Re: More questions !!

Hello Jon,

Another way to get high resolution from an encoder is to use them as an analog transducer. If you look at the raw output from
an encoder, linear or rotory, before it goes into a comparator, you will see that it is gradually varying from a minimum to a
maximum and then back to a minimum. If the gratings and electronics are designed properly, the output will resemble an offset
sine wave. That sine wave is feed to an A-D converter that converts it to "higher resolution" digital output.

That is how a lot of high end equipment work. The first step when working on the equipment is to adjust the analog encoders.
Basically, you adjust the gain and zero offset of each encoder before it goes to the A-D. Afterwards, you hook up a scope and
adjust the phasing between the channels. Just like an old fashioned "Lissajous sp? display".

If one think about it, dial calipers and other equipment do the same. If one peel apart one, a very rough grating can be seen,
not enough at all to get 1 mil resolution.

Bertho
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> Jon Elson <jmelson@...> wrote:
>
> -------- > snip
> Well, to get resolution similar to what I've got with my good leadscrew and
> rotary encoders, I'd need a film with 5000 lines/inch, meaning I'd need
> a photoplotter which could put down 10000 pixels/inch, with an accuracy
> of a few percent in the location of each pixel. The big metrology
> companies, Sony, Teledyne-Gurley, Heidenhain, etc. have the very
> exotic optical gear to do these, I sure don't.
> Jon