# Confused as to how to read this caliper

Here is a picture of a caliper that I found:

Calipers are such basic tools, but I have trouble understanding how they work. Here the main scale says "mm" at the end, and the Vernier scale says "0.05mm". I've read some explanations saying that if the Vernier constant is, say, 0.1, on the Vernier scale the "1" is at a distance of 9/10 from 0, so that if an object that is 0.1mm thick is measured, the "1" on the Vernier scale is moved 1/10 to the right and the "1" is aligned with the "1" on the main scale, and therefore the measurement is taken to be 0.1mm.

But here we have a Vernier scale with 0.05mm as the constant. Shouldn't this mean that the "1" of the Vernier scale should be 0.05mm short of the "1" on the main scale? But this is clearly not the case, the "1" spacing is clearly much larger than the "1" spacing on the main scale. So how does this caliper function?

## 3 Answers

The spacings are larger just to make it easier to read and make more room for the numbers 0 … 10 on the Vernier scale.

The marks on the Vernier scale correspond to 0.00, 0.05, 0.10 … 1.00 mm. For example, when the mark labeled "2" lines up with a tick mark on the main scale, you add 0.20mm to the main scale reading.

It doesn't matter which tick mark on the main scale the "2" lines up with. Obviously the "2" mark will line up with different marks if you measure objects with size 0.20 mm, 1.20 mm, 2.20 mm, etc. The essential point is that only the Vernier scale "2" mark will line up with any mark on the main scale for an increment of 0.20mm.

The problem with most analog meters and measuring devices is you have no feedback on your reading to confirm you are correct.

This site explains how the vernier caliper works in detail, but more importantly has an interactive applet at the bottom. You can move the caliper and it provides the reading. The magnifying glass allows you to zoom in.

The 0 marker gives you the first two digits. Where the movable arm aligns exactly with the fixed caliper gives you the digits.

In the image shown, the 0 on the movable arm is after 27 and checking the 0 to 10 scale on the movable arm aligns with the fixed arm at 7.5. This makes the reading 27.75mm.

Notice there are 20 divisions on the movable arm, which corresponds to the nearest 0.5mm.

Make a few measurements and this will get you over the learning curve. Put paper over the bottom of the screen to help you learn.

• @stainless6SteelRat your answer is wonderful which makes me learn this,i have doubt if the reading is at zero it means i have to move division on small scale to move 1cm on the main scale right? Jul 22 '20 at 14:55

The 0.05mm is the readability of the caliper and thereby, the tolerance of your measurement.
Reading the caliper is the same as any other.