Electronic temperature controllers are divided into resistance type temperature controllers and thermocouple type temperature controllers.
The function of the circuit system:
The main components of the circuit system include: temperature controller, thermal protector, main control switch, operating capacitor, fan motor operating capacitor, etc., which are fixed in the control box. The left figure shows the electrical circuit diagram of a single cooling air conditioner. The function of the temperature controller is only to control the start and stop of the compressor.
operational principle
Electronic temperature controller
Electronic temperature controllers (resistive) are measured using the method of resistance temperature sensing. Generally, platinum wire, copper wire, tungsten wire, and semiconductors (thermistors, etc.) are used as temperature measuring resistors, each of which has its own advantages. The sensors of household air conditioners are mostly thermistor type.
The thermistor type temperature controller is made based on the principle of a Wheatstone bridge and is a Wheatstone bridge. Connect power supply E at both ends of BD, and according to Kirchhoff's law, when the resistance of the bridge R1 × R4=R2 × At R3, the potentials of A and C are equal, and there is no current flowing between the output terminals A and C. The impedance R1 of the thermistor changes with the increase or decrease of the surrounding temperature, causing the balance to be disrupted, and there is an output current between AC. Therefore, when constructing a temperature controller, it is easy to change the temperature adjustment range and operating temperature by selecting appropriate thermistors.