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From: vince@tc.fluke.COM (Craig Johnson)
Newsgroups: sci.electronics
Subject: Re: Electric Fences (safety)
Summary: Watch out!
Message-ID: <13569@fluke.COM>
Date: 2 Jan 90 21:22:19 GMT
References: <5593@shamu.WV.TEK.COM> <12346@cbnewse.ATT.COM> <25525@cup.portal.com>
Sender: news@tc.fluke.COM
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Organization: John Fluke Mfg. Co., Inc., Everett, WA
Lines: 41

A couple of years ago I went out and bought the cheapest "fence charger" I
could find (to keep the dog out of the garden) and when I got it home and
checked it out I found that it consisted of NOTHING MORE THAN AN AC LINE
CORD AND  TRANSFORMER mounted in a plastic box.  There was no fuse, no
interrupter, and nothing to limit current other than the physical
properties of the transformer.  Guess what? it WAS NOT UL approved!

Needless to say, I was concerned about the safety of this thing, so I
decided to see just how much of a shock it could produce and whether a
person could safely handle it.  Not wanting to risk my life checking this
out, I devised to unground myself, connect one electrode to my wedding
ring, and use a second electrode to tap the back of the same finger.  This
was done, of course, to limit the current path to a single finger and keep
it as far as possible from more critical body areas.  I don't remember at
the moment how the second electrode was situated, but I'm sure I didn't
hold it in my other hand!  Then using a resistor substitution box, and
starting at a very high value, I varied the input to the transformer,
shocking my finger, until I reached a point where I decided it was unsafe
to proceed further.  I don't remember the voltages measured, but I recall
stopping at 1/3 to 1/2 of the way to full zap.

The "charger" was returned to the dealer the next day.  Eventually, I
constructed my own fence zapper based on pulsing an automotive ignition
coil, which was much safer.  The zapper I ended up with only caused mild
discomfort to people, but was very effective on a dog's wet nose and he was
quickly convinced to stay out of the garden.

The moral:  Don't assume all electric fences are safe to grab!  You may
be betting your life if you are wrong!

	WARNING - I do not advise anyone to test "fence chargers" by
		  shocking themselves.  This practice could result in
		  your death!  (No smilely on this one).

	DISCLAIMER - Nothing expressed in this posting is intended to
		  represent the views or advice of the John Fluke Mfg. Co.

------
	Craig V. Johnson		...!fluke!vince
	John Fluke Mfg. Co.
	Everett, WA