safe, twitch, burn or die? refer to the chart

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has anyone else seen this?
 

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Good thing it is probable!

I've been way above their 'fatal' mark, more times than I can remember. I've been respartorily (word?) inhibited at least 3-or 5 times, I think........ minor high voltage (+250-300VDC and over 500VDC), at -least- 50 times. (Tube amps! Gah!) Overall, electrocuted a few hundred times, maybe. Maybe I'm exaggerating. But not by much. I haven't been zapped in, oh..gee..at least a few months. I'm gettin' better at it! (NOT getting electrocuted, that is)

Maybe that's why I can't remember.......
 
The trick is in the the electrical resistance of a human body; it drops rapidly for higher voltages. For example: at 25V, the average resistance is around 3kOhm. For 200V, its less than 15 Ohm. Above 1kV it drops below 1 Ohm, and you are just another conductor...

Then, of course, the resistance depends on the skin area making contact. for 10mm2 the above values are valid. For 100mm2, the values are 10% of that. But: above 200V these factors won't matter anymore.

Calculate the current through your body for the given voltage, and find out wether you will die or not :dead:

Finally, HF currents are more lethal than DC or 50Hz AC. HF currents cause flesh burning without you even feeling it before smelling it. :bigeyes:

Take care
Bakmeel
 
Bakmeel said:
The trick is in the the electrical resistance of a human body; it drops rapidly for higher voltages. For example: at 25V, the average resistance is around 3kOhm. For 200V, its less than 15 Ohm. Above 1kV it drops below 1 Ohm, and you are just another conductor...

Then, of course, the resistance depends on the skin area making contact. for 10mm2 the above values are valid. For 100mm2, the values are 10% of that. But: above 200V these factors won't matter anymore.

Calculate the current through your body for the given voltage, and find out wether you will die or not :dead:

Finally, HF currents are more lethal than DC or 50Hz AC. HF currents cause flesh burning without you even feeling it before smelling it. :bigeyes:

Take care
Bakmeel

If I'm recalling correctly, Nicola Tesla did allot of HF AC experimentation in the late 1800s-early 1900s. Accounts from those who visited his laboratory(s) have been of him passing LARGE amounts of high voltage/high frequency AC over himself & Guests brave enough to be subjected to it..with no harm what so ever.

While I would have loved to have met and talked to the man, I realize that not all of the "Hype" surrounding his life and exploits are 100% true.....Still,
He was Truly, a man WAY ahead of his time.

Tall Shadow
 
"over" is not the same as "through"

when voltages are silly-high and currents low, the juice flows around the outside... that's why schoolkids don't die when they hold hands around the HV generator, and the Van deGraf (sp?) generator won't (always) kill you...
 
Stocker said:
"over" is not the same as "through"

when voltages are silly-high and currents low, the juice flows around the outside... that's why schoolkids don't die when they hold hands around the HV generator, and the Van deGraf (sp?) generator won't (always) kill you...


Yes, HV at very low amperage won't hurt you, but Tesla was using (My understanding) Very High frequency, at High Voltage. It has been described as "lightning dancing all over his body".

I don't know if anyone is doing anything like what he was doing way back then, today. I am not up on what the "State of the art" research in this field is.

Tall Shadow
 
But it is still the current that is dangerous, not the volgate per se. I don't know how Tesla generated the high voltage, but if it was done in such a way that the current was guaranteed to be very small, it wouldn't be dangerous.

It could also be that Tesla did stupid and dangerous experiments and just was very lucky. Some others did and weren't lucky, like Marie Curie.



For DC, I think one must also take the exposure time into consideration. I don't really know, but I would guess one can take higher currents if the exposure time is very short. Why is it that physicians never consider voltage and current for defibrillators, but only the charge? I have a friend who was an EE and then became a physician. He asked about that when doing his cardiology placement, but they either had no answer, or didn't understand the question.
 
Stocker said:
has anyone else seen this?
Yup. But it is not very useful out of context. Specifics as to where the current has to go is missing. This would be through the chest.


KBK said:
Good thing it is probable!

I've been way above their 'fatal' mark, more times than I can remember. I've been respartorily (word?) inhibited at least 3-or 5 times, I think........ minor high voltage (+250-300VDC and over 500VDC), at -least- 50 times. (Tube amps! Gah!) Overall, electrocuted a few hundred times, maybe. Maybe I'm exaggerating. But not by much. I haven't been zapped in, oh..gee..at least a few months. I'm gettin' better at it! (NOT getting electrocuted, that is)

Maybe that's why I can't remember.......

Electrocuted is a one shot deal. Being zapped is not.


Geek said:
Didn't Mythbusters find the actual fatal current to be 6mA at 60Hz?
It does not matter, that result is useless.. How in the world does one go about testing this?

GFI's in the US are designed to not clear at 4mA, and definitely clear at 6.


Stocker said:
1200V 6mA I wouldn't go close to, without it being discharged for a while...;)
Anything below 10mA was considered a class A hazard, categorized with voltage below 50 volts.


Bakmeel said:
The trick is in the the electrical resistance of a human body; it drops rapidly for higher voltages. For example: at 25V, the average resistance is around 3kOhm. For 200V, its less than 15 Ohm. Above 1kV it drops below 1 Ohm, and you are just another conductor...

Then, of course, the resistance depends on the skin area making contact. for 10mm2 the above values are valid. For 100mm2, the values are 10% of that. But: above 200V these factors won't matter anymore.

Where is this resistance variation with applied current documented? I would like to review this.


Stocker said:
"over" is not the same as "through"

when voltages are silly-high and currents low, the juice flows around the outside... that's why schoolkids don't die when they hold hands around the HV generator, and the Van deGraf (sp?) generator won't (always) kill you...
Van De Graaff.

I have a Vandy 2 feet from me as I type. Had ta repair it, it got real wimpy. Turned out the top rollers became coated with rubber from the belt as it aged, there is no triboelectric effect for the seperation of identical materials...

The short circuit current capability of the device is 5 to 10 uAmperes. This is insufficient to kill, even though this vandy produces somewhere around 250 kilovolts.

Of greater concern is the stored energy. Anything over 10 joules is considered as potentially fatal.

Tall Shadow said:

Yes, HV at very low amperage won't hurt you, but Tesla was using (My understanding) Very High frequency, at High Voltage. It has been described as "lightning dancing all over his body".

I don't know if anyone is doing anything like what he was doing way back then, today. I am not up on what the "State of the art" research in this field is.

Tall Shadow

HF high current will be as bakmeel says. Tesla coils are ok as long as the current is not concentrated too much and too long, as in a finger. Put your fingers on a plasma globe, you can feel the heat generated.

BTW, defib's will push between 15 and 30 AMPERES through the chest during the pulse..

Cheers, John
 
Christer said:
Why is it that physicians never consider voltage and current for defibrillators, but only the charge? I have a friend who was an EE and then became a physician. He asked about that when doing his cardiology placement, but they either had no answer, or didn't understand the question.
They consider joules, or stored energy.

The defib has to provide work, in the form of ele energy delivered to the chest. The physicians CANNOT worry about the skin resistivity, the amount of body fat, in a life saving situation. They CANNOT be responsible for setting a voltage and hoping it works, they cannot set a current and hope it works..

By setting the energy total, they specify exactly how much energy is to be placed in the patient. This removes the electrically unknown variables from the physician, allowing them to concentrate on the important stuff.

It doesn't suprise me that physicians could not answer the question. They do not need to know how the device works in detail, just that it does..

Cheers, John
 
jneutron said:

They consider joules, or stored energy.

The defib has to provide work, in the form of ele energy delivered to the chest. The physicians CANNOT worry about the skin resistivity, the amount of body fat, in a life saving situation. They CANNOT be responsible for setting a voltage and hoping it works, they cannot set a current and hope it works..

By setting the energy total, they specify exactly how much energy is to be placed in the patient. This removes the electrically unknown variables from the physician, allowing them to concentrate on the important stuff.

Yes, but already now they set an energy level and hope it works. If it doesn't work they try with more energy. Maybe it is just the total enegy that matters, but I assumed it is the specific combination of current and duration that matters, and that maybe a lower current with longer duration could do the same job with less risk of injuries. With todays technology it should be no problem to design a defib which delivers a specified current for a specified period of time. However, that would mean having two parameters two play with, instead of one, so perhaps that would cause more problems than it would solve. On the other hand, maybe modern defibs work in that way but sense the resistivity to "decide" themselves what trade-off to use?
 
Christer said:


Yes, but already now they set an energy level and hope it works. If it doesn't work they try with more energy. Maybe it is just the total enegy that matters, but I assumed it is the specific combination of current and duration that matters, and that maybe a lower current with longer duration could do the same job with less risk of injuries. With todays technology it should be no problem to design a defib which delivers a specified current for a specified period of time. However, that would mean having two parameters two play with, instead of one, so perhaps that would cause more problems than it would solve. On the other hand, maybe modern defibs work in that way but sense the resistivity to "decide" themselves what trade-off to use?

The old days simply used E = 1/2 C V squared and a honkin cap.

New generation defibs monitor the waveform and calculate the total energy delivered instantaneously, I believe they clip the waveform when the total desired has been delivered. Easily done with an analog multiplier chip, or a 2 channel A/D.

Also, they are trending towards a bipolar pulse instead of a mono. I don't know the details, but bipolar apparently is better.

I recently took defib training here, and the units are smart ones that tell you what to do, monitor the patient's heart, and decide if it will allow you to pulse the patient. If conditions are correct, it will tell you to clear the patient and push the button. Seems the only thing the unit cannot do is keep the onlookers a distance away.

For laypeople as well as doctors, the less decisions that are required in an emergency, the better. The good thing is the stick on pads in the units are compatible to the units the EMT's on site have, so the EMT's may be there by the time you've prepped the patient with the pads.

Cheers, John
 
Thanks for info John,

Yes I suspected the old ones just used a capacitor. I knew the new ones are "smarter" and thought it should be wise to make more parameters adjustable. However, I suppose you are right it might after all be better to leave it to the "stupid intelligence" of a machine to decide on the details. It won't be worse than using the old ones in any case.
 
Christer said:
It could also be that Tesla did stupid and dangerous experiments and just was very lucky.

You're joking, right? Otherwise, to speak like this of one of the greatest minds in human history, in what is called the Year of Tesla, would be sacriligious, bordering on insanity. Just had to say this as I happen to be very proud of my fellow countryman. I apologize for o/t.

Regards,
Milan
 
moamps said:


You're joking, right? Otherwise, to speak like this of one of the greatest minds in human history, in what is called the Year of Tesla, would be sacriligious, bordering on insanity. Just had to say this as I happen to be very proud of my fellow countryman. I apologize for o/t.

Regards,
Milan

No I wasn't joking, but it wasn't meant to speak ill of him. Many of the most famous scientists did dangerous things without realizing what they did, since they were the first to do it. That is why I took Marie Curie as an example. Neither she, nor anybody else at the time, understood quite what radioactivity was or how dangerous it was. That caused her premature death. Still, despite doing such dangerous, and retrospectively foolish, experiments, I think she is the only one who has been awarded two Nobel prizes. Hence, one could hardly call her stupid.
 
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Christer said:
But it is still the current that is dangerous, not the volgate per se. I don't know how Tesla generated the high voltage, but if it was done in such a way that the current was guaranteed to be very small, it wouldn't be dangerous.

It could also be that Tesla did stupid and dangerous experiments and just was very lucky. Some others did and weren't lucky, like Marie Curie.



did you see photographs of his gadgets for HF and HV generating?
seeing that, minuscule current is out of question.

besides,his knowledge (I presumably will not tell-understanding,just because of his own tellings about his "inventing procedures") was waaay in front not just his own time,but even ours.
electricity was not only thing he studied.
...
 
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