Re: Re: PIC DRO _now_ i've made it a stupid question
Posted by
Elliot Burke
on 2000-04-06 22:07:06 UTC
Let me shed some infrared on this:
The HP encoders do not use a separate grating in the encoder head. Rather,
they have a single chip which includes very narrow interdigitated detectors.
The pitch of the detector is the pitch of the grating. It cannot be changed
without changing silicon.
Why do they make it hard to hack? Because it makes a better, cheaper
encoder. Less tilt sensitivity, less collimation sensitivity smaller part
count.
Elliot Burke
Date: Thu, 06 Apr 2000 16:41:53 -0500
From: Jon Elson <jmelson@...>
Subject: Re: PIC DRO _now_ i've made it a stupid question
Eric Keller wrote:
HP encoder, and
just use the finer grating, or make an entire assembly and PC board.
You put the
'analyzer' grating on a slant with respect to the long one, and adjust
it until you get the
right quadrature relationship on the two signals. Without exotic
collimating optics, the
higher the frequency of the grating, the closer the gratings have to be
to each other.
Jon
The HP encoders do not use a separate grating in the encoder head. Rather,
they have a single chip which includes very narrow interdigitated detectors.
The pitch of the detector is the pitch of the grating. It cannot be changed
without changing silicon.
Why do they make it hard to hack? Because it makes a better, cheaper
encoder. Less tilt sensitivity, less collimation sensitivity smaller part
count.
Elliot Burke
Date: Thu, 06 Apr 2000 16:41:53 -0500
From: Jon Elson <jmelson@...>
Subject: Re: PIC DRO _now_ i've made it a stupid question
Eric Keller wrote:
> Jon wrote:Yes, precisely! You could either take the sensors and logic out of an
> Really, if someone can come up with accurate grating patterns on film
> or
> glass, it is fairly easy to make your own linear encoder. Does anyone
> have
> any ideas on
> where to get such grating patterns?
>
> Jon
>
> It seems that they can print the strips, so the question is will they
> do it?
> the Heds module i'm looking at is a rotary, so it has two sets of
> grates to
> look at
> It has a small stainless steel grating with ~6 holes apiece,
> apparently
> photoetched.
> The thought i'm having is what is stopping you from using a piece of
> the
> linear strip as your grating. might need a larger pair of holes to
> keep the
> light in the right place.
HP encoder, and
just use the finer grating, or make an entire assembly and PC board.
You put the
'analyzer' grating on a slant with respect to the long one, and adjust
it until you get the
right quadrature relationship on the two signals. Without exotic
collimating optics, the
higher the frequency of the grating, the closer the gratings have to be
to each other.
Jon