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From: mahaun@sactoh0.SAC.CA.US (Mark A. Haun)
Newsgroups: sci.electronics,sci.misc
Subject: Re: Where can I buy an inexpensive strip chart recorder?
Summary: try ham swaps
Message-ID: <3972@sactoh0.SAC.CA.US>
Date: 15 Sep 90 00:59:26 GMT
References: <1990Sep12.162833.15567@wrl.dec.com>
Organization: Sacramento Public Access, Ca. USA
Lines: 59

In article <1990Sep12.162833.15567@wrl.dec.com>, reid@wrl.dec.com (Brian Reid) writes:
> 
> I want to buy a "strip chart recorder". I thougrht this was a very well-known
> device, but I just got back from my local electronics store (Fry's) and the
> staff there didn't even know what one was. So maybe I need to remind you that
> a strip chart recorder is a box that has an analog input, a roll of paper, a
> clock motor to drive the paper, and a pen. The pen wiggles up and down
> according to the signal applied to the analog input.
> 
> Does anybody have any suggestions for stores in Northern California or else
> mail order places that might sell me such a device?

I picked up mine at a local amateur radio swap meet.  I think that
digital recording is common enough now that most of the
old-fashioned motorized units are not being sold new.  My unit was
made by the Esterline Angus company *many* years ago, but the paper
drive system still works well.  It uses color-coded gears which you
can switch around to get 10 different drive speeds (5 "slow", 5
"fast").  And all of that for just $20.

Unfortunately, I can't find a source of chart recorder ink for it
:-( !  The ink/pen system basically consists of:

1) A long, narrow, rectangular tray which is to be filled with the
   right sort of ink, and a cover which snaps onto the tray.

2) A siphon tube which is lowered into the tray, and is connected
   to a very flexible rubber tube which leads to the pen mechanism.

3) A long, thin, metal pen arm, which has a tiny capillary tube
   inside for the ink to flow through.

4) An incredibly tricky pen balancing system to get the thing to
   slide smoothly across the paper (the arm is powered by the
   current being measured [+/- .5 ma]; there doesn't appear to be
   any sort of active-pen-drive system).

The problem with normal ink is that it will evaporate from the pen
tip whenever the machine isn't recording.  As soon as the ink is
absent from the tip, no more can be drawn out of the ink tray.  The
only way I know of to get the ink flowing again is to hook up a
syringe to the pen tip through a small tube, try to get a good
seal, then pull the syringe handle in a fast motion to pull ink
through the system.

The correct type of ink (I have a small sample, no more :-( )
doesn't seem to evaporate from the tip unless the machine is left
turned off for a relatively long time (several days).  Does anyone
know where this ink can be obtained in small quantities?
Esterline-Angus has a $100 minimum order :-(

> Brian Reid
> reid@decwrl.dec.com

-- 
Mark A. Haun / 3445 Del Mesa Ct. / Sacramento, CA 95821 / Phone: (916) 488-2965
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