## Vernier Calipers : Measuring Small Lengths

This device uses two scales for the purpose of measurements. Let us see the diagram of a vernier calipers to understand its construction.

**Construction of a vernier caliper**

**Outside jaws or external jaws**: It is used to measure external diameter or width of an object**Inside jaws or internal jaws**: It is used to measure internal diameter of an object**Depth gauge**: It is used to measure depths of an object or a hole**Main scale in mm**: scale marked every mm**Main scale in inches and fractions****Vernier scale**: gives interpolated measurements to 0.02 mm or better**Vernier scale**: gives interpolated measurements in 1/1000 th of an inch**Retainer or stop**:used to block movable part to allow the easy transferring of a measurement

**Principle of the vernier**

“n divisions of the vernier coincides with (n-1) divisions of the main scale.”

The total length of these 10 divisions is equal to the length of (10 – 1 = 9) divisions of the main scale.

Now, length of 9 divisions of main scale = 9 mm

Length of 10 divisions of vernier scale = 10 mm

Therefore, length of 1 divisions of vernier scale = 9/10 mm = 0.9 mm

It means that each vernier division is 1/10 mm = 0.1 mm smaller than a main scale division.

**Least count of a vernier or vernier constant**

Least Count (L.C.) = Value of 1 main scale division – Value of 1 vernier scale division

Let the value of 1 main scale division (M.S.D. = Main Scale Division) be x . Then,

Value of n divisions on vernier ( V.S.D. = Vernier Scale Division) = (n-1) x

Value of 1 division on vernier = \frac{(n-1)x}{n} \

Least Count = 1 M.S.D. – 1 V.S.D.

= x - \frac{(n-1)x}{n} \

= \frac{x}{n} \

**Example :**

*Published on
September 17th, 2020 | by
Abhishek Mandal *