Vernier Calliper

The meter scale enables us to measure the length to the nearest millimeter only. Engineers and scientists need to measure much smaller distances accurately. For this a special type of scale called Vernier scale is used.




Vernier Calliper

The Vernier scale consists of a main scale graduated in centimeters and millimeters. On the Vernier scale 0.9 cm is divided into ten equal parts. The least count or the smallest reading which you can get with the instrument can be calculated as under:

Least count = one main scale (MS) division - one vernier scale (VS) division.

= 1 mm - 0.09 mm

= 0.1 mm

= 0.01 cm

The least count of the vernier

= 0.01 cm

The Vernier calliper consists of a main scale fitted with a jaw at one end. Another jaw, containing the vernier scale, moves over the main scale. When the two jaws are in contact, the zero of the main scale and the zero of the vernier scale should coincide. If both the zeros do not coincide, there will be a positive or negative zero error.

After calculating the least count place the object between the two jaws.

Record the position of zero of the vernier scale on the main scale (3.2 cm in figure below).



Principle of Vernier

You will notice that one of the vernier scale divisions coincides with one of the main scale divisions. (In the illustration, 3rd division on the vernier coincides with a MS division).

Reading of the instrument = MS div + (coinciding VS div x L.C.)

= 3.2 + (3 x 0.01)

= 3.2 + 0.03

= 3.23 cm

To measure the inner and outer diameter of a hollow cylinder or ring, inner and outer callipers are used. Take measurements by the two methods as shown in figure below.

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