Don Foreman wrote:

I wish I could figure out how those Chinese calipers get .0005"
resolution.

The resolution is even higher. It is 1" / 20480. Theoretical. I get a
few 1/1000mm out of them with overshampling and averaging.


I took one apart. The features on the capacitive scale
and reader are not nearly that small: the reader's strips are on
.025" centers and the scale's features are .100" wide with spaces
between them that look like they were routed with an .0125" dia (might
be 0.5 mm dia) endmill.

Have you seen what I have added to my HP in the meantime? I didn't
describe how the electronics work*). But I have put a lot of material
how the signals look like and about the mechanical arrangement of the
couppling and shielding caps.

See: http://www.motor-manufaktur.de/werkstatt/09_yadro/part_1.html


*)
Because I don't know. I have only a vague picture of it: It works with
the vernier principle and it seems that it does enhance resolution by
messuring the coupled voltage. I _guess_.
Still have to laugh when I get remembered how much fun it was to use the
HP-54645D Mixed signal scope. :-) Geee, and they sayed that I can keep
it as long as I want. What a gem!


BTW:
Hopefully at the end of this month, kits for my digital scales interface
will be available.


Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige