The Vernier caliper is an extremely precise measuring instrument; it is used to measure internal and external distances extremely accurately – the error may be as little as 0.05 mm – depending on the make.The VERNIER is a small movable graduated scale for obtaining fractional parts of subdivisions on a fixed main scale of any measuring instrument. With a normal scale we may be able to measure down to 0.50 mm or so, while with a vernier scale the least count may be 0.10 mm. Usually vernier calipers have both imperial (inches) and metric (mm) scales.
A vernier caliper is a precision measuring tool. It can be used for three types of measurements, outside distance (such as the length of an object) , inside distance such as the width of a groove or the diameter of a large hole, and depth, such as the depth of a hole or the height of a step.
Vernier calipers come in many sizes. A common type measures 0 to 6 inches.
Modern calipers are digital – in the sense it has an LCD display on which the reading appears – there is no possibility of human error in reading the scale.
The smallest vernier caliper that can be bought off-the-shelf is 150 mm – meaning the jaws open to a maximum of 150 mm. The largest ones go up to 2000 mm.