双金属片是利用金属体积冷缩热胀的原理，将两种不同膨胀系数的金属片接在一起，当温度变化时，两者之伸长长度不同以致于向一边弯曲，来带动接点，使其接通或开路。

时钟

机械时钟的机械设备对温度的变化敏感，可能会导致钟表不能运转，从而不能正确指示时间，有些部件就会用双金属片补偿这种改变。最常见的方式是将摆轮的轮辋用双金属制成。

温度计

直接显示的度盘式温度计（例如室外温度计或肉类温度计）核心构件即是卷成一盘的双金属片。

A bimetallic strip is used to convert a temperature change into mechanical displacement. The strip consists of two strips of different metals which expand at different rates as they are heated, usually steel and copper, or in some cases steel and brass. The strips are joined together throughout their length by riveting, brazing or welding. The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial temperature. The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled