Hi Gregg:
> There was also a very good (but short) article by Tektronix in the 70's
> called The Lethal Current.
>
> It concluded that currents between 100 mA and 3 Amps were more lethal that
> currents of more than 3 Amps because those high currents tended to 'restart'
> the heart.
Hmm. Having been the manager of product safety at Tektronix in
the '70's, I don't recall such an article. At least not by that
name.
Electric energy causes various injuries to the body depending
on the magnitude of the energy. Only two of the injuries can
lead to a fatality.
The two injuries are fibrillation of the heart, and overheating
of internal organs, especially the liver.
Fibrillation is caused by ac current in the range of 50 mA to
500 mA (external connections) where the current pathway through
the body includes the chest (and the heart). Above 500 mA,
fibrillation is not a likely consequence. (And, I believe I
am correct in asserting that dc cannot cause fibrillation.)
Overheating of internal organs is a function of power dissipated
in the body, where the body impedance can be taken as 1000 ohms.
The power required depends on the time of contact. Electric
utility linemen are subject to such injury. Consider 1 ampere
through 1000 ohms is 1000 watts! (The electric chair kills by
over-heating the internal organs, not by fibrillation.)
So, Gregg's statement that there is both a lower and upper limit
for fibrillation is correct (although I do not agree with Gregg's
values).
Best regards,
Rich
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