April 08, 2021
Vernier scales can be used on microscopes, stereotaxic frames and micromanipulators. The vernier scale was invented by French mathematician Pierre Vernier in 1631 as an upgrade on Pedro Nunes' measurement system for precision astrolobes. With a main scale and a sliding secondary scale, a vernier is used for making precise measurements.
How a Vernier Scale Works
The vernier scale is marked with divisions slightly smaller than the divisions of the main scale. For example, a vernier scale could have 11 markings for every 10 on the main scale. That's 10 divisions on the vernier scale for every 9 on the main scale. This means that the vernier divisions are each 90% of the main scale divisions. In this case, the 0-line and the 10-line on the vernier could pair up with marks on the main scale, but none of the other divisions on the vernier would match a line of the main scale. For example, the 0 and 10-lines of the vernier scale could pair up with the 0 and 9-lines on the main scale. If the 0-line pairs up with a mark, the first division of the vernier (1 mark) would be 10% short of reaching a mark of the main scale, the second division (2 mark) would miss a mark on the main scale by 20%, the third division (3 mark) would miss a mark on the main scale by 30%, etc.
How to Read a Linear Vernier Scale
Follow these steps to read the vernier scale:
Read the main scale. Look for the last whole increment visible before the 0 (zero) mark.
Read the secondary scale (Vernier) measurement. This is the division tick mark that lines up best with a mark on the main scale.
Add the two measurements together.
The image at the right shows a linear scale. The 0 on the vernier scale lines up with the 4 on the main scale. Notice that the 10 on the vernier scale also lines up with a mark on the main scale (4.9). We ignore the second mark that lines up. So, the measurement shown is 4.00mm.