# Source: https://learn.adafruit.com/calipers/digital-vs-dial-calipers.md

# Calipers

## Digital vs. Dial Calipers

There are a few different types of caliper you'll come across: digital, dial and vernier. We're going to skip vernier and show the difference between dial and digital.![](https://cdn-learn.adafruit.com/assets/assets/000/000/847/medium800/hand_tools_pinion.jpg?1396766397)

Dial calipers use a mechanical system consisting of a rack and pinion, there's a gear-set inside as well that moves the dial in increments of one thousandth of an inch (or hundredth of a mm). To read, the 'most significant' value is read from the rule and the fractional value from the dial. The nice thing about dial calipers is that they don't use batteries and although are not waterproof, work well even if damp.

There are some downsides: if they are dropped, the rack and pinion can get out of alignment (especially on cheaper calipers) and it can be difficult to recalibrate. They're a little tougher to read and often are either imperial or metric (but not both).

![](https://cdn-learn.adafruit.com/assets/assets/000/000/848/medium800/hand_tools_nopinion.jpg?1396766406)

Digital calipers don't have any rack/pinion/gear system. This makes them more shock-proof which we like (since we're a little clumsy and have dropped the calipers a few times).

Digital calipers can also easily convert from inches to mm and back which we really like since a lot of electronics is mixed-units.

![](https://cdn-learn.adafruit.com/assets/assets/000/000/849/medium800/hand_tools_oneinch.jpg?1396766409)

![](https://cdn-learn.adafruit.com/assets/assets/000/000/850/medium800/hand_tools_254mm.jpg?1396766416)

So how does a digital caliper work without gears? it turns out that underneath the plastic 'ruler' overlay is an engraved copper design. The slide part has a circuit board with thin strips that look like a 'comb'. The comb and copper pads form a grid of capacitors,[&nbsp;two conductive plates separated by the dielectric plastic overlay.](http://en.wikipedia.org/wiki/Capacitor)&nbsp;As the comb slides over the copper pattern, the capacitance between the plates changes. If the patterns are engraved precisely, even very small changes in capacitance can be detected by an analog interface (such as an RC timer or oscillator).

![](https://cdn-learn.adafruit.com/assets/assets/000/000/851/medium800/hand_tools_capstrip.gif?1447976572)

[Photo from PhysicDude](http://www.flickr.com/photos/50241702@N04/5227386500/ "Link: http://www.flickr.com/photos/50241702@N04/5227386500/")

This means that if the dielectric changes it can mess up the readings. For this reason, digital calipers can give jumpy readings if they are dirty or wet.

- [Previous Page](https://learn.adafruit.com/calipers/overview.md)
- [Next Page](https://learn.adafruit.com/calipers/storage.md)

## Featured Products

### Mitutoyo - Absolute Digimatic Digital Calipers, 6 in.

[Mitutoyo - Absolute Digimatic Digital Calipers, 6 in.](https://www.adafruit.com/product/294)
The most useful tool we've ever laid our hands on. &nbsp;We thought we'd use them just for electronics but then we got our hands on these calipers and had so much fun we started measuring&nbsp;_everything._

They're indestructible - which is good because we don't...

No Longer Stocked
[Buy Now](https://www.adafruit.com/product/294)
[Related Guides to the Product](https://learn.adafruit.com/products/294/guides)
### Premium Digital Stainless Steel Calipers

[Premium Digital Stainless Steel Calipers](https://www.adafruit.com/product/1724)
The most useful tool we've ever laid our hands on. These calipers are really good quality and an excellent choice if you need something better than a cheap 'disposable' pair of digital calipers but you're not quite ready for a set of high-end Mitsutoyo calipers. These digital...

No Longer Stocked
[Buy Now](https://www.adafruit.com/product/1724)
[Related Guides to the Product](https://learn.adafruit.com/products/1724/guides)
### Solar Digital Calipers

[Solar Digital Calipers](https://www.adafruit.com/product/3720)
_Praise the sun!_ You will never have that awkward situation where your caliper battery dies just when you need to take a measurement. Sure, if you have the budget, [we recommend these near-indestructible high-end Mitutoyo...](https://www.adafruit.com/product/294)

In Stock
[Buy Now](https://www.adafruit.com/product/3720)
[Related Guides to the Product](https://learn.adafruit.com/products/3720/guides)
### Messograf Pen Calipers

[Messograf Pen Calipers](https://www.adafruit.com/product/810)
Discontinued - **you can grab [Solar Digital Calipers&nbsp;](https://www.adafruit.com/product/3720)instead!&nbsp;**

&nbsp;

Caliper rule? Tire tread gauge? Ruler? Thread scale? Writing instrument? The Messograf is all of these in one.  
  
It is a...

No Longer Stocked
[Buy Now](https://www.adafruit.com/product/810)
[Related Guides to the Product](https://learn.adafruit.com/products/810/guides)

## Related Guides

- [Secret Hollow Book Intrusion Detector](https://learn.adafruit.com/secret-hollow-book.md)
- [Necomimi Brainwave Cat Ears Teardown](https://learn.adafruit.com/necomimi-brainwave-cat-ears-teardown.md)
- [Ambient Sound Machine](https://learn.adafruit.com/ambient-machine.md)
- [Personal Torch 3000](https://learn.adafruit.com/pt3000-personal-torch.md)
- [Butterfly Bench with Edge Lit Acrylic](https://learn.adafruit.com/butterfly-bench-with-edge-lit-acrylic.md)
- [Bass MIDI Stomp Box](https://learn.adafruit.com/midi-bass-synth-stomp-box.md)
- [Build a Custom Front Panel](https://learn.adafruit.com/build-a-custom-front-panel.md)
- [Collin's Lab: Soldering](https://learn.adafruit.com/collins-lab-soldering.md)
- [3D Printed Custom Keycaps](https://learn.adafruit.com/3dprinted-custom-keycaps.md)
- [Fiddy - the FTDI Clip](https://learn.adafruit.com/fiddy-ftdi-pogo-pin-clip.md)
- [Photo Light Box](https://learn.adafruit.com/photo-light-box.md)
- [DIY On/Off JST Switch Adapter](https://learn.adafruit.com/on-slash-off-switches.md)
- [Making Edge Guards for Hand Tools Using Hand-Moldable Plastic](https://learn.adafruit.com/hand-moldable-edge-guards.md)
- [USB Locket](https://learn.adafruit.com/usb-locket.md)
- [DIY 3D Printing Filament](https://learn.adafruit.com/diy-3d-printing-filament.md)