Caliper is a device employed to measure length; it is suitable to measure (with precision of tenth, twentieth, fiftieth and hundredth of a millimetre) the width of an object, the distance between two flat faces in a concavity, the depth of a groove or hole. Dial caliper is extremely easy-to-use and it ensures immediacy of reading.
On the main body of dial caliper there is a millimetre scale, while on the Vernier there is a dial clock moved by the movement of the Vernier with kinematic mechanisms similar to those used for dial gauges. Therefore, millimetres can be read on fixed scale and on dial clock the corresponding fractions.
Dial clocks are usually made to display 1 or 2 mm in a rotation, with a resolution from 0.05 to 0.02 mm. Dial clocks have often the possibility to be adjusted in order to match the scale zero with an arbitrary position of the pointer; useful to make comparisons between different units, but that requires a preliminary verification of zero position when making absolute measurements.