The bimetal element consists of two metals with significantly different thermal expansion coefficients bonded together and formed into strips or coils. It bends with temperature changes. The sensing element is a multi-turn helical bimetal strip with one end fixed and the other (free end) connected to a spindle.
For axial types, the pointer is directly mounted on the spindle. For radial, 135° and universal types, the pointer is connected via a spring coupling mechanism. When temperature changes, the free end of the sensing element rotates, driving the spindle and pointer to indicate the measured temperature on the dial.
In the electrical contact version (including explosion-proof types), adjustable contacts are mounted on the pointer. When the temperature reaches or exceeds the set value, the contacts close to trigger alarm or control actions. Contact ratings are 10VA (non-inductive load), with working voltage of 220V or 380V and maximum current of 1A.
The remote-transmission type combines a mechanical bimetal thermometer with an RTD, thermocouple, or temperature transmitter, enabling both local indication and remote signal transmission to a control room.