Working Principle of Mechanical Thermometer!
The pointer Thermohygrometer works on the principle that two different metals expand differently when the temperature changes. The main component is a multi-layer metal sheet consisting of two or more metal sheets laminated together. In order to improve the sensitivity of temperature measurement, metal sheets are usually made into spiral coils. When the temperature of multi-layer metal sheet changes, the expansion or shrinkage of each layer of metal varies, making the spiral roll up or loosen. Because one end of the spiral coil is fixed and the other end is connected with a freely rotating pointer, the pointer can indicate the temperature on a circular scale when the bimetal sheet senses the temperature change.