1. The working principle of the snap action temperature controller switch is that the bimetallic disc of the temperature sensing element is preformed at a certain temperature. When the ambient temperature changes, the bending degree of the disc will change. When the bending reaches a certain degree, the circuit will be connected (or disconnected) to make the refrigeration (or heating) equipment work.

 

2. Thermal bimetals are composite functional materials with shape changes with temperature, which are composed of two or more metals or alloys with different expansion coefficients along the entire contact surface.

 

3. In the component alloys of thermal bimetals, the component alloy layer with higher expansion coefficient is generally called active layer or high expansion layer (HES). The component alloy layer with low expansion coefficient is called passive layer or low expansion layer (LES). The interlayer with different thickness is added between the active layer and the passive layer as the conductive layer, which generally includes pure Ni, pure Cu, zirconium copper, etc. It is mainly used to control the resistivity of thermal bimetals to obtain a series of resistive thermal bimetals with basically the same thermal sensitivity but different resistivity.

 

4. Invar alloy (also known as invar), also known as "unchanging steel", is a nickel iron alloy. Its composition is 36% nickel, 63.8% iron, and 0.2% carbon. Its coefficient of thermal expansion is extremely low, and it can maintain a fixed length in a wide temperature range. It was first discovered by Swiss physicist C. E. Guillaume in 1896. It is mainly used to manufacture standard ruler, thermometer, rangefinder, clock and watch swing wheel, block gauge, resonant cavity of microwave equipment, gravimeter, thermal bimetal component materials, optical instrument parts, etc. Bimetal is usually used as passive layer in thermostat.