[Shop-talk] Digital Calibers

[Chris Kantarjiev]

> There's a  printed pattern on the PCB in the sliding bit, and another,
> inside the fixed part.  As you move them, the capacitance changes.  It
> goes  up, reaches a peak, and then falls, and the goes up, etc.

Exactly right. Some of them have relative encoders, but some have
absolute encoding, too... and some are using inductance rather than
capacitance.

http://www.mitutoyo.co.jp/eng/products/sokuchouunit/Scale.pdf

has a bunch of interesting info.