Air conditioning sensor principle and application Air conditioning sensor principle The temperature sensor used in air conditioning mainly uses a negative temperature coefficient thermistor (also known as NTC thermistor). The temperature sensor is made of manganese, cobalt, nickel, copper and other metal oxides as the main materials, and is made by ceramic technology. These metal oxide materials all have semiconductor properties, because they are completely similar to semiconductor materials such as germanium and silicon in electrical conductivity. When the temperature is low, the number of carriers (electrons and holes) of these oxide materials is small, so the resistance value is high; as the temperature increases, the number of carriers increases, so the resistance value decreases. When the temperature changes, its resistance also changes. As the temperature increases, the resistance value becomes smaller, and as the temperature decreases, the group value increases. For example, the following figure shows the characteristic curves of some tube temperature sensors of a brand.
Air conditioning sensor application There are two types of air conditioning sensors: copper head and plastic head. The main purpose of the copper head sensor is to measure the temperature of the pipeline, and the plastic head sensor is mainly used to measure the temperature of the air. The specific application of the temperature sensor is as follows: The temperature sensor at the bottom of the compressor: It is mainly used to detect the temperature at the bottom of the compressor. The low temperature at the bottom of the compressor may be due to the return of refrigerant, and the temperature is too high due to insufficient refrigerant. Detection control. Exhaust temperature sensor: installed at the exhaust port of the compressor, used to detect the compressor exhaust temperature, in order to control and protect the system. Return air temperature sensor: Detect the return air temperature of the compressor, ensure that the refrigerant returned to the compressor is superheated steam, and prevent the compressor from returning to liquid. Thermal cross temperature sensor: used for outdoor unit condenser and indoor unit evaporator respectively. There are generally two condensers, which are placed at the inlet and outlet respectively. There are generally three evaporators, namely import, middle and export.
