# Graphical Construction Glossary >> Tools. >> Hand Tools >> Digital Caliper

Digital Caliper
An engineer's calliper with a digital readout.
Vernier
A device consisting of a primary scale and a sliding scale, normally the sliding scale has one less divisions than the other. Thereby making it possible to read the primary scale to greater accuracy.
Vernier Calliper
An engineer's calliper with a vernier scale for accurate measurements. Also known as a Vernier Gauge
Dial Calliper
An engineer's calliper with a dial readout. Also know as a Dial Gauge

 A manual read vernier caliper Photo thanks to Wikimedia Commons, User: Lgreen

The instrument above is a standard vernier gauge or caliper that has hardly changed in over a hundred years.

The Vernier is named after it's French inventor Paul Vernier. (1580-1767). It relies on the fact that the eye can only do very vague estimates of how far between two marks on a scale a pointer is, but when two scales are lined up and one of them has say 9 divisions and the other has 10 then the eye can clearly see the point where two of the marks are closest to touching and so get a far greater degree of accuracy.

I had a vernier gauge for years and I am by no means an engineer or did engineering work. It was just so useful for measuring bolts or other round objects. While the extreme accuracy I didn't need just the fact of getting to the nearest millimetre in many case was just too hard to do without it.

Often when taking a sample bolt into a store the guy behind the counter would reach for a vernier gauge to get it right. Many times I have seen them using cheap plastic ones that still do a great job.

 The parts of a vernier gauge Photo and list below thanks to Wikimedia Commons, User: Joaquim Alves Gaspar

1 - Outside jaws: used to take external measures of objects
2 - Inside jaws: used to take internal measures of objects
3 - Depth probe: used to measure the depth of objects
4 - Main scale (cm)
5 - Main scale (inch)
6 - Vernier (cm)
7 - Vernier (inch)
8 - Retainer: used to block movable part

The main points to be gained from this sketch is the fact that there are three possible measurements that can be made with all of these instruments.
1 - The outside size of an object
2 - the internal size of a hole or gap between surfaces
3 - the depth of a hole or the difference between two adjacent faces.
All read from the same section of the gauge.

 A dial calliper Photo thanks to Wikimedia Commons, User: Splarka

The Dial Gauge is an improvement on the simple vernier gauge enabling professionals to make fast and east readings every time.

 A digital caliper Photo thanks to Wikimedia Commons, User: Xofc

Once again an instrument that is easier to use and gives a greater degree of accuracy that other methods. Provided it is kept in good working order.

The digital caliper above measures from .001" to 6" or .01mm to 150mm. It calibrates to zero, and can change from mm to inches with the touch of a button

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"When we build, let us think that we build for ever."John Ruskin 1819-1900

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