I got this from one of my other car lists. Interesting.
-Aron Travis-
"always in a automotive frenzy"
Ed Mellinger wrote:
>
> Hi Folks,
>
> I work with 1600 volts on the deck of a ship, so I was motivated to do a
> bit of reading about electrical safety. Here's the gist of what I
> learned. I can provide further references if anyone's interested...
> it's a bit off the EFI topic.
>
> DISCLAIMER: I'm forwarding this to the list as general background
> material on an important subject. It is based on my personal
> interpretation of things I've read in the literature. This material has
> not been reviewed by any safety agency, is not guaranteed to be
> accurate, and must not be used for design or other human safety
> purposes. 'Nuff said.
>
> [Intro stuff deleted]
>
> "Though we speak of hazardous voltages, the real villain is current
> forced through the body, and in particular through the heart, by the
> voltage in question. For a given voltage the current depends on the
> skin resistance, which varies by orders of magnitude depending upon the
> individual and the presence of water or perspiration. The physiological
> effects of current flow also vary, but typical examples are the
> following:
>
> DC AC
> threshold of perception 5 mA 1 mA
> painful shock 30 6
> muscular control lost ("let-go threshold") 50 10
> ventricular fibrillation (3 sec) 500 100."
>
> "Since average skin resistance is between 1,000 and 10,000 ohms, it is
> easy to see that any voltage over 100 V should be regarded as
> potentially lethal, and 1600 V as almost instantly so. According to the
> literature there is very little middle ground in human shock cases:
> there is either a temporary stunning effect and a great story to tell
> later, or the heart stops beating and the victim is found dead."
>
> Obviously your ignition's 25 kV will pretty much have its way in forcing
> current through your body, but fortunately this multi-kV source is both
> current and energy limited, to the extent that I've never heard of
> anyone being electrocuted by their car. BUT there's plenty of current
> for involuntary muscle contraction, and as has been noted, if that
> throws you into the fan or a v-belt, you could easily be hamburger
> anyway.
>
> Hope this is interesting... now go home and make sure the GFIs in your
> garage work!
>
> Ed Mellinger
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