re:re: DRO stuff

>Message: 11
> Date: Mon, 13 Mar 2000 07:47:25 +0100
> From: Par Willen <pwillen@...>
>Subject: Re: DRO stuff
>

>Elliot Burke wrote...

>> The HEDS-9XXX encoder optics are set up for a specific grating pitch, so
>> using them with a higher pitch won't work. They contain multiple very
>> narrow detectors connected to each amplifier. With a different pitch

they

>> won't all be in phase, hence lower output. There is some chance that a

360

>> x 3 = 1080 lines/inch there might be some output, maybe not enough to

work

>> the electronics.

>First: This list and r.c.m is literallly a gold mine in time and money
>saving for us newbies, thanks to all ye contributors.

I second that.

>OK, moving on: Is there any technical reason why you use the "3" as a
>multiplier in your example above? I would be very happy indeed to get a
>resolution of 360 x 2 if the quadrature works with that. And if so, has
>anybody seen any 720 lpi strips? : )

The strip frequency matches the readout frequency. If a strip of twice the
readout frequency is used, there will be one open and one closed area over
each detector, giving exactly the same output for any position of the strip!
This is exactly the wrong thing to do, there will be no sensitivity at all
to strip motion.
Whereas with a 3x frequency there will be some reduced output, perhaps
enough to make it all the way through and analog and digital electronics.
I'd want to check this pretty carefully before having much confidence in it.

A linotronic printer could make some strip at 1080 line/inch pretty easily.

Elliot Burke

>Regards
>PiPPi