CRT handling Was: Re: It's ALIVE!

From: Dwight Elvey <elvey_at_hal.com>
Date: Wed Feb 24 14:50:11 1999

Christian Fandt <cfandt_at_netsync.net> wrote:
> Upon the date 10:20 AM 2/24/99 -0500, Steve Robertson said something like:
> >
> -- snip --
> >There is a common misconception that the amperage is what kills you. That
> >is simply not true. At low frequency (50-60HZ) and DC, the human body is a
> >simple resistive circuit and will obey OHMS law E=I*R. It is impossible to
> >have one without the other!
> >
> >IIRC a current of approx 100MA through the trunk of the body is enough to
> >stop the heart. If you measure the resistance of your body and plug those
>
> Uhh, that should be 100uA (_micro_ amperes) and even several uA only can
> stop the heart under the correct conditions.
>

Hi
 The number I remember was 20-50mA. There are two ways to kill
one self. One is to cause the heart to convulse and the other
is to burn the tissue. To cause the heart to convulse takes
a smaller amount of current but the heart will usually restart
when removed from the current. This is why high DC is more
dangerous than AC. With DC, your muscles tend to lock, holding
onto the hot wire. This keeps the heart locked up also. With
low frequency AC, it tends to make the muscles jerk. This usually
separates one from the hot wire. In all of these cases, so far,
at most, artificial respiration will bring one back. In the
next realm is the higher currents that actually burn the heart
tissue. You rarely recover from this. Now on to RF. Even though
there may be a high enough current, most only
suffer surface skin damage. This is because of the fact that
the current in RF tends to flow mostly on the surface because
fast change in directions of current also require that the magnetic
field associated with it be able to change as well. Changing
magnetic fields create eddy currents in conductors that limit
the rate that they can penetrate that conductor. This is
called the "Skin Effect". What it means is that for RF or
short pulse DC ( such as lightning ) the current tends to
stay on the surface of your body and not effect the internal
parts as much. This is why some live through lightning strikes
but the guy working on the washing machine is dead.
 While working around CRT's the high voltage anode is a problem.
It will not usually kill one but it will make you uncontrollably
jump. Where your hand and arm go, may be through the back of the
tube. This is usually a bloody experience.
Dwight
Received on Wed Feb 24 1999 - 14:50:11 GMT

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