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Re: Flamed and need reassurance #14058 09/15/02 07:58 PM
Joined: Oct 2000
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sparky Offline
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hey, i found the 'lightning dude' here.....

here's his site


looks like Zeus!

[This message has been edited by sparky (edited 09-15-2002).]

Work Gear for Electricians and the Trades
Re: Flamed and need reassurance #14059 09/15/02 08:50 PM
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motor-T Offline
Member
Well heres my nickels worth.
Generally the human body has between 800-1000 ohms resistance as typical. Body internal resistance, contact resistance, moisture,duration of voltage, as well as the path of the current, we always tell our apprentices 'Right hand right.
According to our little handy chart: 16ma shock is painful just about to the point where you cant let go called" threshold" You may be thrown clear.
23ma shock painful severe cant let go- muscels immobilize- breathing stops
1000ma ventiricular fibrillation(usually fatal)length of time.....0.03 seconds
at 100ma 3.0 second duration.
Generally voltages of less than 40 volts to ground are considered safe. Voltages 50 volts and greater is considered lethal.
And we are required to ground for voltages higher than 50 volts according to 250.20(B)

a 9ma shock is Painful-but can still let go.

Seems to be some misinformation out there.
Mark

Re: Flamed and need reassurance #14060 09/15/02 11:24 PM
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Sean WB Offline
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500 ohms for each appendage, i.e 500 ohms X2 legs, + 500 ohmsX2 arms, + 1000 ohms torso= 3000 ohms .This is what the medical society holds for human electrical resistance for defibrulating equipment etc etc.AJM


I did not get as think so badly as you shocked I did.
Re: Flamed and need reassurance #14061 09/15/02 11:31 PM
Joined: Nov 2000
Posts: 2,236
sparky66wv Offline OP
Member
Even contact area plays a part in the numbers here... Temperature, humidity, the phases of the moon (just kidding [Linked Image])

I guess one would have to meg themselves with 1 cm square copper plates as the electrodes, with a hygrometer, a thermometer, a barometer ? (does a vacuum make a difference?), an effective way to measure humidity of the skin, and at varying voltages to get any kind of usable data.

Heck, the iron, zinc, aluminum, magnesium, copper, and mineral content of your blood would cause nearly an infinite number of variables to contend with...

Any volunteers?

Steve, very cool pic! I'm going to go browse his site now...

[Linked Image]

[This message has been edited by sparky66wv (edited 09-16-2002).]


-Virgil
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Re: Flamed and need reassurance #14062 09/16/02 03:08 PM
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pauluk Offline
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I've always been led to believe that it is the outer layers of skin which provide the greatest amount of resistance. Once below that, either by contact with an open wound or by the application of a high voltage which burns and breaks down the skin's resistance, the resistance of the internal body tissues is quite low.

Contact area, wetness of skin, etc. all play a major part. At the extreme, I can lightly touch one finger of each hand to the probes of a low-voltage 0ohmmeter and get a reading of several megohms. At the other extreme are the figures posted elsewhere from judicial executions which indicate a head to ankle resistance of as little as 133 ohms in one case.

Re: Flamed and need reassurance #14063 09/16/02 04:28 PM
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sparky Offline
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Paul,
that can probably be backed up with mortality & morbidity reports re; path(s) of least R = vasculature compromised....
( thus amputation)
[Linked Image]

Re: Flamed and need reassurance #14064 09/16/02 04:47 PM
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motor-T Offline
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Quote
Dry Conditions: Current = Volts/Ohms = 120/100,000 = 1mA
a barely perceptible level of current

Wet conditions: Current = Volts/Ohms = 120/1,000 = 120mA
sufficient current to cause ventricular fibrillation


This is from one of Joe's suggested links.
Body resistance is going to vary according to conditions.
So we have under dry conditions 100,000 ohms down to 1000 ohms thats quite a variation.
As far as difibrillation they rule is to start out at 200 Joules and work up, a child of course they start at 50.
As I said seems to be some misinformation out there.
Mark

Re: Flamed and need reassurance #14065 09/18/02 06:40 AM
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sparky Offline
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Quote
Body resistance is going to vary according to conditions.

thus the biphasic model defibs....i wonder if there are biphasic electric chairs too??

Re: Flamed and need reassurance #14066 09/18/02 07:44 AM
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Posts: 280
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motor-T Offline
Member
According to my source, during a code, the De-fib machine is in Joules, and the first shock is started at 200, then progressively moved up to 360, if the Pt is still in fibrillation they start again only this time it is started the second time at 360.
For this procedure Body resistance is of no concern, but stopping the fibrillation is whether it be Atrium or ventricular. They grease the paddles with a conductive lubricant and one goes on the left side and to the center of the chest, it is not like a Hand to foot electricution. Didnt someone say that for Legal electrocutions the body resistance is down to about 130 ohms at 25000 volts, .......Talk about overkill huh ? That ought to do it and then some.

Mark

Re: Flamed and need reassurance #14067 09/18/02 02:40 PM
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pauluk Offline
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Mark,

The chair is more like 2000 to 2500V rather than 25kV. The document I quoted did indeed show that in one case the prisoner's body resistance dropped as low as 133 ohms. (This was Fla. before they pulled the plug.)

On the defib issue, a medical drama show (British) the other night did actually quote 360 joules for the second and third attempts (they didn't mention the energy on the first).

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