Temperature is a fundamental physical quantity, and all processes in nature are closely related to temperature. Temperature sensors are the earliest developed and most widely used type of sensor. The market share of temperature sensors greatly exceeds that of 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. Correspondingly, based on the interaction law between waves and matter, acoustic temperature sensors, infrared sensors, and microwave sensors have been developed successively.

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. The sensitivity of a thermocouple refers to the change in output potential difference when the heating point temperature changes by 1 ℃. For most metal supported thermocouples, this value is approximately between 5-40 microvolts/℃.

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, even very fine materials can be used to make temperature sensors. Due to the excellent ductility of the metal materials used to make thermocouples, this delicate temperature measuring element has a very high response speed and can measure rapidly changing processes.

Temperature sensors are the most commonly used among various types of sensors. Modern temperature sensors have a very small appearance, which makes them widely used in various fields of production practice and provides countless conveniences and functions for our lives.

There are four main types of temperature sensors: thermocouples, thermistors, resistance temperature detectors (RTDs), and IC temperature sensors. IC temperature sensors include two types: analog output and digital output.