[Jukebox-list] Grounding Issue

[Jens Hultgren]

That sounds reasonable. You have to separate the hazards from electric shock
- heart fibrillation is one, severe burns another. We once had a patient, a
young man who had climbed a train and had 10000 volts run through his body.
He was unconscius, but appeared almost normal at first inspection. Looking
closer, he had en entrance wound in his arm and an exit through one foot.
The current had passed through the bone marrow, charring his bone. He could
not be saved.

I have to rethink what I wrote, the real hazard with mains voltage frequency
is heart fibrillation.

>From Wikipedia

Issues affecting lethality

"Other issues affecting lethality are frequency, which is an issue in
causing cardiac arrest or muscular spasms, and pathway - if the current
passes through the chest or head there is an increased chance of death. From
a mains circuit the damage is more likely to be internal, leading to cardiac
arrest.

The comparison between the dangers of alternating current and direct current
has been a subject of debate ever since the War of Currents in the 1880s. DC
tends to cause continuous muscular contractions that make the victim hold on
to a live conductor, thereby increasing the risk of deep tissue burns. On
the other hand, mains-frequency AC tends to interfere more with the heart's
electrical pacemaker, leading to an increased risk of fibrillation. AC at
higher frequencies holds a different mixture of hazards, such as RF burns
and the possibility of tissue damage with no immediate sensation of pain.
Generally, higher frequency AC current tends to run along the skin rather
than penetrating and touching vital organs such as the heart. While there
will be severe burn damage at higher voltages, it is normally not fatal.

It is believed that human lethality is most common with AC current at
100-250 volts, as lower voltages can fail to overcome body resistance while
with higher voltages the victim's muscular contractions are often severe
enough to cause them to recoil (although there will be considerable burn
damage). However, death has occurred from supplies as low as 32 volts."

  Jens

On 5/6/06, Crispin Murray <crispin at guilde.co.uk> wrote:
>
>
> Following on from what Wes has said, 50 v is sufficient potential to
> enable
> enough current to flow to stop the heart (in fact people 40 v is just
> about
> enough).
> However do bear in mind the internal resistance of batteries etc. which
> will
> cause the voltage to drop (and therefore the ability of current to flow),
> or
> other limitations within a power supply if you want to try this out at
> home!
> (Actually please don't try this at home).
> When I used to work for for a major broadcasting organisation we used to
> have a separate 50 v DC supply (with battery backup - lots of them!) to
> hold
> all the relays for switching studios, networks, feeds etc., so they were
> immune to any minor disturbance in the mains supply. As Engineers we were
> all made extremely aware that with virtually no resistance (or current
> limiting) within this supply, it had the potential (!) to prove fatal.
>
> Crispin
>
>
>
> From: Jens Hultgren <drjukebox at gmail.com>
> Reply-To: Jukebox mailing list <jukebox-list at lists.netlojix.com>
> Date: Sat, 6 May 2006 14:07:24 +0200
> To: Jukebox mailing list <jukebox-list at lists.netlojix.com>
> Subject: Re: [Jukebox-list] Grounding Issue
>
> Just curious - how would I die from 50V DC?
>
>      ;o) Jens
>
> On 5/6/06, Crispin Murray <crispin at guilde.co.uk> wrote:
> >
> >
> > I think you¹ll find it was Tesla who came up with 60 Hz 117 v, whilst
> > Edison
> > was  still persevering with 50 v DC - which unfortunately doesn't go
> very
> > far, is lossy in cables, awkward to generate and distribute. This is why
> > Tesla and Edison fell out, and why (I believe) Tesla's Power Station at
> > Niagra Falls is still there and Edison's isn't.
> > 50 v DC is also just enough to kill you, which is unfortunate because I
> > think that was one of Edison main reason's for it.
> > I'm NOT having a knock at Edison btw (I know he is a US national hero),
> > after all it was him who started the whole record business off in the
> > first
> > place, and where would we all be without that!
> >
> > Crispin Murray
> >
> >
> >
> > From: Ron Rich <ronnnrich at yahoo.com>
> > Reply-To: Jukebox mailing list <jukebox-list at lists.netlojix.com>
> > Date: Fri, 5 May 2006 17:44:33 -0700 (PDT)
> > To: Jukebox mailing list <jukebox-list at lists.netlojix.com>
> > Subject: Re: [Jukebox-list] Grounding Issue
> >
> > Don't know if this is true--was once told that 60 Hz was chosen because
> at
> > anything less, humans can see it in an incandesent light (I know I can
> > sense
> > it anytime I'm somewhere that uses 50 Hz). What I was told  was that
> > Westinghouse, who "invented" (while one of Edsion's "tinker-ers")
> the  60
> > Hz
> > AC that we use today,   hated the "flicker" of less than 60Hz.
> >   Ron Rich
> >
> >
> >
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> > Jukebox-list at lists.netlojix.com
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