Definition of the vernier caliper
What is a vernier caliper ? A vernier caliper is a measuring instrument which can make inside, outside, or depth measurements. The vernier scale on it is marked in both British Imperial and metric divisions. The vernier scale has a stationary scale and a movable scale, in this case the vernier bar to the vernier plate. The length is read from the vernier scale.
The movable scale on the vernier caliper is parallel to the fixed scale. These high precision measuring instruments are able to measure outside and inside diameters and most will even measure depth. There are both Imperial and metric scales. The main scale of the caliper is divided into 10 parts, each equal to 0.100 inch. The area between the 0.100 marks is divided into four. Each of these divisions is equal to 0.025 inches.
There are 25 divisions on the vernier scale, each one representing 0.001 inch. Measurement readings are taken by combining the main and vernier scales. Only one division line on the main scale will always line up with a line on the vernier scale. This is the basis to ensure accurate measurements.
To read the caliper, locate the line on the main scale that lines up with the zero (0) on the vernier scale. If the zero lined up with the 1 on the main scale, the reading would be 0.100 inches. If the zero on the vernier scale does not line up exactly with a line on the main scale, then look for a line on the vernier scale that does line up with a line on the main scale.