The working principle of bimetallic thermometer temperature sensing element is what?

Bimetallic thermometer is a kind of can direct measurement of cold spot temperature instrument, its working principle is based on the principle of solid heat expansion, the two pieces of expansion coefficient difference is very big pieces of metal welded together. When the temperature changes, the difference is very big, caused the different expansion coefficient of expansion and contraction, the deformation of sheet metal bending. According to different deformation and produce different momentum, momentum to drive the connection shaft and the other end of the indicating needle, indicate the temperature. Thus, bimetallic thermometer temperature sensing element is especially important, then you know the bimetallic thermometer by principle of thermal components? The working principle of bimetallic thermometer temperature sensing element is of two kinds of metal expansion coefficient is different, when the temperature changes, the change will be different for the length of two metals, and two kinds of metal stick together, can produce bending shape. If use the same kind of expansion coefficient of metal, the temperature changes, the change of the length of the same, won't produce bending sheet metal, will not be able to measure temperature.