Vernier Scale:

Vernier scale having a primary scale, which fully divided into minor divisions, and such Vernier having graduations derived from the primary scale graduations. It is identified either direct Vernier or retrograde Vernier. In the first case (n + 1) Vernier; whereas, (n - 1) division on primary scale are divided into n equivalent divisions in the direct Vernier scale. During either case, the variation among one major scale division or one Vernier scale division is equivalent to 1/n and is acknowledged as the least count of the Vernier. The variation between two major scale divisions and two Vernier scale divisions is 2/n.