What is a Vernier scale?

The idea behind a Vernier scale is that using two different scales on a measuring device, you can improve your resolution.

For example, standard calipers might have a single scale – you place the object you’re measuring between two reference plates; the scale is attached to one of them and a pointer to the other, and you read off the measurement.

That’s very nice – but the Vernier scale improves on it in a really clever way.

Attached to the pointer of a Vernier scale is a second pointer, whose gradations are in a different proportion to the first – for example, the first scale might have ten marks per centimetre, and the second nine. You then determine, by eye, which of the second-scale marks most closely aligns with any first-scale mark; this would give you an extra decimal place of accuracy.

Why is it interesting?

This is very exciting for me. You know how sometimes you lose an idea? You read about something, then you forget which document it was in and you can never find it again? Well, this is an idea I lost some time around 2006. I’m not certain it’s the same idea, but it has a very definitely similar flavour. This DOME project has been running for something like four years now, and this post alone completely justifies it.

I’m now wondering if something like this can be used with a slide rule.

Who was Pierre Vernier?

Pierre Vernier was born on August 19th 1580 in Ornans in what was then the Spanish Hapsburgs, but is now eastern France, near the Swiss border. He died in the same place in September 1637.