Construction and Working Vernier Calipers

Construction and Working Vernier Calipers

This instrument is used to measure thickness, diameter or depth of a body up to 0.1 mm accurately.

Construction

Vernier Calipers consist of a rectangular steel bar whose one side is graduated in centimeters. This scale is known as the main scale (M.S). A small scale consisting of 10 divisions which slides over the main scale is known as the vernier scale (V.S). This instrument has two sets of jaws which enable it to measure the internal and external diameters.

Least Count

The smallest distance which can be measured by vernier calipers is called the “Least Count”.

Least Count = Value of the smallest division on M.S/Total number of division on the V.S

=1mm/10

= 0.1mm

= 0.01 cm

Zero Error

On closing the jaws if the zero of the main scale coincides with the zero of the vernier scale then the instrument has no zero error and no correction is required, otherwise there is an error if the zero of the vernier scale is on the right side of the main scale, the zero error is positive so the distance is to be subtracted from the observed value.

Working

To measure the length of an object, it is placed between the two jaws of the vernier calipers and first the reading of the main scale is noted, then the reading of the vernier scale is taken and added to the main scale reading.