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The principle and control method of electronic thermostat


Control methods generally fall into two; One is controlled by the temperature change of the object being cooled for, more than the steam pressure type temperature controller, another by the control to the change of temperature of the cooling object, use the electronic temperature controller. The thermostat is divided into:

Mechanical is divided into: steam pressure type thermostat, liquid expansion thermostat, gas adsorption type thermostat, metal expansion type thermostat.

The vapor pressure thermostat is divided into: gas type, liquid gas mixed type and liquid type. Home air conditioning mechanical is given priority to with this type of thermostat.

Electronic type can be divided into: resistive temperature controller and thermocouple temperature controller.

The role of the electrical system:

The effect of air conditioning circuit system is to control the air conditioning and multi-function run normally, protect the normal operation of the compressor and fan motors. Circuit system of the main components are: thermostat, thermal protector, master switch, running capacitor, fan motor running capacitor are fixed inside the control box, etc. Left is used by type air conditioner electrical circuit diagram. The effect of temperature controller is just control the start and stop of compressor.

The working principle of

The vapor pressure type

Bellows action in the spring, spring tension is controlled by a knob on the panel, the capillary on the air conditioner indoor air inhaled FengKouChu, react to the indoor cycling return air temperature. When the room temperature rising to the setting temperature, thermal dose of gas expansion of capillary and bellows, bellows elongation and overcome the spring tension connected the switch contact, the compressor operation, refrigeration system, until the room temperature and fell to the set temperature, the heat pack gas contraction, corrugated pipe shrinkage action with spring and puts switch off position, make the compressor motor circuit is cut off. This action repeatedly, so as to achieve the goal of control room temperature.

Electronic temperature controller

Electronic temperature controller (resistive) is a method to measure the thermal resistance, generally USES the white gold, copper, tungsten, and semiconductor (thermistor, etc) as temperature resistance, the resistance have their optimal point. Most household air conditioning sensor based on thermal resistance type.

Thermistor thermostat is made according to the principle of wheatstone bridge, (left) is a wheatstone bridge. On both ends of BD E the power is connected, according to the kirchhoff's law, as the bridge of the resistor R1 * R3 and R4 = R2 potential of two points A and C are equal, the output end there is no current flows through the between A and C, the impedance of the thermal resistor R1 vary with ambient temperature increase or decrease the size of the change, the balance is damaged, between the AC output current. Therefore, when a thermostat, can easily by selecting the appropriate thermistor to change the temperature adjusting range and working temperature

Metal expansion thermostat:

According to the principle of heat bilges cold shrink objects. Heat bilges cold shrink objects are common, but different objects in the degree of heat bilges cold shrink. Both sides of the double piece of gold is a conductor of different material, the change of temperature due to different degrees higher shrinkage and make double gold piece bending, encounter set contact or switch, make setting circuit (protect) begin to work. Temperature control switch, thermostat, thermal protector