Question

Explain the principle on which vernier instruments are made to enhance accuracy of measurements.

Answer 1

The principle of vernier is that when two scales or divisions slightly different in size are used,
the difference between then can be utilised to enhance the accuracy of measurement. The vernier
caliper essentially consists of two steel rules and these can slide along each other. One of the scales,
i.e., main scale is engraved on a solid L-shaped frame. On this scale cm graduations are divided
into 20 parts so that one small division equals 0.05 cm. One end of the frame contains a fixed jaw
which is shaped into a contact tip at its extremity.
The three elements of vernier caliper, viz. beam, fixed jaw, and sliding jaw permit substantial
improvements in the commonly used measuring techniques over direct measurement with line
graduated rules. The alignment of the distance boundaries with the corresponding graduations of
the rule is ensured by means of the posi-
tive contact members (the jaws of the
caliper gauges). The datum of the meas-
urement can be made to coincide precise-
ly with one of the boundaries of the
distance to be measured. The movable
jaw achieves positive contact with the
object boundary at the opposite end of
the distance to be measured. The closely
observable correspondence of the refer-
ence marks on the slide with a particular
scale value, significantly reduces the ex-
tent of read-out alignment errors.