What is the measuring principle of vernier caliper in the small-scale production kit of science and technology?

Vernier calipers use the difference between the line spacing on the main scale and the line spacing on the vernier scale to read out the decimal part. For example, the line spacing on the main scale is 1 mm, and there are 10 grids on the vernier scale with a line spacing of 0.9 mm. When their zero lines coincide, if the vernier scale moves 0.1 mm, its first line coincides with the first line of the main scale. If the vernier scale moves 0.2 mm, its second scribe line coincides with the second scribe line of the main scale.

By analogy, the decimal part of the value can be read from the overlap between the vernier scale and the scribed line on the main scale. The difference between the main scale and the vernier scale is 0.1 mm, which is the minimum reading value of vernier caliper. The vernier principle was put forward by French P. Verniere in 1631. It is often used in the subdivision reading mechanism of length and angle of length measuring tools.