The bimetal sensing element consists of a strip made up of two thin layers of metal with:

The bimetal sensing element operates based on the principle of thermal expansion, which is the tendency of materials to change shape or size in response to temperature changes. In a bimetal strip, two distinct metals are bonded together. These metals are selected specifically because they have different rates of thermal expansion.

When the temperature changes, one metal expands more than the other. This differential expansion causes the strip to bend or deflect. The curvature or movement of the bimetallic strip can then be utilized in various applications, such as in thermostats or temperature gauges, to provide a mechanical response to temperature changes.

The ability of the bimetal strip to bend is a critical feature that relies on this difference in thermal expansion properties. If the rates of thermal expansion were similar, the strip would not bend effectively and wouldn’t function as a reliable sensor for temperature measurement. This principle of utilizing two differing metals, rather than aspects like specific heat or electrical resistance, makes the bimetallic strip a practical and widely used sensing element in many engineering applications.