Bimettalic Thermometer

A Bimetallic thermometer consists of bimetallic strip . Bimetallic strip consist of two pieces of different metals firmly bonded together by welding . Different two materials having different coefficient of thermal expansion . Bimetallic strip is wound in the form of helix or in spiral form . Its one end is fixed permanently to outer casing to form stopper and other end is connected to pointer .

               When different strip is fixed at one end heated from free end then it bends in the direction of material having low thermal coefficient of expansion . The bending movement of free end is connected to pointer which moves on calibrated scale .

   ADVANTAGES :-

1)      Its construction is very simple.

2)      No maintenance is required.

3)      Capability to work under greatly over range condition without harm.

4)      It’s cost is very low .

DISADVANTAGES :-

     1)      Material is subjected to creep at very high temperature.

     2)      Speed of response is very low .

APPLICATIONS :-

     1)   This type of thermometer used in switching devices in domestic like ovens , electric irons , and refrigerators .

     2)      Thermometer are used in various applications in chemistry lab.

     3)      It is also useful in medical applications .