Re: [CAD_CAM_EDM_DRO] Re: Fresh run at homebrew DRO

J. Mark Wolf and Doug,

Doug is correct about the output of the scales. The "horizontal quill kits" outputs a analog signal. When they say that the scales are "Digital", they mean that the scale has a LED that show digits you can read, not a digital output. The output can be plugged into a digital readout display but it is configured to accept and decipher the signal. The best place to find out about these system is from the guys that invented these scales at www.proscale.com. ( No Mitutoyo did not invent them) They have digital readouts that should interface with you scale and I understand that the pricing is very reasonable.

As for these digital (analog signal) scales ever having a quadrature output, I have talked to the engineers and they say due to the way the unit is designed, it is impossible to make this happen. Sorry Doug.

Regards,

Dr.D

BTW: Someone asked what I am a doctor of? Well the D is of "D"igital Readout.
I have been servicing all types of dro's for over 15 years.

----- Original Message -----
From: Doug Fortune
To: CAD_CAM_EDM_DRO@yahoogroups.com
Sent: Saturday, January 12, 2002 7:31 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Fresh run at homebrew DRO


"J. Mark Wolf" wrote:
>
> OK. I bought the digital scales from http://www.calaerosupply.com
> They call them "horizontal quill kits".

A warning: a measuring device with "SPC output" is not the same
as a "digital scale" in the DRO sense. Proper DRO scales have
continuous TTL quadrature output of two signals A & B
(or four signals A,/A,B,/B in the case of differential output)
capable of signal speeds in the hundreds of kiloHertz or even
low MegaHertz range.

Such a rapid output enables suitable electronics (ie quadrature
decoder chips) to track the position and velocity with great
resolution.

SPC output devices usually have a fixed length bit stream output,
capable of emitting only one or two positional reports per second.
This is fine for humans reading an LED output, useless for dynamic
CNC position feedback.

Although I don't know about your devices specifically, I would
think the Mitutoyo has quadrature A&B outputs (not clock & direction),
but I'm just guessing.

The "horizontal quill kits" are probably SPC output (ie a binary
stream of encoded digits), and thus the two are incompatable, and
the Calaero scale useless for quadrature feedback for closed loop
control.

If anyone started making long digital calipers with quadrature output
instead of SPC output, we cnc'ers should throw a party.

(The unstated assumption is that you are trying to use DRO output
for dynamic position feedback, not just 'Digital Read Out' of your
last position when the movement has stopped).

Doug Fortune
http://www.cncKITS.com

Addresses:
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