For a long time, in the electronics industry, thermostats are developing rapidly. Because it can flexibly control the start-stop and indoor temperature of air-conditioning units in various regions, and can save construction space and project cost, the fan coil unit (FCU) plus fresh air air-conditioning system has always been a hotel and restaurant mainly engaged in the rental of guest rooms and business methods. It is the type of semi-centralized air-conditioning system that is widely used in buildings such as office buildings. The room air conditioner thermostat is the key to control the terminal device - fan coil unit (FCU) for cooling/heating, and to achieve room temperature control and energy-saving operation.

        The ordinary fan coil air conditioner thermostat is basically an independent closed-loop temperature adjustment system, which is mainly composed of a temperature sensor, a two-position controller, a temperature setting mechanism, a manual three-speed switch and a hot and cold switching device. The control principle is that the air conditioner thermostat generates a two-position control signal according to the comparison result of the room temperature measured by the temperature sensor and the set value, and controls the switch of the electric water valve (two-way valve or three-way valve) of the cold and hot water circulation pipeline, namely Adjust the supply air temperature (cooling capacity) by cutting and opening the water circulation in the coil.

        The first-generation air conditioner thermostat is mainly an electrical product. The temperature sensor of the air conditioner thermostat adopts a bimetallic sheet or a pneumatic temperature bulb. The temperature is set by adjusting the pre-tightening force through the "given temperature plate", and the fan three-speed switch and The season switch is a splash-type mechanical switch. Such air-conditioning thermostat products generally have problems such as "the temperature setting index value is too coarse", "the time constant is too large", and "the mechanical switch is easily damaged".

        The first-generation air conditioner thermostat is an electronic product. The temperature sensor adopts thermistor or thermal resistance. The temperature setting and fan speed switch of some products realize the human-computer interaction interface through touch keys and liquid crystal display, and the hot and cold switching is automatically completed. The operational amplifier circuit and switch circuit realize two-bit adjustment. This type of intelligent air-conditioning thermostat product improves the human-computer interaction interface and solves the problems of "the temperature setting is too coarse", but there are still "low control accuracy", "large time constant" and "complex operation". "And other issues.

        At present, domestic and foreign manufacturers are researching and developing the third-generation intelligent room temperature air conditioner thermostat. Each manufacturer actively responds to national policies and applies new control models and numerical control chips to achieve intelligent control. At present, domestic manufacturers have produced intelligent room temperature air conditioner thermostats, which have been applied to practical projects. This production drives the development of the electronics industry.