely related to temperature in all natural processes. Temperature sensors are the earliest developed and most widely used type of sensor. Their market share far exceeds that of other sensors. Temperature measurement began in the early 17th century. Powered by semiconductor technology, this century saw the development of semiconductor thermocouple sensors, PN junction temperature sensors, and integrated temperature sensors. Correspondingly, based on the laws of wave-matter interaction, acoustic temperature sensors, infrared sensors, and microwave sensors have been developed.

When two conductors of different materials are connected at a point and this connection is heated, a potential difference develops in the unheated portion of the conductors. The value of this potential difference is related to the temperature of the unheated portion and the materials of the two conductors. This phenomenon occurs over a wide temperature range. By accurately measuring this potential difference and then measuring the ambient temperature of the unheated portion, the temperature of the heated portion can be accurately determined. Because they must consist of two conductors of different materials, they are called "thermocouples." Thermocouples made of different materials are used in different temperature ranges and have varying sensitivities. The sensitivity of a thermocouple refers to the change in output potential difference when the temperature of the heating point changes by 1°C. For most metal-supported thermocouples, this value is approximately 5 to 40 microvolts/°C.

Thermocouple sensors have their own advantages and disadvantages. They have relatively low sensitivity and are susceptible to environmental interference and preamplifier temperature drift, making them unsuitable for measuring small temperature changes. Since the sensitivity of thermocouple temperature sensors is independent of the thickness of the material, they can be made from very fine materials. Furthermore, because the metal materials used to make thermocouples are highly ductile, these delicate temperature-sensing elements have extremely high response speeds, enabling them to measure rapidly changing processes.

Temperature sensors are one of the most commonly used sensors. Modern temperature sensors are extremely compact, making them widely used in various fields of production and providing countless conveniences and functions in our lives.