How do digital calipers work?

[Alex Franke]

I noticed in the latest Sears tool catalog that the $100+ digital caliper had the same electronics as the ~$10 one I picked up on Amazon -- must be a part (or I guess maybe the same manufacturer).

That got me wondering how they actually work... same concept as an optical mouse? If so the resolution is pretty impressive... Anyone know for sure?

[Tom Slick]

in a nutshell a sensor picks up a digital scale that is on the flat part of the frame of the caliper.
more detail
http://www.biotele.com/digital_caliper.htm

[LCHIEN]

uh, really well?

OK, tom pointed you in the right direction. Optical printing techniques used for integrated circuits and printed circuit boards has made printing the fine patterns cheap and easy, the fine patterns are used to capacitvely couple and uncouple every time one pattern cell is passed over, by counting them (the signal changes for each cell passing) you can tell which way and how many have passed. The patterns are very accurate and repeatable and stable, giving the calipers their accuracy; the patterns are 6" long on the fixed bar of the caolpers, the moving head has a smaller set but with the same pitch plus the detecting and counting circuit.

[Alex Franke]

Wow.. thanks guys. That's pretty cool. Now I don't have to take mine apart