Calipers
Created by Ladyada
Guide Contents
Guide Contents
Overview
Digital vs. Dial Calipers
Storage
Battery Life & Replacement
Setting the Origin
Basic Measurements
Outer Measurement
Inner Measurement
Depth Measurement
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3
4
7
8
9
10
10
10
11
Step & Relative Measurements
Other Measuring Tips
Measuring Connector Pitch
Measuring Pin-to-Pin Distance
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© Adafruit Industries
http://learn.adafruit.com/calipers
Page 2 of 16
Overview
This tutorial is for the Mitutoyo digital calipers we carry in the Adafruit shop (http://adafru.it/aIH).
They're the best calipers one can get and we're pleased to offer them. We've put together a
basic usage guide here to help people get started.
© Adafruit Industries
http://learn.adafruit.com/calipers
Page 3 of 16
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.
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).
© Adafruit Industries
http://learn.adafruit.com/calipers
Page 4 of 16
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.
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,
two conductive plates
separated by the dielectric plastic overlay. (http://adafru.it/aJ6)
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).
© Adafruit Industries
http://learn.adafruit.com/calipers
Page 5 of 16
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