RE: [CAD_CAM_EDM_DRO] Dynamics research DRO

Thanks Jon

I did open up the one that doesn't work; found a bunch of swarf in it.
Plan to do some "real cleaning" on it but haven't yet. Reason for
questions now is I wanted to start looking for more scales anyway as
would like to have at least 3; just have 2 now.

On the scale (glass I think) itself there's the number 500 stamped
(which I assume means 500 lines per inch; also from the model number).
It has an led plus what appears to be a photo cell. At a glance there
are no other noticeable electronics.

The display has a mfg date of (I think if I recall right) 1976. This
came off an old non-working huge non-working horizontal mill talked to
the scrap buyer at the sale; told him I'd try to buy it and give it to
him if he wouldn't bid against me as I had no way to move it if he'd let
me remove the DRO & mist coolant system and he said OK. Gave $37.50 for
it. Guess I'm lucky anything works! Only controls are on/off and reset
(or zero; don't recall terminology). If you slide the working scale
back & forth the reading just keeps adding.

I'll shoot some pix today; should I send them to you direct or post to a
"section?" As I recall there's been talk of the files, photo or
something on this list filling up.

Only reason I'm on this list is occasionally there's some real
interesting info; most is WAY over my head! :)

Lew


-----Original Message-----
From: elson [mailto:elson] On Behalf Of Jon Elson
Sent: Thursday, August 29, 2002 12:37 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Dynamics research DRO

LEW BEST wrote:

> Hi
>
> I was at an auction a couple of weeks ago and got hold of a Dynamics
> Research model 750 (display) with 2 model LMT 500-19-9-0 scales. The
> display seems to be good (X, Y, Z axis readouts) but only one of the
> scales works.
>
> The scales are linear type encoders, 500 lines per inch. On the back
> they say channel A; black/white, channel B; green/black, +5v; red, and
> com; black. These correspond to the wire colors.
>
> What I was wondering was if I'd need to find other encoders to match
> these or if I could use another type, brand, etc. encoder?

Well, you really need to know a little more about the encoders. Are the
signals analog or digital? In other words, does the readout box
interpolate
the signals to a higher resolution, or just display the base resolution
of the
scale? Second, you need scales that match the resolution accepted by
the readout. This is pretty much standard, nowadays, and is metric.
0.0005" resolution is slightly coarser than 0.01 mm, so you can't get to
all possible values of the 1/2 thousandth resolution. Some readouts
fudge
this by interpolating the flicker in the signals, others just can't get
to
some readings at any position. Others use scales that have higher
resolution
than 0.01 mm. Anyway, you need to find out what resolution these scales
are,
or what res. the readout can accept. (There may be switches inside to
set
each axis for resolution, which direction is +, and a double mode for
lathe
diameter readout.)

Before giving up, you might just open up the dead scale (you can't
really break
it any worse than it is now) and look for crud on the sensors, broken
wires
(in the connector, too), burned out light bulbs, etc. (Really old
scales had
incandescent bulbs in them, but most newer ones have IR LEDs.)

Jon

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