What is the working principle of bimetal thermometer?

Bimetal thermometer is a kind of instrument which can directly measure the middle and low temperature of a medium. Its working principle is based on the principle of solid thermal expansion, and two pieces of metal sheets with great difference in expansion coefficient are welded together. When the temperature changes, the different expansion coefficient results in different expansion and contraction, resulting in the bending deformation of the metal sheet. According to the different deformation, different rotation amount is generated. The rotation amount drives the connected rotating shaft and the indicator needle at the other end to indicate the temperature. Therefore, the temperature sensing element of bimetallic thermometer is particularly important. Then do you know the principle of temperature sensing element of bimetal thermometer?

BThe working principle of bimetal thermometer is that the expansion coefficient of the two metals is different. When the temperature changes, the length of the two metals will change differently. When the two metals are bonded together, the shape will be bent. If a metal with the same coefficient of expansion is used, the length of the sheet metal will not bend and the temperature will not be measured.