French mathematician Pierre Vernier invented the vernier scale in 1631. The main use of the vernier calliper over the main scale is to get an accurate and precise measurement.
The least count of vernier callipers is also known as the vernier constant. It is defined as the difference between one main scale division and one vernier scale division.
It is mathematically given as:
|VC = 1 MSD – 1 VSD|
When there are n divisions on the vernier scale which coincides with (n-1) division on the main scale, then the least count of vernier calliper is:
Therefore, the least count of vernier calliper is 0.1 mm.
Zero error is defined as the condition in which the measuring device registers a reading when there should not be any reading.
The zero error of vernier calliper is calculated as:
Actual reading = Main scale + Vernier scale – (Zero error)
There are two types of zero error:
If the jaws of the vernier callipers are in contact with each other, then determine the zero error of the vernier calliper if the VSD is 3.
The jaws of the vernier calliper are in contact with each other.
Therefore, the least count of the vernier calliper is given as:
LC = MSD – VSD
LC = 1 – (9/10) = 0.1 mm
The main scale reading, MSR = 0 mm
The vernier scale reading, VSR = 3
Zero error = MSR + VSR x LC
Zero error = 0 + 3 x 0.1 = 0.3 mm