Re: [CAD_CAM_EDM_DRO] Re: Creating long straight edges

cnc_4_me wrote:

>
> The part i remeber that was interesting was how he measured the
> height of the ways for the lenght of the machine. He said the very
> ends of the machine bed were usally in pretty good condition. So he
> would put a couple of presion blocks on each end and stretched a
> piece of piano wire over the blocks. On both ends of the wire he
> placed 20 to 40 pound weights to stretch the wire tight. He then had
> a precision electronic guage that would measure the distance from the
> wire to the bed....
>
> I have pondered a few times over the years how this system could work
> and i have not thought of a working system i could make. Maybe the
> blocks on each end were nonconductive and he used a precision block
> and a feeler gauge to check for continuity. But he implied he used a

> electronic insturment....

This most likely is a capacitive sensor. A plastic block that rides on the ways
and comes very close to the wire, with a strip of PC board material on the
top could be the sensor. An oscillator circuit could be built into the block,
with the capacitor of the oscillator made between the wire and the PC board's
copper. The frequency could be read out by a meter. I think I could actually
build something like this from just about this much information.

Jon