| safe, twitch, burn or die? refer to the chart - Click HERE for Original Thread |
| Stocker |
| has anyone else seen this? |
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| KBK |
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....... |
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| maxro |
I suppose you could use this chart to calibrate your body for use as an ammeter? "Well, I would say that I was surprised. So, let's see...1-4 mA." Most usefull, indeed.
Max |
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| Geek |
| Didn't Mythbusters find the actual fatal current to be 6mA at 60Hz? |
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| Stocker |
what, they killed somebody? not very likely if you ask me!
or:
possibly, depending on the voltage. 12V 6mA wouldn't scare me in the slightest!
1200V 6mA I wouldn't go close to, without it being discharged for a while...;) |
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| KBK |
I've been hit by an Electrohome Marquee 'spellman' brand HV supply before.
34.5kV, 11Ma.
Ouch.
That'll get you up in the mornin'!!....or at least give people somebody to look at in a casket. |
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| Bakmeel |
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 |
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| Tall Shadow |
| quote: | Originally posted by Bakmeel
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 |
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| Stocker |
"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... |
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| Tall Shadow |
| quote: | Originally posted by Stocker
"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 |
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| Christer |
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. |
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| jneutron |
| quote: | Originally posted by Stocker
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.
| quote: | Originally posted by KBK
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.
| quote: | Originally posted by Geek
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.
| quote: | Originally posted by Stocker
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.
| quote: | Originally posted by Bakmeel
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.
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Where is this resistance variation with applied current documented? I would like to review this.
| quote: | Originally posted by Stocker
"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.
| quote: | Originally posted by Tall Shadow
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 |
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| jneutron |
| quote: | Originally posted by Christer
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 |
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| Christer |
| quote: | Originally posted by jneutron
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.
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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? |
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| jneutron |
| quote: | Originally posted by Christer
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 |
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| Christer |
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. |
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| moamps |
| quote: | Originally posted by Christer
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 |
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| Christer |
| quote: | Originally posted by moamps
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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| moamps |
As for Tesla, I'm pretty sure he knew what he was doing each step of the way. He was just ahead of his time.
Regards,
Milan |
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| choky |
| quote: | Originally posted by Christer
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.
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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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| Christer |
Milan,
Pleas note I never claimed Tesla didn't know what he was doing, just that it is a possibility. Every scientist in the frontline is necessarily dealing with the unknown to some extent. I am sure Marie Curie also knew what she was doing, to the extent it was reasonably possible for her to know. Even several decades after her groundbreaking research many physicist still didn't realize how dangerous it was and sometims made practical jokes by giving each other "sunburns" using radioactive material. Similar for X-ray. It is said that almost all the nurses who worked on the X-ray deprtatment at one hospital in Stockholm in the 1940's developed stomach cancer later in life. Of course nobody would have exposed them to such danger if anybody had realize it back then.
Similarly, how many thousands patients have died over the years because physicians have had to experiment with treatments for things they still had no knowledge of how to treat. It was unavoidable for the advance of medicine that they made dangerous experiments and that some patients got cured and others died.
I never in any way intended to diminish the excellent scientist Tesla or suggest that he was stupid of foolish. |
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| SY |
| But like many great scientists, he often crossed the border into crackpottery. Like Pauling or Josephson or Crookes. No bad reflection on him, his contributions are legend (and he gets a unit named after him!), it's just that there's something of a Tesla cult out there based on his, ummmm, not-so-great ideas. |
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| Christer |
| quote: | Originally posted by SY
But like many great scientists, he often crossed the border into crackpottery. Like Pauling or Josephson or Crookes. No bad reflection on him, his contributions are legend (and he gets a unit named after him!), it's just that there's something of a Tesla cult out there based on his, ummmm, not-so-great ideas. |
Switching to another famous person. Since you are a physicist (I think), do you know if there is any truth to the story that the otherwise very bright Heisenberg tried to start a nuclear reaction in a cave somewhere in Germany during the war, not realizing how dangerous the experiment was? Or is that just a false rumour? BTW, I am not capable to judge if it would even be possible to get a nuclear reaction started under such circumstances. It is also said that he later told Bohr about this experiment, making Bohr absolutely furious about Heisenbergs stupidity. |
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| moamps |
Nah, it may look like crackpottery while he was in fact just being thorough. You know...searching all venues and stuff... :)
Regards,
Milan |
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| Christer |
| And of course, some of the crackpots have got their crackpot staus revised long after their death, when other reasearchers have finally started to understand them, or prove the things they claimed but couldn't quite prove themselves at the time. |
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| SY |
There were a lot of rumors about Heisenberg. Let's just say "unlikely."
BTW, I was a physicist once, not any more. |
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| Christer |
| quote: | Originally posted by SY
There were a lot of rumors about Heisenberg. Let's just say "unlikely."
BTW, I was a physicist once, not any more. |
Well, I meant you were trained as a physicist. I know you design wine corks nowadays. :)
Yes, I also thought the story sounded unlikely, but I don't have enough knowledge of nuclear physics to judge if it would even be possible. BTW, this story seems to appear in a play about Heisinberg meeting Bohr in Copenhagen some time in 1941/42. AFAIK this meeting actually took place in reality, but how much else of it is based on reality, I have no idea of. |
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| SY |
| A fun thing to ask a physicist with a background in QM is, "What did Bohr actually DO?" |
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| Christer |
| quote: | Originally posted by SY
A fun thing to ask a physicist with a background in QM is, "What did Bohr actually DO?" |
Here in Sweden we say: "If you say A, you must also say B".
So for us lacking the sufficient background, what would the physicist answer? Or what would a reasonable answer be? Did Bohr even do anything on QM? |
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| SY |
| It's a damn good question and one I don't know the answer to. The "Bohr Model" was an early and ad hoc attempt to explain electrons in atoms and lasted maybe 5 years before being supplanted. The Copenhagen interpretation is dime-store philosophy, not science. So... I really don't know. |
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| Christer |
| quote: | Originally posted by SY
It's a damn good question and one I don't know the answer to. The "Bohr Model" was an early and ad hoc attempt to explain electrons in atoms and lasted maybe 5 years before being supplanted. The Copenhagen interpretation is dime-store philosophy, not science. So... I really don't know. |
OK, but wasn't it least an improvement over the Rutherford model at the time it was introduced. I guess Bohr couldn't possibly foresee that QM would make his model somewhat obsolete a few years later. But I am on thin ice here. I don't even quite remember exactly what those two models look like and how they differ. |
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| KBK |
I'm interested in anything Tesla did that was considered crackpot. New stuff is in the dark coners, not the places you've already looked. You know that, Sy. On the other hand, I've no idea what it is (or I might, duunno) that you guys speak of.
And what was that particular thing or avenue? I'm all curious-aquiver now.
Spill da beans. |
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| SY |
| I don't debate creationism or Tesla cults. :D |
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| Tall Shadow |
| quote: | Originally posted by SY
I don't debate creationism or Tesla cults. :D |
I can agree with your stance on debating just about any religion over the net. As far as "Tesla Cults", or even worse, the "Edison Cults" I've had the misfortune to run in to....Yikes! :bigeyes:
I'd also agree that along with the normal "Students" and people just wanting to know/understand the "Who/What/Why" of things......There sure are some Wacky people in this world!.....:bigeyes:
Me, I'm just crazy! ;)
Tall Shadow |
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| KBK |
so I guess I have to google tesla cults? :p
I'd imagine that Edison Cults would be rather boring. Awful meetings, I'd wager. Reminiscent of Vogon Poetry readings.
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"I contend that we are both atheists. I just believe in one fewer god than you do."
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"Don't you believe in an ineffiable truth?"
"You mean Google?"
:p :p |
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| Tall Shadow |
| quote: | Originally posted by KBK
so I guess I have to google tesla cults? :p |
:D I don't know what would come up, but imagine every "Free Energy" & "Perpetual Motion" crazy'ness that you have ever seen, heard about or read x10!
| quote: | Originally posted by KBK
I'd imagine that Edison Cults would be rather boring. Awful meetings, I'd wager. Reminiscent of Vogon Poetry readings. |
You almost cost me a new monitor with that last line... ;)
Actually, a good many (if not most) of the present day schools teach about "The Wizard of Menlow Park" as he is/was called. They tell of all of the great "Inventions" that he "Thought up", when he was only (IMHO) actually a mildly inventive man, more prone to stealing his "Great discoveries", or standing on the shoulders of giants to reach them...and then only by using "brute-force inventing"...then when finished, disavowing any of their contributions.
As i found quoted one day looking through Lindsay Books
(Loosely transcribed here)
"Don't beat your head against it till it works like Edison would, do some calculations first, like Tesla."
| quote: | Originally posted by KBK
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"I contend that we are both atheists. I just believe in one fewer god than you do."
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"Don't you believe in an ineffiable truth?"
"You mean Google?"
:p :p |
Like I said, while I can agree that none of the current "Religions" have "it" correct.
I (A.) Can't believe that there in the VASTNESS of space that there isn't something "Better/Higher/More God-Like" than us.
And (B.) We have any where near an Idea of what is really going on in the Universe.
And Finally...
NEVER try to argue religion over the net......I can't think of a bigger waste of time that that.........except maybe....SOCCER! ;) :devilr: ;) Just Kidding! Europe!!!!
Tall Shadow |
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| TwoSpoons |
back on topic ...
When I was designing electric fence energisers we used a current / time curve called the 'C2 Line'. Under was 'safe', over was not.
Basically it related pulse duration to peak current. IIRC the maximum duration was limited to 10ms at some mA, the maximum current was 15.5A for 100us. The line represented the current/time combination that had a 1 in 170,000 chance of causing fibrillation. This was based on a human body resistance of 500R - though in practise it was more like 800R.
The biggest energiser I designed would deliver a 10kV, 100uS pulse, with 36J backing it up. Right up at the C2 limit ... |
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| Geek |
| quote: | Originally posted by jneutron
It does not matter, that result is useless.. How in the world does one go about testing this? |
Well, watch the episode ;) :rolleyes: |
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