[Shop-talk] Micrometers

[Mark Andy]

Howdy,

On Thu, 29 Oct 2009, David Scheidt wrote:
> Yes.  No moving parts.  There's a printed pattern on two printed circuit 
> boards.  A sensor detects the change of capacitance as the two parts 
> move relative to each other.  With standard PCB fabrication methods, you 
> can get something like a tenth (one 10,000th of an inch) accuracy in 6" 
> board.  Some apparently use induction, but the idea is the same.  The 
> circuit involved is about a second semester project these days.  Only 
> precision machining the caliper needs is to make sure it runs square. 
> A cheap digital caliper (assuming it's not bent or something) is more 
> accurate than an expensive non-digital one.  Progress is cool, 
> sometimes.

That's cool to hear.  Thanks!

I will say there's one advantage to a dial caliper... If you're like me 
and it might sit six months before you grab it to measure something, its 
unlikely to have a dead battery.

:-)

Mark