Why bimetallic thermometer temperature sensing element is a spiral?

Bimetallic thermometer 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. We in the production of bimetal temperature time, choose the metal ( Is the heat element) Rolled into a spiral. Do you know why? Actually do so, mainly from two aspects: one is the spiral can increase the length of the bimetallic strip to improve sensitivity, 2 it is can be deformation into the center of the coil spring rotation for instructions. For us to know these, bimetallic thermometer, the choose and buy is also a help, because of the temperature sensing element is bimetallic thermometer & other Heart & throughout; 。