**What is a Vernier Caliper? **A vernier caliper is a caliper consisting of two pieces joined together with one being stationary while the other slides on top of it. The fixed part features a graduated scale while the sliding part has a vernier scale on it. It can also be described as two L-shaped frames joined together with the smaller one able to slide on top of the larger one. Both are graduated along their longer lengths and the dimensions of an object are obtained by measuring the distance between the edges of the shorter arms.

**The Guy Who Invented Vernier Caliper **

*French scientist Pierre Vernier(1580-1637)* is credited with the invention of the Vernier Caliper which is also named after him. Born in 1580 in the city of Ornans in France, Pierre obtained his scientific education from his father and went on to become a mathematician and inventor. The King of Spain also chose him to be the captain and custodian of the castle at Ornans. Later he also served as the director of finance and the councilor of the county of Burgundy.

**Theory of Vernier Caliper:**

The Vernier Caliper is widely used to measure lengths precisely. It contains two graduated scales. A main scale which is graduated similar to a normal ruler and a Vernier scale which can slide along the main scale. The two scales contain a very small relative pitch difference which is responsible for the greater accuracy. If the relative pitch difference is 1/10 then the enhancement factor of any displacement is equal to the inverse of that number i.e 10.

The vernier caliper is mainly used for measuring diameters of objects, both internal and external. The technique for measurement is to first read the main scale to the nearest division. Then the vernier scale is used to measure the distance between the two main scale divisions which provides more accurate measurements.

The Vernier scale is designed in such a way that the distance between each division on the vernier scale is a fraction of that between the divisions on the main scale. **Usually it is so that 10 small divisions on the vernier scale equal 9 small divisions of the main scale.** This way when the zero points of both scales are coincident, the first mark on the vernier scale is one tenth behind the first mark on the main scale. Consequently the second mark is behind by 2/10 and so on. Only the tenth mark will coincide with the markings on the main scale since it is 10/10 i.e one whole unit behind the main scale and it would be coincident with the ninth mark on the main scale.

This is the principle behind the vernier caliper which means that for any distance the division on the vernier scale which coincides with the main scale provides us with the difference of that division with the main scale and allows us to measure distances in decimal points.