Function of a bimetal thermometer
The measuring element consists of two,welded together, metal tapes. The tapes having different coefficients of thermal expansion. The coiled measuring element is fixed at the end of the stem; the other side being connected to the pointer axle.
The bimetal stretches or bends itself in case of a change in temperature, causing the coiled element into a turning movement. This movement is proportional to the change in temperature and is indicated on a dial.
Bimetal thermometers are used for temperatures from – 50°C up to +500 C. Accuracy is ± 1 % of full scale deflection.