Three control states of ntc temperature control switch

　　1. Steam pressure temperature control switch

　　The action of the bellows acts on the spring, and the elastic force of the spring is controlled by the knob on the control panel. The capillary is placed at the air outlet of the indoor air intake of the air conditioner 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, so that the bellows stretches and overcomes 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.

　　2. Electronic temperature control switch

　　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 disadvantages. . 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

　　3. 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.

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