Path: utzoo!mnetor!uunet!husc6!cmcl2!nrl-cmf!ames!eos!aurora!labrea!decwrl!decvax!tektronix!midas!jeffw
From: jeffw@midas.TEK.COM (Jeff Winslow)
Newsgroups: sci.electronics
Subject: Re: shock box
Message-ID: <2697@midas.TEK.COM>
Date: 10 Mar 88 19:51:30 GMT
References: <307@trwind.ind.TRW.COM> <4881@videovax.Tek.COM> <1231@uop.edu> <3616@bloom-beacon.MIT.EDU>
Reply-To: jeffw@midas.UUCP (Jeff Winslow)
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 28

In article <3616@bloom-beacon.MIT.EDU> wolfgang@mgm.mit.edu (Wolfgang Rupprecht) writes:

>Although the box only packed a small charge,
>
>	Joules = 1/2 Capacitance * (Volts ** 2)
>	(* 0.5 0.5e-6 2e3 2e3)
>	1.0 joule
>
>four people (out of tens shocked) asked me days later, if I thought it
>was possible that the box to cause back pain. I thought nothing of it
>at first. Then it dawned on me that each of these four people had
>received jolts from on hand to another. Hmm. That got me worried. 

There may be a good reason for it. In pawing through UL1244, which is the U.L.
standard for safety of test and measurement equipment, I found a definition
of electric shock danger (which the equipment being certified may not have)
which includes the following points of interest: If the voltage between two 
accessible parts is between 450v and 15kv, the product of the capacitance
between the two parts and the voltage may not exceed 45uC. In your case it
was 1mC - over 20 times that! For higher voltages they set a limit of 350mJ
of available energy. 1 joule may be more than you think.

The difference between the threshold of feeling and the threshold of fatality
for current flowing through your body is less than a factor of 20. UL shock
standards are generally set at a somewhat conservative threshold of feeling.
Anyone who messes around with this stuff - please be careful.

						Jeff Winslow