How many control modes does the electronic thermostat have

Release Time:

2020-07-15

There are generally two control methods; one is controlled by the temperature change of the object to be cooled, mostly using a vapor pressure temperature controller, and the other is controlled by the temperature difference of the object to be cooled, mostly using an electronic temperature controller. controller. Thermostats are divided into: Mechanical type is divided into: vapor pressure thermostat, liquid expansion thermostat, gas adsorption thermostat, metal expansion thermostat. Among them, the vapor pressure thermostat is divided into: inflatable type, liquid-gas mixed type and liquid-filled type. The mechanical type of household air conditioner is mainly based on this type of thermostat. Electronic type is divided into: resistance thermostat and thermocouple thermostat. The role of the circuit system: The function of the air conditioner circuit system is to control the normal and multi-functional operation of the air conditioner, and to protect the normal operation of the compressor and fan motor. The main components of the circuit system are: thermostat, thermal protector, main control switch, running capacitor, fan motor running capacitor, etc. are fixed in the control box. The picture on the left is the electrical wiring diagram of the single cooling air conditioner. The role of the temperature controller is only to control the start and stop of the compressor. working principle steam pressure The action of the bellows acts on the spring, and the spring force of the spring is controlled by the knob on the control panel. The capillary is placed at the air outlet of the air conditioner indoors and responds to the temperature of the indoor circulating return air. When the room temperature rises to the set temperature, the temperature-sensing agent gas in the capillary tube and the bellows expands, making the bellows stretch and overcoming the elastic force of the spring to turn on the switch contacts. At this time, the compressor runs and the system cools down until room temperature. When the temperature drops to the set temperature again, the gas of the temperature sensing package shrinks, the bellows shrinks and acts together with the spring, and the switch is placed in the off position to cut off the motor circuit of the compressor. This action is repeated to achieve the purpose of controlling the room temperature. Electronic temperature controller The electronic temperature controller (resistance type) is measured by the method of resistance temperature sensing. Generally, platinum wire, copper wire, tungsten wire and semiconductor (thermistor, etc.) are used as temperature measuring resistors. These resistors have their own advantages and accuracy. point. Most of the sensors of household air conditioners are of thermistor type. The thermistor thermostat is made according to the principle of Wheatstone bridge, (left picture) is a Wheatstone bridge. Connect the power supply E at both ends of BD. According to Kirchhoff's law, when the resistance of the bridge is R1×R4=R2×R3, the potentials of A and C are equal, and no current flows between the output terminals A and C. , The size of the resistance R1 of the thermistor changes with the rise or fall of the surrounding temperature, so that the balance is destroyed, and there is an output current between AC. Therefore, when composing a thermostat, it is easy to change the temperature adjustment range and operating temperature by selecting an appropriate thermistor Metal expansion thermostat: According to the principle of thermal expansion and contraction of objects. Thermal expansion and contraction are common to objects, but different objects have different degrees of thermal expansion and contraction. The two sides of the double gold piece are conductors of different materials. Under the changing temperature, the double gold piece is bent due to the different degree of expansion and contraction. When it touches the set contact or switch, the set circuit (protection) starts to work. Thermostat switch, thermostat, thermal protector