Please explain this.

Dear Student,
Vernier Calliper

For measuring length accurately, Vernier calliper is used. Vernier calliper was invented by Pierre Vernier. It has accuracy up to 0.01 cm.

Essential Parts:

1. Main Scale

It is a thin long strip of steel on which a scale in engraved in mm. The main scale is generally 15 cm long.

2. Vernier Scale

It is a small movable scale, which slides along the main scale. It has 10 divisions adding up to 9 mm length.

3. External jaws

J ₁ and J ₂ are called external jaws because they are used for measuring external dimensions.

4. Internal jaws

J ₃ and J ₄ are collectively called internal jaws and are used for measuring internal dimensions of a hollow object.

5. Tail

It is at the end of main scale and slides along with the Vernier scale.

When jaws J ₁ and J ₂ are closed, the zero mark of the main scale coincides with that of the Vernier scale and 19 ^thmain scale divisions coincide with 20 ^th Vernier scale divisions.

Terms and Definitions:

• Pitch

The smallest value of length, which can be acquired directly from the main scale accurately, is called pitch.

• Least Count

The magnitude of the smallest measurement, which can be measured by an instrument accurately, is called its least count.

Formula for measuring a length

Length of an object is found by using the formula,

Length = (Pitch × Main Scale Division) + (Least Count × Vernier Scale Division)

If the zeroes of M.S. and V.S. do not coincide, then the instrument is said to have a zero error.Zero Error of Vernier Calliper

1. Positive Zero Error

If the zero mark of the Vernier scale lies on right hand side of zero mark of the main scale, then the error is said to be positive and correction is said to be negative.

Correction = −Coinciding division of V.S. × L.C.

This correction has to be added to the measured length.

2. Negative Zero Error

If the zero mark of the Vernier scale lies on left hand side of zero mark of the main scale, then the error is said to be negative and correction is said to be positive.

Correction = ( n − Coinciding division of V.S.) × L.C.

Where, n is the total number of Vernier scale divisions

 

Regards