A vernier is an auxiliary scale, invented by Pierre Vernier, which enables the reading of the smallest divisions of a graduated scale. It is important in theodolites, sextants and the mountings for telescopes for accurate determination of angular positions.

Vernier and Main Scale
The scale is read by first taking note of where the zero mark on the vernier scale falls on the main scale. This is the number of complete divisions on the main scale. This is the whole number that should be noted. The fraction or decimal is then read from the vernier scale. This number is taken as the line on the vernier scale that aligns with any line on the main scale (see the two following examples).

Reading 3.3
This reads 3.3

Reading 5.6
This reads 5.6

See also: Height Gauge, Micrometer, Vernier Caliper.

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Subjects: Mechanical Engineering