Temperature is a physical quantity that characterizes the degree of heat and cold of an object, and is a very important and common measurement parameter in the process of industrial and agricultural production. Temperature measurement and control to ensure product quality, improve production efficiency, energy saving, production safety, and promote the development of national economy plays a very important role. Due to the universality of temperature measurement, the number of temperature sensors in a variety of sensors in the first place, accounting for about 50%.
Temperature sensors are indirectly measured by the object with the temperature change and change a certain characteristic. Many materials, components of the characteristics of the temperature changes with the change, so the material can be used as a temperature sensor is quite a lot. Temperature sensor with the temperature and cause changes in physical parameters: expansion, resistance, capacitance, and electric potential, magnetic energy, frequency, optical properties and thermal noise and so on. With the development of production, new temperature sensors will continue to emerge.
Because of the industrial and agricultural production in the temperature measurement range is extremely wide, from minus a few hundred degrees to zero on a few thousand degrees, and a variety of materials made of temperature sensors can only be used in a certain temperature range.
Temperature sensors and the measured medium of contact is divided into two categories: contact and non-contact. Contact temperature sensors need to maintain thermal contact with the measured medium, so that the two are sufficient heat exchange to achieve the same temperature. This category of sensors are mainly resistive, thermocouple, PN junction temperature sensors. Non-contact temperature sensors do not need to be in contact with the measured medium, but through the measured medium of thermal radiation or convection to the temperature sensor, in order to achieve the purpose of temperature measurement. This category of sensors are mainly infrared temperature measurement sensors. The main feature of this method of temperature measurement is that it can measure the temperature of the state of motion material (such as the slow exercise of the train bearing temperature, the temperature of the rotating cement kiln) and small heat capacity of the object (such as integrated circuits in the temperature distribution).