# What is a Vernier Caliper?

If there is one indispensable device that you would find in any physics lab or engineering application, that would be the Vernier calipers. Used for measuring linear dimensions, the internal and external diameters of objects, Vernier calipers consist of a pair of jaws where the top jaw is attached to a fixed scale also known as the main scale and the lower jaw is attached to a sliding scale which is also known as the Vernier scale. The Vernier scale moves over the main scale.

The smaller jaw is used to measure the internal diameter of objects, while the larger one is used to measure the external diameter.

Both the main scale and the Vernier scale are etched with indentations – inches on one side and centimetres on the other side. The inches and centimetres have smaller divisions in between them. However, the indentations on the Vernier scale or the sliding scale signify 1/10th of the smallest division in comparison to the main scale.

French mathematician Pierre Vernier invented the Vernier scale in 1631.

## Why use a Vernier caliper?

Scales cannot measure objects smaller than 1 mm, and this is where a Vernier caliper becomes handy. As the vernier caliper has two scales, both can be used to measure extremely small lengths, as low as 0.1 mm.

The Vernier reading or resolution refers to the smallest distance that a Vernier caliper can measure. Imperial vernier calipers have a resolution of 0.001 inch, while metric Vernier calipers have a resolution starting from 0.02 millimetres.

## How to measure with Vernier calipers?

To measure the width of an object, place the object between the jaws of the caliper. Then move the sliding jaw until the object is gripped firmly between the jaws.

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Now, find where the 0 mark of the vernier scale lines up on the main scale. Let us assume the 0 mark is between 2.2 and 2.3 cm. So, the first reading is 2.2 cm.

The next step is to find the mark on the vernier scale that most closely lines up with one of the marks on the main scale. Let us assume it is at 8.5. As the value is the number of hundredths of centimetres (or tenths of millimetres), the second reading is 0.085 cm.

Add the two values together to get the total reading: 2.2 cm + 0.085 cm = 2.285 cm

### While using a Vernier caliper:

• You need to check whether the zero mark on both scales coincide when the two jaws are in contact. If the zero of the main scale and the zero of the Vernier scale do not coincide, there will be an error in the reading.
• Keep the object clean: Calipers measure at a very minute level, so even a little bit of dirt or grease can cause an error and ruin the entire process.
• The locking screw should be loosened: The screw prevents the device from moving when not in use. By turning the screw clockwise, it loosens and by turning it anticlockwise, it tightens.

Other than the traditional vernier calipers, digital vernier calipers are also available. Though more accurate, digital Vernier calipers are more accurate.