What is Vernier Scale?

Suppose you are measuring with a caliper, then you suddenly get quite confused. You ask, “Why must the aligned line that gets counted on the vernier scale? How that could be?” If you are in a situation like this, this is a good chance to learn it.

Vernier scale is the secondary scale that is set parallelly next to the main scale to provide higher accuracy. The way it acts is by dividing each division on the main scale into some more smaller divisions.

It is used in both calipers and micrometers. In calipers, it’s found in vernier calipers. While in micrometers, there are only found in some mechanical micrometers to amplify the reading of thimble scale. The presence of the vernier scale is a sign of improved accuracy. Hence, when you buy a new micrometer, a vernier scale should be one thing you take into account. The vernier is also used in other instruments such as theodolites and sextants. However, people today easily find vernier scale on vernier calipers.

The vernier applies both in a linear and circular scale model. While the linear can be found on calipers and micrometers, you’ll find the circular one on the instrument such as theodolite.

He is Pierre Vernier (1580-1637), a French mathematician and inventor, who found the vernier scale in 1631. But, the term vernier was popularized by a French Astronomer, Jérôme Lalande (1732–1807). Thanks, bud!

The mechanism of its working is brilliant. In the end, you will realize as if it has an amplification effect. This mechanism lets you easily solve the problem of measuring where a 1 mm is too narrow to print the friction marks.

How Does It Work?

When it measures nothing, mark 0 on both the vernier and the main scale are aligned perfectly. Then, when the vernier scale slides slowly per one resolution, you’ll find the second mark after 0 on the vernier scale will line up to one mark on the main scale. You slide again, then it’s the turn of the third mark of vernier scale which aligns up with one mark on the main scale.

Look at the scale carefully, the mark 0 on the vernier scale moves very slightly toward one division on the main scale. On the other hand, the aligned marks move alternately to the next right direction. Each time the aligned mark adjust to the right, it is equal to the resolution or the least count of the vernier scale.

Least Count of Vernier Scale

What is the least count? Least count or also refer to resolution is the smallest increment that a particular scale provides. The least count calculation is obtained by simply subtracting one division of the main scale by one division of the vernier scale.

Least Count (LC) = 1 Main Scale Division (MSD) – 1 Vernier Scale Division (VSD)

For example, one division on the main scale values 1mm and one division on the vernier scale is 0.9mm, then the least count is 0.1mm. Similarly, 10mm is the interval of one division of vernier, 9mm is the interval of one division of the main scale, then the least count is 1mm.

Designing A Vernier Scale

We are going to make a vernier scale that has .1mm resolution. However, there are only 10 divisions available on the main scale and the interval of those 10 divisions is 1 cm. Suppose we want the vernier has 10 divisions as well. How long the vernier interval of those 10 divisions must be?

Least Count (LC) = 1 Main Scale Division (MSD) – 1 Vernier Scale Division (VSD)

.01 cm = (1 cm / 10 divisions) – ( x cm / 10 divisions )

x = 9/10 cm = .9cm

As the answer shows, we need to a vernier scale that has .9cm interval with 10 divisions on it in which each division is .09cm (.9mm) in length.