双金属是由两个不同金属(例如钢和锌)连接的条带制成的组件。每种金属都有固定的热膨胀系数，每种金属的热膨胀系数不同。因此，当温度发生变化时，这将导致每种金属产生不同的膨胀，从而使双金属弯曲。由于热膨胀系数已知，因此可以根据双金属中引起的弯曲量来判断温度。因此，在双金属表盘温度计中，双金属通过机械测量系统与指示刻度盘上温度的指针相连。

　　A bimetal is a component made of two connected strips of different metals (e.g. steel and zinc). Every metal has a fixed thermal expansion coefficient, which is different for each metal. Thus, when the temperature changes, this will cause a different expansion in each metal, which bends the bimetal. As the thermal expansion coefficient is known, it is possible to tell the temperature from the amount of bending caused in the bimetal. Therefore, in a bimetal dial thermometer the bimetal is connected, via a mechanical measuring system, with a pointer indicating the temperature on a graduated disc.