View Full Version : Digital calipers

02-08-2002, 10:31 AM
Does anyone know how digital calipers work? I had mine apart. Underneath the printed scale is a copper-plated board. The copper is etched away in a rectangular pattern that repeats every 0.2 inches. On the slider is another plated copper board with 48 etched rectangles .025 inches wide. Inside the rectangles are tiny holes, maybe .015" diameter. The holes are centered in the rectangles horizontally. Vertically, they are are at different heights, thus: 1, 3, 5, 7, 2, 4, 6, 8. The pattern is repeated 6 times, giving 48 rectangles.

My question is: how does this thing work? What is the principle for the non-contact reading, and how to they get from a sensor geometry of .025" to a precision of .0005"?


02-08-2002, 07:40 PM
Vernier system ?
.025 / 48 = .0005

02-08-2002, 07:51 PM
Howinhell did you get them apart, and did you get them back together?

02-08-2002, 09:47 PM
My question is, why in hell did you take it apart!!???

This sounds like a Gray code encoder, it allows the electronics to determine if it is increasing or decreasing (such as a shaft's position and velocity). The beam of the caliper will be encoded with miniature bar magnets.

02-11-2002, 11:22 PM
<font face="Verdana, Arial" size="2">Originally posted by JCHannum:
Howinhell did you get them apart, and did you get them back together?</font>

Just take out all the tiny screws, then reverse the process. Mine works smoother now because I cleaned it while it was apart.

02-12-2002, 06:16 PM
"You the man"

I have a habit of disassembling everything I own, usually right after I acquire it.

Wife can't stand it.

Just gotta know what makes it tic - probably why I was never left alone with our newborn!

02-12-2002, 07:18 PM
The Mitutoyo that I am familiar with don't have any screws. Never could figure how the rascals got them together.

02-13-2002, 01:34 AM
They either snap together or have screws hiding under labels to prevent "Consumer Modifcation".

Intel used to make the 486 chips so if you plugged it in the "bad" way it would split in half to prevent warranty claims from goofs playing with static sensitive parts. I found these out when a technician I know did this in error, I called Intel to try and get the $600 chip replaced - first thing they asked is "did it break in half? Yes? No warranty, it is a feature to protect our interests blah, blah, blah&gt;"

I think you should leave your good calipers alone and tear apart a $10 Chinese copy instead...