Bimetallic Strip Thermometer
Every metal and alloy has its won coefficient of expansion. That means they are expanded in their size differently for same temperature increase. If we couple two strips made of two different metals or alloys, then due to dissimilarity in coefficient of expansion they will be expanded or contracted differently during temperature change and consequently the whole bimetallic strip assembly will bend or be deformed. As this deformation of shape of a specific bimetallic strip is due to temperature rise or fall, this deformation can also be measured in the scale of temperature. From this principle, the concept of Bimetallic Strip Thermometer came.
Bimetallic strip mainly used in industries in temperature control devices. It is assembled with temperature controller system. When temperature reaches to a preset value, the bimetallic strip is so bent it closes an NO contact which initiates the cooling system to decrease the temperature of the system. Bimetallic strip thermometer is also widely used in industries because of their simplicity and robustness.
There are mainly two types of bimetallic strip thermometer are available in the market. Both are same in working but differ in construction.