A thermostat is a device that directly or indirectly controls one or more heat and cold sources to maintain a required temperature. To achieve this function, the thermostat must have a sensitive element and a converter, and the sensitive element measures the change in temperature and produces the desired effect on the converter. The converter converts the action from the sensitive element into an action that can be properly controlled in a device that changes temperature. It can be manufactured by CNC engraving, Sand Casting, transparent acrylic(PMMA/PC) 3D Printing.

The most commonly used principle of sensing temperature change is (1) the expansion rate of two different metals combined together (bimetallic sheets) is different; (2) The expansion of two different metals (rods and tubes) is different; (3) expansion of liquid (sealed capsule with external temperature measuring bubble, sealed bellows with or without external temperature measuring bubble); (4) The saturated vapor pressure of the liquid-vapor system (pressure capsule); (5) Thermistor element.

The most commonly used converters are (1) switching switches that turn on or off the circuit; (2) A potentiometer with a vernier driven by a sensitive element; (3) electronic amplifier; (4) Pneumatic actuator.

The most common use of a thermostat is to control room temperature. Typical uses are: control gas valve; Control the fuel furnace regulator; Control electric heating regulator; Control refrigeration compressor; Control gate regulator.

Room temperature regulators can be used to provide a variety of control functions, for example, heating control; Heating - cooling control; Day and night control (the night is controlled at a lower temperature); Multistage control, can be one or multiple heating, one or multiple cooling, or a combination of multistage heating and cooling control.

There are generally several types of thermostats: plug-in - the sensitive element is inserted into the pipeline when it is installed above the pipeline; Immersion - The sensor is immersed in the liquid in the pipe or container to control the liquid; Surface type - The sensor is mounted on the surface of the pipe or similar surface.