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 ± 1,6% of full scale deflection.