How do I read a manual vernier caliper?
Calipers are precision instruments that can measure both internal and external ranges/distances with very high accuracy. The measurement results are interpreted by the operator using the instrument scale. Manual calipers have two scales, the main scale and the vernier. Compared to digital calipers, no battery is needed here, but reading and interpreting the measured value is more difficult.
To measure the outer dimensions of an object, the object is placed in the outer legs. The legs are pushed together until the object is held.
The first significant digit is read from the main scale, immediately to the left of the "zero" on the vernier scale. In the example shown, this is 23.