Re: interface board

On Sat, 8 May 1999 20:10:15 -0500, "Steve Lindsay"
<slindsay@...> wrote:

>If US Digital has encoders to read from a linear strip this
>would cure the problem of slippage.

Well, they DO, but doggonit they (or you should really read "HP") don't
have a linear resolution that in quadrature comes out to some nice
English (or even Metric) quantum.

I even had a chat with one HP 'marketing droid' type about this, and
couldn't seem to get across to him the value of a 250 (X 4 = 1000 in
quadrature) cpi sensor. Since they make a 200 and a 360 cpi model
presently, there's no reason they couldn't build a 250! And NO,
unhappily, their engineering guy told me (hope springs eternal) you
couldn't USE a 250 cpi optical strip with a 200 cpi sensor to get 0.001"
native resolution. The sensor arrays are specific to almost exactly the
optical resolution, so they need to MAKE the bloody thing!! 8(

Their rotaries, however, have lovely and suitable resolutions, so I
guess if you're using zero-backlash ball-screws, and just wanna count
rotational steps to determine position, it's a simple slam-dunk
done-deal already.

I trust most everyone realizes that pretty much all US Digital does is
make the mylar discs/strips that are compatible with the HP sensors (as
well as a line of 'encoder' interfaces for these sensors, to be fair
about it), and then resell the HP sensors? HP has a VERY nice
book/catalog on these "HEDS" sensors of theirs, and I find it much
better a reference than the US Digital "re-makes" of HP's data sheets.
HP's book also shows that building the 'encoder' interfaces is merely a
matter of collecting a few off-the-shelf parts, just incase you're
interested. B)

[not to diminish USD's contribution with the optics ; just that them
'shielding' their clients from HP leaves me a tad cold]

Gar