Re: [CAD_CAM_EDM_DRO] Linear Encoders

Eric Keller wrote:

> The first was the one that said the HP is a chip with a grid
> incorporated in its layout. If this is true, then do they have the
> layout we need for 500 lines per inch? i would guess that they are not
> willing to give up on the glass scale market. Anyone ever break apart
> an Accurite?

I took apart a couple of Teledyne/Gurley linear scales. They were of
low resolution, and in
bad condition, with scrapes on the grating, so I didn't devote a lot of
time to trying to repair
them. But, both the scale and grating were made from glass.

> The rotary encoders have a metal grid, i seen it.
> if HP or someone else makes a detector that don't need a grid,that is
> great, and i think we know what to do. The other point is that if HP
> doesn't make the right chip that isn't stopping us from using the
> rotary encoder scheme.

>
> Otherwise, I'd like to volunteer whoever it was that emailed UsDigital
> to ask them if they would print us some 500 line per inch and sell it
> without a head available, and we could use some of that in the head.
>
> Finally, It seems that you could use the two head outa phase scheme to
> double the resolution of a grid as proposed in the other message i
> deleted. My thought is that the spacing would have to be correct, but
> that you could use ttl logic to convert the two signals into one.
>
> Finally, i must say i am not totally committed to the "lime jello"
> approach to linear encoders, because my (currently imaginary) budget
> probably would include store bought encoders. However i am an
> engineer that can't say no to a project.
> eric

Yes, if you can get the grating at the desired resolution, a piece of
that grating can be tilted with
respect to the scale, and it will show moving bands of light and dark,
by the Moire' principle.
If you adjust the tilt angle correctly, it will provide bands spaced
correctly to drive detectors
in quadrature.

Jon