dudek@ai.toronto.edu (Gregory Dudek) (06/09/89)
I noticed long ago that if you (accidentally) touch a live
conductor, there is an odd sensation reminicent of a rough surface.
For example, I've noticed a short to a wall-switch faceplate recently
by observing that if you touched the faceplate it had that
"rough-ish" feel instead of feeling smooth (the feeling is kind
of line a high-freq. vibration -- 60Hz?). You have to run your
finger along to conductor to notice the sensation. This feeling goes away
when you cut the power, so it's not due to a real change in the
surface of the conductor.
Does anybody have a good explanation for this phenomenon?
Greg Dudek
--
Dept. of Computer Science (vision group) University of Toronto
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ARPA: user%ai.toronto.edu@relay.cs.nethoward@tp2.Waterloo.NCR.COM (Howard F. Steel) (06/09/89)
In article <89Jun8.160452edt.10877@ephemeral.ai.toronto.edu> dudek@ai.toronto.edu (Gregory Dudek) writes: > I noticed long ago that if you (accidentally) touch a live >conductor, there is an odd sensation reminicent of a rough surface. >For example, I've noticed a short to a wall-switch faceplate recently >by observing that if you touched the faceplate it had that >"rough-ish" feel instead of feeling smooth (the feeling is kind >of line a high-freq. vibration -- 60Hz?). It is indeed the 60 Hz from the power source. The "rough" sensation you feel is leakage current, well below 3.5 mA (probably in the neighbourhood of 500 uA), from the power source through your body to ground or lower potential level. >You have to run your >finger along to conductor to notice the sensation. This feeling goes away >when you cut the power, so it's not due to a real change in the >surface of the conductor. As you move your hand along the conductor you apply varying pressure on it which will result in varying amounts of leakage current as the contact resistance between you and the conductor increases or decreases. It will go away when the power is removed, because the voltage differential which results in the leakage current is no longer available. If the sensation remains after the power is removed, then the circuit is connected to some device that will store energy (ie a coil or a capacitor) -- Howard.Steel@Waterloo.NCR.COM :-( I Think, Therefore I AM, aka: Howard "The Duck" Steel :-) I think
kencr@haddock.ima.isc.com (Kenny Crudup) (06/09/89)
In article <89Jun8.160452edt.10877@ephemeral.ai.toronto.edu> dudek@ai.toronto.edu (Gregory Dudek) says: > I noticed long ago that if you (accidentally) touch a live >conductor, there is an odd sensation reminicent of a rough surface. > Does anybody have a good explanation for this phenomenon? > Greg Dudek "Skin effect"?? :-) -- Kenneth R. Crudup, Contractor, Interactive Systems, Cambridge MA So what if the meek end up with the earth- we'll just kick their butts and take it back! E-Mail, (which tends not to be delivered :-( ) Phone (617) 661 7474 x238 {encore, harvard, spdcc, think}!ima!haddock!kencr kencr@haddock.ima.isc.com
hermann@cpsc.ucalgary.ca (Michael Hermann) (06/10/89)
In article <89Jun8.160452edt.10877@ephemeral.ai.toronto.edu> dudek@ai.toronto.edu (Gregory Dudek) writes: > > I noticed long ago that if you (accidentally) touch a live >conductor, there is an odd sensation reminicent of a rough surface. > (the feeling is kind >of line a high-freq. vibration -- 60Hz?). I'm assuming that besides doing this by accident, you were very well insulated and so your body did not provide a ground fault to the conductor (ie. no current went a significant distance through you). I've done the same thing, and I think that it must be a sensory distortion caused by the conductor current. Part of your finger becomes a current carrier, but only at the surface, just as with any other conductor. The tactile nerves in the skin could then be overloaded, to the tune of about 60Hz, and provide you with the illusory sensation of a 60Hz vibration in the conductor you are touching. I can't explain why the nerves concerned with detecting pain or temperature changes are not similarly stimulated. If you are unfortunate enough to unplug a lamp the _wrong_ way, you will find that your hand and lower arm are subject to a much more palpable _thrumming_ at about 60Hz, which is partly the current, but mostly you arm and hand muscles being stimulated by the current and contracting at 60 Hz. This is an unpleasant sensation, but not painful at all; once is enough however. | Mike Hermann | ..!uunet!ubc-cs!calgary!hermann calgary!hermann@cs.ubc.ca Organized Religion is like Organized Crime; it preys on peoples' weakness, generates huge profits for its operators, and is almost impossible to eradicate. -- me
sparks@corpane.UUCP (John Sparks) (06/15/89)
In article <89Jun8.160452edt.10877@ephemeral.ai.toronto.edu> dudek@ai.toronto.edu (Gregory Dudek) writes: > > I noticed long ago that if you (accidentally) touch a live >conductor, there is an odd sensation reminicent of a rough surface. > Does anybody have a good explanation for this phenomenon? > Never happened to me. The few times I accidently touched a hot wire I either a> got the shit shocked out of me :-) b> got a tingling sensation, like when your hand falls asleep. A> was because I was grounded fairly well and B> was becasue I wasn't. Be careful and don't fool around with electricity. It CAN kill you. -- John Sparks | {rutgers|uunet}!ukma!corpane!sparks | D.I.S.K. 24hrs 1200bps ||||||||||||||| sparks@corpane.UUCP | 502/968-5401 thru -5406 You are in a maze of twisty little passages, all alike.
flash@lopez.UUCP (Gary Bourgois) (06/16/89)
From article <1496@cs-spool.calgary.UUCP>, by hermann@cpsc.ucalgary.ca (Michael Hermann): > In article <89Jun8.160452edt.10877@ephemeral.ai.toronto.edu> dudek@ai.toronto.edu (Gregory Dudek) writes: >> >> (the feeling is kind >>of line a high-freq. vibration -- 60Hz?). I have noticed this phenomenon for years, not just with conductors but with a lot of commercially available equipment. The sensation is as if the surface of the item in question is "sticky-buzzy"(tm) and a finger moved over the surface of such an item seems to vibrate at the 60 hz (In North America) line frequeny. One such device is the SONY ICF-2010 shortwave radio, when operated with the 4.5v AC Supply, when touching some of the metal parts on the radio during AC operation. It is not just a defective set, as I have owned THREE of them, and each had this phenomena. For the record, I am one of those persons who perspire a conductive material (oil based) from the fingers.. i.e. I leave good fingerprints. Other equipment I have owned also produces the effect. -- | Gary Bourgois flash@lopez.UUCP ..rutgers!mailrus!sharkey!lopez!flash | | Great White North UPLink, Marquette Michigan | | NATIONWIDE AMATEUR RADIO (1500 watts on 3950) --- nightly after 0200z | |___________________WB8EOH - The Eccentric Old Hippie____________________|
bruce@ssc-vax.UUCP (Bruce Stock) (06/17/89)
In article <814@corpane.UUCP>, sparks@corpane.UUCP (John Sparks) writes: > In article <89Jun8.160452edt.10877@ephemeral.ai.toronto.edu> > dudek@ai.toronto.edu (Gregory Dudek) writes: > > > > I noticed long ago that if you (accidentally) touch a live > >conductor, there is an odd sensation reminicent of a rough surface. > > Does anybody have a good explanation for this phenomenon? > > > I have experienced the sensation you mention many times. Usually when touching metal cased equipment (radio, HI-FI, etc) which has leaky bypass capacitors on the AC line. Reversing the plug in the wall usually cures it. Sure is an interesting sensation, tho. Bruce Stock
clw@hprnd.HP.COM (Carl Wuebker) (06/20/89)
To Gary, who owns the ICF-2010 with the potentially 'hot' chassis --
Several electronics products connect each leg (hot and neutral) of the
AC line to the chassis/green-wire ground with "Y" capacitors to reduce
conducted EMI. If a product like this isn't grounded (i.e. the green-wire
ground is broken at any point), the capacitors divide the AC line voltage
in half and the chassis floats at half line voltage (65v).
I consider a 'buzz' from any equipment pretty serious, and I recommend
tracking down and fixing the cause of the problem.
Good luck,
Carl "nearly killed by a 'grounded' drill once" Wuebker
clw@hprnd * HP Roseville Networks Division * (916) 785-4296davidc@vlsisj.VLSI.COM (David Chapman) (06/20/89)
In article <1496@cs-spool.calgary.UUCP> hermann@cs-sun-fsd.UUCP (Michael Hermann) writes: >In article <89Jun8.160452edt.10877@ephemeral.ai.toronto.edu> dudek@ai.toronto.edu (Gregory Dudek) writes: >> >> I noticed long ago that if you (accidentally) touch a live >>conductor, there is an odd sensation reminicent of a rough surface. >> (the feeling is kind >>of line a high-freq. vibration -- 60Hz?). > > I'm assuming that besides doing this by accident, you were very well >insulated and so your body did not provide a ground fault to the conductor >(ie. no current went a significant distance through you). My understanding of the whole business is that you are feeling the current which is (dis)charging your body capacitance. Pump a few electrons in and you get a current. You don't need a current "through" your body. There's a lot of mass there in which to store excess electrons. A corollary to this is that you don't need to be grounded to get zapped by a _very_ high voltage (>100 kV?). Corrections welcome; flames (sparks?) to /dev/null. -- David Chapman {known world}!decwrl!vlsisj!fndry!davidc vlsisj!fndry!davidc@decwrl.dec.com
sparks@corpane.UUCP (John Sparks) (06/22/89)
In article <632@lopez.UUCP> flash@lopez.UUCP (Gary Bourgois) writes: >One such device is the SONY ICF-2010 shortwave radio, when operated with >the 4.5v AC Supply, when touching some of the metal parts on the radio >during AC operation. It is not just a defective set, as I have owned THREE >of them, and each had this phenomena. It might not be the set, it might be faulty AC wiring in your house. No consumer electronics is designed to be "hot". If it is and you have noticed this on other sets, then maybe your neutral wiring in your outlet is reversed to normal (on the wrong side of the outlet) or is not grounded properly. >For the record, I am one of those persons who perspire a conductive >material (oil based) from the fingers.. i.e. I leave good fingerprints. shouldn't make a diff. The equipment shouldn't be "hot" to begin with. >Other equipment I have owned also produces the effect. See? sounds like a wiring problem. -- John Sparks | {rutgers|uunet}!ukma!corpane!sparks | D.I.S.K. 24hrs 1200bps ||||||||||||||| sparks@corpane.UUCP | 502/968-5401 thru -5406 I'm the person your mother warned you about.
sparks@corpane.UUCP (John Sparks) (06/22/89)
<814@corpane.UUCP> <427@edai.ed.ac.uk> Sender: Reply-To: sparks@corpane.UUCP (John Sparks) Followup-To: Distribution: Organization: Corpane Industries, Inc. Keywords: touch, sensation, live, shock, dumb, dead In article <427@edai.ed.ac.uk> cam@edai (Chris Malcolm) writes: / Hence it can only be detected when /very lightly brushing the surface. That's all just my guess. I've used /the effect for 30 years to detect live mains by touch. It works best on /shiny surfaces, stroked slowly with a very light touch. It is not a /reliable indicator of _connection_ to live mains, however: the feeling /also occurs in metal connected only capacitatively (i.e. by adjacency) /to live metal. It _is_ a reliable indicator of something not being /earthed, however. The buzz (roughness) is the AC frequency. / /Not recommended unless you don't mind the occasional jolt from the /mains, which probably means your skin ought to be on the dry side. I'm /talking about 250V mains, by the way. 120 is less lethal. ^^^^! Er, not wanting to flame you... but that's stoopid! Why do you want to risk your life? That's exactly what you are doing by touching live 250VAC. It only takes milliamps to stop a heart. The current is passing from your hand to ground (probably your feet), and passing by your heart on the way down. / /-- /Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550 /Department of Artificial Intelligence, Edinburgh University ^^^^^^^^^^^^^^^^^^^^^^^ Maybe you should invest in some? -- John Sparks | {rutgers|uunet}!ukma!corpane!sparks | D.I.S.K. 24hrs 1200bps ||||||||||||||| sparks@corpane.UUCP | 502/968-5401 thru -5406 I'm the person your mother warned you about.
phil@ux1.cso.uiuc.edu (06/23/89)
An interesting question is why this leakage current is felt only when the finger is moved across the surface, and not at all (or in some cases less so) when pressing in one place. I suspect it might that the leakage current, as small as it is, is actually relatively high for the cross section it is passing through when the touch is very light. It is a high cross sectional current, causing very small amounts of tissue to react to it. Thus the feeling is not painful, but is usually obvious. I feel it very readily, but have known people who touch when I do and cannot feel it at all. I one piece of equipment, I readily felt it very often. One day I accidently touched something else while touching it... ***ZZZZZAP***. I found it had one side of the AC connected directly to the chassis. Although an isolation transformer would have cured it, I chose what happened to be for me the less costly approach: I scrapped it for parts. --Phil howard-- <phil@ux1.cso.uiuc.edu>
fiesta@cbnewsi.ATT.COM (eric.c.beck) (06/23/89)
> Not recommended unless you don't mind the occasional jolt from the > mains, which probably means your skin ought to be on the dry side. I'm > talking about 250V mains, by the way. 120 is less lethal. From what little I've been taught about electrical shocks and resuscitation I seem to remember that 120 was actually "more lethal" than 240 ... something to do with fibrillation (from a 120 shock) versus complete stoppage of the heart with a 240 volt shock. (It is harder to resuscitate an individual in fibrillation(?)). I would suspect this all this depends on the current through the heart muscle. Perhaps someone applied Ohm's law with some practical values for body resistance, etc. Eric Beck fiesta@homxb.att.com
john@zygot.UUCP (John Higdon) (06/23/89)
In article <842@corpane.UUCP>, sparks@corpane.UUCP (John Sparks) writes: > In article <632@lopez.UUCP> flash@lopez.UUCP (Gary Bourgois) writes: > >One such device is the SONY ICF-2010 shortwave radio, when operated with > >the 4.5v AC Supply, when touching some of the metal parts on the radio > >during AC operation. It is not just a defective set, as I have owned THREE > >of them, and each had this phenomena. > > It might not be the set, it might be faulty AC wiring in your house. > No consumer electronics is designed to be "hot". If it is and you have noticed > this on other sets, then maybe your neutral wiring in your outlet is reversed > to normal (on the wrong side of the outlet) or is not grounded properly. Almost all ungrounded consumer equipment has a small amount of leakage that you can feel, especially if you run the back of your finger over metal surfaces. In the case of the Sony ICF-2010, the primary to secondary capacitance in the AC adaptor is the culprit. This leakage is quite small and totally harmless. The wiring in your house may or may not be faulty (I suspect not) since that has nothing to do with what you are observing. Besides, the ICF-2010 adaptor plug is non-polarized so it can be inserted either way into the outlet. You will note that the leakage is there regardless of which way you plug it in. BTW, since most electronic equipment has this leakage and people find it annoying, most office, industrial, and educational equipment is third-wire gounded. This also prevents "additive leakage". -- John Higdon | P. O. Box 7648 | +1 408 723 1395 john@zygot.uucp | San Jose, CA 95150 | M o o !
myers@hpfcdj.HP.COM (Bob Myers) (06/24/89)
>/Not recommended unless you don't mind the occasional jolt from the >/mains, which probably means your skin ought to be on the dry side. I'm >/talking about 250V mains, by the way. 120 is less lethal. ^^^^! >Er, not wanting to flame you... but that's stoopid! Why do you want to risk >your life? That's exactly what you are doing by touching live 250VAC. It only >takes milliamps to stop a heart. The current is passing from your hand to >ground (probably your feet), and passing by your heart on the way down. One should never try to stand in the way of evolution. :-) Bob Myers | "One man's "magic" is another man's engineering. myers%hpfcla@hplabs. | "Supernatural" is a null word." hp.com | - Lazarus Long/Robert A. Heinlein
cam@edai.ed.ac.uk (Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550) (06/24/89)
In article <843@corpane.UUCP> sparks@corpane.UUCP (John Sparks) writes: >In article <427@edai.ed.ac.uk> cam@edai (Chris Malcolm) writes: >/Not recommended unless you don't mind the occasional jolt from the >/mains, which probably means your skin ought to be on the dry side. I'm >/talking about 250V mains, by the way. 120 is less lethal. > ^^^^! >Er, not wanting to flame you... but that's stoopid! Why do you want to risk >your life? That's exactly what you are doing by touching live 250VAC. It only >takes milliamps to stop a heart. The current is passing from your hand to >ground (probably your feet), and passing by your heart on the way down. I was talking about feeling a faint sensation when touching live mains with one hand while no other part of the body is grounded. The current in this case is so trivial that some people can't actually detect it. As to the heart-stopping bit, since I was told that I've been careful to keep one hand in my pocket when playing with live mains with the other, in order to stop the current going through the heart. But, like lots of other people I know, I have had a few dozen 250V shocks from one hand to the other, which would seem likely to pass through the heart, and it didn't stop, or give any evidence of upset. In the days of AC and DC in the UK some electricians would routinely discover whether a house supply was AC or DC by sticking their fingers into a live light socket. The resistance of the body is largely due to the skin contact points, and is considerably affected by contact area and dampness. It changes by orders of magnitude as you pass from light touch to strong grip. Next time I'm near appropriate equipment I'll measure my ranges of resistance to these kinds of voltages and tell you, but I suspect the dangers of _light_ touch with _dry_ skin are much exaggerated - as they should be, for the sake of general safety. -- Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550 Department of Artificial Intelligence, Edinburgh University 5 Forrest Hill, Edinburgh, EH1 2QL, UK
ghg@pur-ee.UUCP (George Goble) (06/25/89)
Back when I was 5 or 6, I noticed our kitchen oven was "fuzzy". We had 5 miles of electric fence on our farm (2000V @ 25 MA, 1 sec on, 1 sec off). There were electric fence testers around, which just amounted to an NE-2 neon bulb (no limiting resistor) and one long ground wire tied to a "nail" which you grounded while touching the other end to the fence. The brightness gave an indication of the condition of the fence. My mom did not notice this fuzzy effect, so I had to "convince her". Suspecting the fuzzy feeling might be electricity leakage (I had run into similar feelings on the electric fence when I was very poorly grounded), I took the fence tester, touched one end to the sink (good ground), and the other end to the oven to see if it would glow. Well, it did, very bright purple-white for about 1 second, then it exploded (no limiting resistor) into a fireball in my hand. (I was not hurt) mom started screaming, etc. She also didn't like the holes which were burned into both the sink and the oven (about 1/4"-1/2" I remember). I told her "that could have been you.. if you happened to touch both the sink and oven at the same time". She quit complaining after that. This was a new (just built) house in the late '50s. So much for wiring codes/inspections back then. REMC gave us "gold medalion" for this house as it was one of the first "all electric" homes in the county, had a separate electic meter for the heat for some cost study. Also the oven was on a 30A or 40A circuit breaker. Back in the 50's those breakers seemed to take forever to blow, hence the fireball. --ghg Geo. Goble, Engineering Computer Network, Purdue U. W. Lafayette, IN 47907
torkil@psivax.UUCP (Torkil Hammer) (06/27/89)
You are discussing 3 different things. One is an electrical shock, as you can get from touching a live 110 or 220 V wire. Usually those shocks are not lethal, but if you stand on a wet grounded concrete floor and/or get them through the heart they can be. The second (original posting) is a capacitative coupling between equipment (lamps, stereos, appliances) and you. The coupled voltage can be high - up to the line voltage and possibly higher, but the generator impedance is several megaohms, so the fuzzes don't harm you. The fuzzes can be induced by microamps, but not everybody can feel them. I experienced the fuzz the first time from a well insulated lamp on a wooden table. It went away when I reversed the plug, but much to my surprise the proper position of the plug depended on the position of the lamp on the table. Which goes to prove that the effect is not ohmic conductive, but must be of proximity coupling nature. The fuzzes are difficult to reproduce, because you need just the right skin resistance to make them work. You also need the right muscle tension. I think they work by having a small current trigger muscles nerves that are already biased. The third is the jolts you get from cattle fences. These are kilovolts delivered through an impedance high enough to make it safe in most situations. Because the source impedance is very high, the fence delivers a current that does not depend on how well you are grounded - the jolt is the same whether you stand on dry or wet soil, though if you grip the fence you can get your skin resistance so low that you barely feel the jolt - the most of the current bypasses along the surface of your skin. Warning: Don't pee on an electric fence. The shock passes directly through rather sensitive body parts. The jolt can knock you unconscious and possibly do some internal damage. Finally, don't play with neon bulbs without limiting resistors. The bulb is started with a peak voltage of 90-165 volts or so, but then enters a negative impedance region where an applied voltage of low impedance can make the thing explode with sparks of white-hot bits of metal coming out through the soldered end. These sparks can burn holes in carpets, hands, eyes and whatever else gets in the way. A limiting resistor of 220 kohms is standard for 110-220 VAC applications. If you want to check the house wiring, you can (at least in USA) buy a 3-pronged gadget that contains 4 neon bulbs arraigned in a pattern that can detect most miswirings including reversed and disconnected wires. torkil
snoopy@sopwith.UUCP (Snoopy) (07/16/89)
In article <322@cbnewsi.ATT.COM> fiesta@cbnewsi.ATT.COM (eric.c.beck) writes: |> Not recommended unless you don't mind the occasional jolt from the |> mains, which probably means your skin ought to be on the dry side. I'm |> talking about 250V mains, by the way. 120 is less lethal. | |From what little I've been taught about electrical shocks and resuscitation |I seem to remember that 120 was actually "more lethal" than 240 ... something |to do with fibrillation (from a 120 shock) versus complete stoppage of the |heart with a 240 volt shock. (It is harder to resuscitate an individual |in fibrillation(?)). From _Electronic Components and Measurements_ by Bruce D. Wedlock and James K. Roberge, based on an article entitled "The Fatal Current," originally published by Fluid Controls Corporation: "...currents between 100 and 200mA are lethal. In this current range, ventricular fibrillation of the heart occurs. Above 200mA, the resulting muscular contractions are so severe that the heart is forcibly clamped during the shock, and ventricular fibrillation is prevented. Thus, although severe burns, unconsciousness, and stoppage of breathing occur, the shock is not usually fatal if the victim is given immediate resuscitation or artificial respiration. [...] The actual body resistance varies depending on the points of contact and the condition of the skin. The total resistance may be as low as 1kOhm for wet skin and as high as 500kOhm for dry skin. Death by electrocution as been recorded from a voltage as low as 42 volts DC, implying a resistance as low as 400 Ohms." There is a chart showing "threshold of sensation" at about 0.002A, "painful" at about 0.01A, "cannot let go" at about 0.02A, "extreme breathing difficulties" at about 0.08A, "death" from 0.1A to 0.2A, "breathing stops" at about 0.3A, and "severe burns" at about 0.4A. "*action in case of shock* [...] The resistance of the victim's contact decreases with time so that the fatal 100- to 200-mA current may be reached if action is delayed. If the victim is unconscious and has stopped breathing, start artificial respiration *at once. Do not stop resuscitation until a medical authority has pronounced the victim beyond help.* It may take as long as eight hours [ !!! ] to revive the patient." Is it time for a frequently-asked-questions list for this group? _____ .-----. /_____\ Snoopy ./ RIP \. /_______\ qiclab!sopwith!snoopy | | |___| parsely!sopwith!snoopy | tekecs | |___| sun!nosun!illian!sopwith!snoopy |_________|
cam@edai.ed.ac.uk (Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550) (07/22/89)
In article <89Jun8.160452edt.10877@ephemeral.ai.toronto.edu> dudek@ai.toronto.edu (Gregory Dudek) writes: > > I noticed long ago that if you (accidentally) touch a live >conductor, there is an odd sensation reminicent of a rough surface. > Does anybody have a good explanation for this phenomenon? > I've always presumed it was a very slight shock due to the very slight leakage from the body, e.g., the way one can light a neon test screwdriver by tounching one end to live and the other to you. The current is so slight as to only be perceptible when it is communicated through a very small contact patch. Hence it can only be detected when very lightly brushing the surface. That's all just my guess. I've used the effect for 30 years to detect live mains by touch. It works best on shiny surfaces, stroked slowly with a very light touch. It is not a reliable indicator of _connection_ to live mains, however: the feeling also occurs in metal connected only capacitatively (i.e. by adjacency) to live metal. It _is_ a reliable indicator of something not being earthed, however. The buzz (roughness) is the AC frequency. Not recommended unless you don't mind the occasional jolt from the mains, which probably means your skin ought to be on the dry side. I'm talking about 250V mains, by the way. 120 is less lethal. -- Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550 Department of Artificial Intelligence, Edinburgh University 5 Forrest Hill, Edinburgh, EH1 2QL, UK
hgw@julia.math.ucla.edu (Harold Wong) (08/03/89)
In article <427@edai.ed.ac.uk> cam@edai (Chris Malcolm) writes: > >very lightly brushing the surface. That's all just my guess. I've used >the effect for 30 years to detect live mains by touch. It works best on >shiny surfaces, stroked slowly with a very light touch. It is not a WOW! I can't believe you just said that. Please don't do that, it's dangerous. Please play it safe and use other methods such as a vold meter or the neon bulb. One day you'll find yourself touching ground and you'll get electrocuted. Please my friend, we don't want to hear about your death. > >Not recommended unless you don't mind the occasional jolt from the >mains, which probably means your skin ought to be on the dry side. I'm >talking about 250V mains, by the way. 120 is less lethal. It doesn't matter wether it's 120 or 220, They're both lethal. It's not the volts that kill, it's the amps. > >-- >Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550 >Department of Artificial Intelligence, Edinburgh University >5 Forrest Hill, Edinburgh, EH1 2QL, UK ------------------------------------------------------------------------------- Harold Wong (213) 825-9040 UCLA-Mathnet; 3915F MSA; 405 Hilgard Ave.; Los Angeles, CA 90024-1555 ARPA: hgw@math.ucla.edu BITNET: hgw%math.ucla.edu@INTERBIT
myers@hpfcdj.HP.COM (Bob Myers) (08/05/89)
> It doesn't matter wether it's 120 or 220, They're both > lethal. It's not the volts that kill, it's the amps. Y'know, that last is said often enough that people are starting to repeat it as Holy Writ without actually understanding it. Yes, it is the amount of current passing through the body (particularly the heart itself) which determines whether or not you'll just get a tingle, or wind up as a customer of the local coroner. However, the Gospel According to Saint Ohm says that voltage and current are related, and so we should all keep in mind that a high voltage source is more likely to kill than a low voltage source. 120 and 220 ARE both *potentially* (no pun intended) lethal, but you're more likely to get into trouble with 220 - as it can force a deadly current through a higher-impedance load, meaning that you don't have to be in *quite* as good contact as you would need to check out for good on 120. I = E/R, so any time you set up a situation where you can get 100 mA through the heart, well, please smile and leave a happy-looking corpse. The rules to follow - keep one hand in your pocket at all times, and make SURE the damn thing is unplugged before you work on it! Related anecdote: In my more naive younger days, I was working on a Gazillion-amp +5V supply with a friend. The filter caps were the size of Foster's beer cans, and so I wanted to take the precaution of making sure that they were discharged. I asked my able associate if he'd unplugged the supply, and, getting an affirmative response, proceeded to whack the caps with a Craftsman screwdriver, size Enormous. ZZZZZZZOTTTTTTT!!!! "Well, gee, that one was pretty well charged up! Better whack it again!" ZZZZOTTTTTTT!!!! About this time, I asked my partner in crime if he was SURE he'd unplugged the supply. By way of response, he simply held up the end of the cord so that I could see for myself that yes, the damn thing WAS unplugged, stop bothering me. Well, I continued to whack away at the capacitors, drawing some really nifty-looking arcs and pitting the living hell out of the screwdriver shaft in the process. (Yes, you too can learn arc-welding in the comfort of your own lab!) Finally, I decided to grab the voltmeter we were using to see for myself if any charge was remaining. The needle stayed at zero. Actually, BELOW zero. Right on the peg, in fact. My gaze ran along the back of the bench, while continuing to disintegrate my screwdriver. Rob had actually unplugged the voltmeter. Bob Myers | "One man's "magic" is another man's engineering. myers%hpfcla@hplabs. | "Supernatural" is a null word." hp.com | - Lazarus Long/Robert A. Heinlein
cam@edai.ed.ac.uk (Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550) (08/05/89)
I'd like to thank all those kind people who have expressed concern for
my continued existence, given my habit of touching live wires to see if
they are live. Snoopy (snoopy@sopwith.UUCP) kindly provided these facts:
From _Electronic Components and Measurements_ by Bruce D. Wedlock and
James K. Roberge, based on an article entitled "The Fatal Current,"
originally published by Fluid Controls Corporation:
"...currents between 100 and 200mA are lethal... The actual body
resistance varies depending on the points of contact and the condition
of the skin. The total resistance may be as low as 1kOhm for wet skin
and as high as 500kOhm for dry skin."
Well, as I promised, I tested my resistance. As I said I have dry skin.
With a light touch. such as I use for testing mains, my resistance is
>10MOhm. If I dampen my fingers by breathing on them, and grab the test
prods painfully firmly, I can bring it down to around 10KOhm. That's
still an order of magnitude under the lethal current. So you all kind
folks can stop worrying about me! As a matter of fact, the kind of jolts
I sometimes inadvertently get from the mains are not as severe as the
jolts I can get from old diathermy machines, which doctors used to use
to administer therapeutic shocks to gullible patients. Nor are they as
severe as holding an electric fence of the cattle retaining kind.
Does anyone know what would happen if one inadvertently, one rainy
night, with wet feet, pissed onto an electric fence?
--
Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550
Department of Artificial Intelligence, Edinburgh University
5 Forrest Hill, Edinburgh, EH1 2QL, UK pmb@swituc.UUCP (Pat Berry) (08/06/89)
In article <427@edai.ed.ac.uk>, cam@edai.ed.ac.uk (Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550) writes: > very lightly brushing the surface. That's all just my guess. I've used > the effect for 30 years to detect live mains by touch. It works best on > shiny surfaces, stroked slowly with a very light touch. It is not a > Not recommended unless you don't mind the occasional jolt from the > mains, which probably means your skin ought to be on the dry side. I'm > talking about 250V mains, by the way. 120 is less lethal. > -- > Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550 > Department of Artificial Intelligence, Edinburgh University > 5 Forrest Hill, Edinburgh, EH1 2QL, UK Like they say, don't try this at home!!! What Chris does not mention is that it only takes 100 ma (read that one tenth of an amp) to kill you! At that current flow, your heart fribilates (shakes itself apart). Above that current flow, the heart plain stops. Why risk your life when you can buy a small voltmeter for under $15.00 in most hardware stores? Please do not ever touch a wire to see if it is hot. Such advice is not only dangerous, it is criminal. You risk dying on the off chance your skin resistance is high enough to prevent the flow of a lethal amount of current through your body. 120 volts will kill you just as fast as 240 volts. If your body presents as much as 1100 ohms of AC resistance to the 110 volt circuit, you will pass the lethal 100ma of current! Come on guys, lets not kill off the readers with poorly thought out postings. -- Pat Berry KN7B pmb%swituc.uucp@arizona.edu KN7B @ WB7TLS.AZ packet radio
ankleand@mit-caf.MIT.EDU (Andrew Karanicolas) (08/06/89)
>Well, as I promised, I tested my resistance. As I said I have dry skin. >With a light touch. such as I use for testing mains, my resistance is >>10MOhm. If I dampen my fingers by breathing on them, and grab the test >prods painfully firmly, I can bring it down to around 10KOhm. That's >still an order of magnitude under the lethal current. So you all kind >folks can stop worrying about me! As a matter of fact, the kind of jolts You are placing yourself at immense risk. You are making several DEAD WRONG ASSUMPTIONS. You measured your resistance but thats only part of the story. You really need to measure the IMPEDANCE of your body at the frequency of interest (50 to 60Hz). You will find that this impedance is quite different from DC measurement you made. I recall being told that 60Hz just about minimizes the impedance of the body. The other seriously wrong assumption you are making also concerns itself with the order of magnitude of the impedance: you measured the resistance between your finger tips. While using your fingertips to sense mains voltage, you may expose another part of your body to ground, say the side of your arm, or hand, without knowing it. The larger surface will result in a drastically lower impedance than you are ever going to get by pinching two probe tips until your fingers are blue. If your skin is moist, say from the humidity of the air, then the impedance of your body will be even lower. If I were you, I would discontinue this practice and invest in a neon bulb tester. The AC mains are something you should respect, there are many needless deaths because of careless procedures. Andy Karanicolas MIT Microsystems Laboratory ankleand@caf.mit.edu
erk@americ.UUCP (Erick Parsons) (08/06/89)
>>From: pmb@swituc.UUCP (Pat Berry) Message-ID: <192@swituc.UUCP> >In article <427@edai.ed.ac.uk>, cam@edai.ed.ac.uk (Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550) writes: > very lightly brushing the surface. That's all just my guess. I've used > the effect for 30 years to detect live mains by touch. It works best on > shiny surfaces, stroked slowly with a very light touch. It is not a > Not recommended unless you don't mind the occasional jolt from the > mains, which probably means your skin ought to be on the dry side. I'm > talking about 250V mains, by the way. 120 is less lethal. > -- > Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550 > Department of Artificial Intelligence, Edinburgh University > 5 Forrest Hill, Edinburgh, EH1 2QL, UK >>Like they say, don't try this at home!!! What Chris does not mention is >>that it only takes 100 ma (read that one tenth of an amp) to kill you! >>At that current flow, your heart fribilates (shakes itself apart). Above >>that current flow, the heart plain stops. Why risk your life when you >>can buy a small voltmeter for under $15.00 in most hardware stores? >>Please do not ever touch a wire to see if it is hot. Such advice is not >>only dangerous, it is criminal. You risk dying on the off chance your >>skin resistance is high enough to prevent the flow of a lethal amount of >>current through your body. 120 volts will kill you just as fast as 240 >>volts. If your body presents as much as 1100 ohms of AC resistance to >>the 110 volt circuit, you will pass the lethal 100ma of current! Not to pick on you Pat as I've seen a lot of postings to this effect but give this guy a break for cryin out loud. He mentions that it is not recommended so how in the **** could this be criminal? He has been doing this for 30 YEARS!!! A lot of people these days are pretty lucky to live that long for drugs crime and alchohol. As far as getting the prescribed 100 mA through the heart, I know for a fact that there is NOT a thin wire connected from my forefinger to one edge of my heart and likewise to my other forefinger or foot or whatever part of my body decides to be ground when I get shocked. The 100 mA is going to be distributed greatly through other parts of the body (probably mostly through the skin, its the skin effect :-) I have worked around high voltages for at least 10 years and have been shocked but GOOD several times. The only shocks that have ever scared me are the ones that I couldn't get away from i.e. a loose wire that followed me as I tried to escape the evil electrons. A short shock like the one that Chris is talking about is probably to a person working around a lot of exposed LIVE connections a good thing so as to KNOW how well grounded you are at the moment. I always test hot wires with my hand if I'm fairly sure that I'm well insulated from ground. As far as testing to see if they are live by purposefully shocking myself, No *I* wouldn't do it but I am not Chris. I think that anyone working around HV live wires should get at least one jolt (110VAC) to gain a little respect for the stuff. :-( >>Come on guys, lets not kill off the readers with poorly thought out >>postings. Do you really think that people are going to run out and shock the shit out of themselves JUST because they read it here. Why don't we just stop printing newspapers if this is the case, after all these people might just go out and plant terrorist bombs in your local grocery store or start a war with a neighboring state. This is obviously an intelligant crowd here who can differiantiate between something that is potentially harmful and something that isn't. o o ^ We aren't your children !! :-) -- ------------------ // -----------Cut-Here---------------------------------- Erick Parsons // Words for the wise: *If it works don't fix it.* Sacramento Ca // mail to: ...pacbell!sactoh0!americ!erk ------------- \\// --------------------------------------------------------
johne@hpvcfs1.HP.COM (John Eaton) (08/07/89)
<<< < Does anyone know what would happen if one inadvertently, one rainy < night, with wet feet, pissed onto an electric fence? -- No and we don't want you to field test this either. I started in electronics when tubes were still around and equipment had decent voltages in them. I can still remember two of the basic saftey rules: Never touch a conductor to see if it is live. If you know a conducter is dead then first touch it with the back of your hand so if you are wrong your hand will contract away from the source rather than grabbing onto it. John Eaton !hpvcfs1!johne
weimin@aplcen.apl.jhu.edu (8361) (08/07/89)
In article <2968@mit-caf.MIT.EDU> (Andrew Karanicolas) writes: >> Well, as I promised, I tested my resistance. As I said I have dry skin. > >You are placing yourself at immense risk. You are making several >DEAD WRONG ASSUMPTIONS. [About AC/DC impedances and area of touch, etc.] Another possibly wrong assumption: the body resistance be constant under different voltages. It may be very different under 240 or 120v than under 1.5v or 9v. Weimin
morris@jade.jpl.nasa.gov (Mike Morris) (08/07/89)
...edited... In article <498@edai.ed.ac.uk> cam@edai (Chris Malcolm) writes: >I'd like to thank all those kind people who have expressed concern for >my continued existence, given my habit of touching live wires to see if >they are live. > >Well, as I promised, I tested my resistance. As I said I have dry skin. >With a light touch. such as I use for testing mains, my resistance is >>10MOhm. If I dampen my fingers by breathing on them, and grab the test >prods painfully firmly, I can bring it down to around 10KOhm. That's >still an order of magnitude under the lethal current. Unfortunately, the numbers you have are pretty useless if they were determined with a low-voltage VOM. The skin resistance varies with voltage - I discovered this with an _old_ Triplett (I think) VOM back in high school. This old meter used a 1.5v "D" cell for all but the highest scale where it used a 22.5v (or maybe 30-something v) photoflash battery. My skin resistance under 1.5v was, at times, 4 to 5 times what it was under the higher voltage. And years later when I was working a production line manufacturing CPU PC boards for General Automation we used a milliohmeter to find shorted traces - it could put out anything from 0.5 to 50v, and my skin resistance was again proven to be a crude voltage-dependent resistor. >Does anyone know what would happen if one inadvertently, one rainy >night, with wet feet, pissed onto an electric fence? The closest I can get to that is to relate a story about a stray dog... It seems that the older brother of a high school classmate of mine had a '67 Mustang with mag wheels, and a stray dog had the bad habit of urinating on the car at night. Urine is acidic and did nasty things to magnesium alloy wheels... So said gentleman parked the car on squares of aluminum door screen screen one night and wired the screens together and to one side of a neon sign transformer (15-20kv at 3-400ua), with the other side wired to the frame, and hence the wheels. He than sat down to watch out the picture window. Several hours later said stray comes up to the car, lifts his leg, and without moving a muscle jumps over 6 feet in the air - above the roof line! He comes down running, and was never seen again. Apparently the current traveled up the stream, and down his legs, causing a spasm. NO FLAMES PLEASE. The man asked a question. I was in posession of pertinent information, which I related. I am also a animal lover and do not condone that kind of behavior (in fact, I am typing this right now with a poodle- maltese mix 2-year-old sound asleep in my lap). Mike Morris UUCP: Morris@Jade.JPL.NASA.gov #Include quote.cute.standard | The opinions above probably do not even come cat flames.all > /dev/null | close to those of my employer(s), if any.
preacher@clmqt.marquette.Mi.US (J.A. Fegan) (08/08/89)
> <<< > < Does anyone know what would happen if one inadvertently, one rainy > < night, with wet feet, pissed onto an electric fence? > -- well I many many moons ago back when my dad and his brother were but young tikes and living on a dairy farm, on a hot day in august my uncle did just that. the way the story goes is that he was late for supper as he had to walk back so far after his run in to who knows were. this is not something that i would every wish to experience not ever... 1 -= p.w. fuzzface =- 0 -- Never be backward wen visitors kum; | mailrus!sharkey!lopez!preacher Don't sit there quiet like a sap |-------------------------------- Be sociable! Tell'em wot momma called pa When she found the maid parked on his lap. -- Tha Return Uv Snowshoe Al
heumann@hpmtlx.HP.COM ($John_Heumann@hpmtljh) (08/08/89)
> 120 and 220 ARE both *potentially* (no pun intended) lethal, but you're more > likely to get into trouble with 220 - as it can force a deadly current through > a higher-impedance load, meaning that you don't have to be in *quite* as good > contact as you would need to check out for good on 120. I = E/R, so any time > you set up a situation where you can get 100 mA through the heart, well, > please smile and leave a happy-looking corpse. I believe your presumption that all currents above a threshold are lethal is incorrect. What I recall is that currents within a fairly narrow range induce ventricular fibrillation and are potentially lethal. Once you exceed this range, higher currents are actually LESS dangerous since they cause simple tetany rather than fibrillation. (Of course if you go to really high currents you can literally fry, but now were talking about lots of kilovolts). I'd agree that 220/240 if generally more dangerous given typical skin resistance but 120 should still be treated with respect. I've even heard of accidental fatalities from 10-20V supplies when a low resistance contact was accidentally made. -jh-
wbrown@beva.bev.lbl.gov (Bill Brown) (08/08/89)
In article <498@edai.ed.ac.uk> cam@edai (Chris Malcolm) writes: >I'd like to thank all those kind people who have expressed concern for >my continued existence, given my habit of touching live wires to see if >they are live. > ... >Well, as I promised, I tested my resistance. As I said I have dry skin. >With a light touch. such as I use for testing mains, my resistance is >>10MOhm. If I dampen my fingers by breathing on them, and grab the test >prods painfully firmly, I can bring it down to around 10KOhm. That's >still an order of magnitude under the lethal current. So you all kind >folks can stop worrying about me! > As best I can remember, (it was a long time ago - longer than I like to contemplate!!!) CG-165 , "U.S.Coast Guard Electronics Manual", quoted 50 ma as being enough to stop the heart, or in the case of A.C. (60 Hz) put it into fribulation(sp?). Aw what the heck, 1/2 order of magnitude is plenty! Like gee whiz, a factor of two ought to be ok! Especially since al theses values are so exact. An inch is as good as a mile! I vaguely recall a line from something called "The 10 Electro-Commandments" that went something like this: "Tary not among those fools who engage in intentional shocks, as they are surely unbeleivers and are not long for this world." There was also a line to the effect that: "... electric cooking is a slothful process and one may simmer in ones' juices for hours before the Maker sees fit to drag thee from this vale of tears." >Does anyone know what would happen if one inadvertently, one rainy >night, with wet feet, pissed onto an electric fence? >-- The exercise is left to the foolish as an experiment. >Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550 >Department of Artificial Intelligence, Edinburgh University ^^^^^^^^^^^^^^^^^^^^^^^ AHA!!!!!! >5 Forrest Hill, Edinburgh, EH1 2QL, UK -bill wlbrown@lbl.gov Disclaimer: These opinions are my own and have nothing to do with the official policy or management of L.B.L, who probably couldn't care less about employees who play with trains.
rodman@mfci.UUCP (Paul Rodman) (08/08/89)
> >If I were you, I would discontinue this practice and invest in a neon bulb >tester. The AC mains are something you should respect, there are many >needless deaths because of careless procedures. > And if you can spring for more money another nice tool is the "click box". A "geiger counter" for live wires. This little bugger will tell you if wires are live via their electric field, without any connection required. Very useful for those occasions when you have 20 Romex wires coming into an attic, say, and you want to know which one is your wire of interest. Just have somebody flip the breaker on and off and sniff for for the wire that clicks/doesn't click. Or you stick a light on the wire which is turned on and off at 1hz, and you sniff for that. Neon bulb a lot cheaper, tho. pkr
myers@hpfcdj.HP.COM (Bob Myers) (08/09/89)
>>contact as you would need to check out for good on 120. I = E/R, so any time >>you set up a situation where you can get 100 mA through the heart, well, >>please smile and leave a happy-looking corpse. >I believe your presumption that all currents above a threshold are lethal >is incorrect. What I recall is that currents within a fairly narrow >range induce ventricular fibrillation and are potentially lethal. Once you >exceed this range, higher currents are actually LESS dangerous since they Technically you are, of course, correct - but are you willing to bet your life on the hope that the current will exceed the upper end of that range? Bob Myers KC0EW HP Graphics Tech. Div.| Opinions expressed here are not Ft. Collins, Colorado | those of my employer or any other myers%hpfcla@hplabs.hp.com | sentient life-form on this planet.
bph@buengc.BU.EDU (Blair P. Houghton) (08/09/89)
In article <17660006@hpfcdj.HP.COM> myers@hpfcdj.HP.COM (Bob Myers) writes: > >> It doesn't matter wether it's 120 or 220, They're both >> lethal. It's not the volts that kill, it's the amps. > >Y'know, that last is said often enough that people are starting to repeat >it as Holy Writ without actually understanding it. Major power companies repair high-tension (quarter-million-volt) lines in remote areas by sending cable dogs up in helicopters to work on the live wires barehanded. It ain't the volts that kill, it's the amps. --Blair "Or, in my case, it's the vertigo..."
dplatt@coherent.com (Dave Platt) (08/09/89)
In article <880007@hpmtlx.HP.COM> heumann@hpmtlx.HP.COM (John Heumann) writes: > I believe your presumption that all currents above a threshold are lethal > is incorrect. What I recall is that currents within a fairly narrow > range induce ventricular fibrillation and are potentially lethal. Once you > exceed this range, higher currents are actually LESS dangerous since they > cause simple tetany rather than fibrillation. (Of course if you go to really > high currents you can literally fry, but now were talking about lots of > kilovolts). There's another factor involved: timing. The heart's response to a pulse of current will depend to some degree on the point in the heartbeat-cycle at which the pulse occurs. There's a very interesting writeup on this phenomenon in a book on biological rhythms published by The Scientific American Library. Briefly: the heart's internal "pacemaker" can be modelled as an oscillator, with electrical charges travelling around the heart-muscle in a recirculating pattern. A strong electrical shock (strength >> a threshold) will typically reset the "phase" of this oscillator to a specific value, regardless of the phase of the oscillator prior to the shock. That is... if you apply a strong shock to the heart, it will beat immediately, with the next beat following at the usual interval. A weak electrical shock (strength << threshold) will not reset the phase of the clock to its starting point... instead, it will simply shift the phase of the clock by a lesser or greater amount (it'll shorten or lengthen the interval to the next heartbeat, without triggering a beat immediately). If you draw up a three-dimensional graph (X = starting phase, Y = current applied, Z = resulting phase), you'll find that there is an inescapable singularity in the Z-axis values... this is a topological necessity. In effect, for one certain X (starting phase) and one certain Y (current), the resulting phase is indeterminate. This phenomenon exists in many sort of perturbable phase oscillators (circadian rhythms, etc.). Different systems display the singularity in different ways. In some systems, the singularity is a repelling point... the system "slides" back into stable behavior at some unpredictable point in its cycle. In other systems, the singularity is an attracting point... the oscillator "hangs up" and begins exhibiting nonregular behavior. The heartbeat-cycle is of the latter sort; if the oscillator is disrupted, the heart fibrillates. Tests on animals have shown that this singularity isn't simply a mathematical artifact... it really exists. At one specific point in the heartbeat cycle, a properly-measured pulse of current will very probably throw the heart into fibrillation. The _same_ pulse, at a different time in the heartbeat cycle, does not cause fibrillation; a stronger or weaker pulse does not cause fibrillation. Once the heart starts fibrillating, it will not tend to regularize itself; someone must apply a pulse of current (>> threshold) in order to kick the oscillator out of its unstable mode and back into a regular phased operation. So, it seems that your chances of surviving a shock depend not only on the strength of the shock, but also on the timing of the shock itself. The fact that you've been "bitten" by a wild voltage, and survived, does NOT mean that the same voltage/current could not kill you the next time. Don't do this at home, kids. Disclaimer: I've probably gotten some of the details wrong, as it has been a couple of years since I read about the phenomenon. -- Dave Platt FIDONET: Dave Platt on 1:204/444 VOICE: (415) 493-8805 UUCP: ...!{ames,sun,uunet}!coherent!dplatt DOMAIN: dplatt@coherent.com INTERNET: coherent!dplatt@ames.arpa, ...@uunet.uu.net USNAIL: Coherent Thought Inc. 3350 West Bayshore #205 Palo Alto CA 94303
erk@americ.UUCP (Erick Parsons) (08/09/89)
>From: wbrown@beva.bev.lbl.gov (Bill Brown) Message-ID: <3517@helios.ee.lbl.gov> >>Does anyone know what would happen if one inadvertently, one rainy >>night, with wet feet, pissed onto an electric fence? >>-- >The exercise is left to the foolish as an experiment. I remember with a certain amount of (sick) humor being a boy in the scouts and happening across an electric fence with a group of similiar aged boys. The Eagle scout amongst us rookies decided that HE would like to know what would happen if his spit hit the dangerous thing. I suppose that he was expecting some kind of fireworks show but instead the spit never disengaged from his lips (considered a drool) and the poor Bast*rd got hit right smak dab in the lips (OUCH!!! :-{ ). The ensuing lurch was a dead giveaway as to his ultimate fate though he said nothing (we did- %-} ). -- ------------------ // -----------Cut-Here---------------------------------- Erick Parsons // Words for the wise: *If it works don't fix it.* Sacramento Ca // mail to: ...pacbell!sactoh0!americ!erk ------------- \\// --------------------------------------------------------
erk@americ.UUCP (Erick Parsons) (08/09/89)
>From: malcolm@Apple.COM (Malcolm Slaney) Message-ID: <33854@apple.Apple.COM> > Malcolm >P.S. I decided to stick to computers after watching Commonwealth Edison >check to see if a 10-50 kV line was live in the rain by laying a wooden >stick across it and seeing if it sparked. This was called fuzzing the >line. Not my idea of a fun time. Me Too !! Recently here in Sacramento we had some unusual lightning activity. Read.. 1 and a half days of straight lightning (California in the summertime) The local Electric company SMUD lost 300 pots (Line X-formers) in one night. These poor suckers got a LOT of overtime replacing x-formers WHILE the storm was still in full force. Talking to one of the linesman revealed that this money game was a game of Chance as replacing x-formers during an electrical storm Can be a shocking experiance (He called it Blood Money). 7 locals were hit by lightning and a bunch of fires. YOUCH !! For those of you from other localls it NEVER rains in Ca. in the summertime let alone thunders. -- ------------------ // -----------Cut-Here---------------------------------- Erick Parsons // Words for the wise: *If it works don't fix it.* Sacramento Ca // mail to: ...pacbell!sactoh0!americ!erk ------------- \\// --------------------------------------------------------
jimc@iscuva.ISCS.COM (Jim Cathey) (08/09/89)
In article <3517@helios.ee.lbl.gov> wlbrown@lbl.gov (Bill Brown) writes: >>Does anyone know what would happen if one inadvertently, one rainy >>night, with wet feet, pissed onto an electric fence? >The exercise is left to the foolish as an experiment. ^^^^^^^ Or the gullible! I had a friend in grade school whose uncle talked him into just that action. They both ended up on the ground -- the uncle from laughing and my friend because he couldn't stand up anymore. (I don't think it was raining, or nighttime.) Friend said it was worse than getting kicked in the nuts. Needless to say I didn't rush right home to see if he was right! +----------------+ ! II CCCCCC ! Jim Cathey ! II SSSSCC ! ISC-Bunker Ramo ! II CC ! TAF-C8; Spokane, WA 99220 ! IISSSS CC ! UUCP: uunet!iscuva!jimc (jimc@iscuva.iscs.com) ! II CCCCCC ! (509) 927-5757 +----------------+ "With excitement like this, who is needing enemas?"
malcolm@Apple.COM (Malcolm Slaney) (08/09/89)
In article <3663@buengc.BU.EDU> bph@buengc.bu.edu (Blair P. Houghton) writes: >Major power companies repair high-tension (quarter-million-volt) lines >in remote areas by sending cable dogs up in helicopters to work on the >live wires barehanded. > >It ain't the volts that kill, it's the amps. Just so nobody gets the wrong impression......working on live transmission lines is an example of "doing what the birds do" and not an example of high voltage and thus low amps is safe. There is a long article on this practice in a recent issue of IEEE Spectrum. It is not a universally accepted practice since one mistake is pretty fatal. The basic principle is to work from a helicopter or an insulated cherry picker. As long as there is no electrical path to ground everything is going to be fine. These workers usually wear a conductive suit to keep the electric fields constant everywhere and are physically strapped to the cable so that they are always at the line voltage. Malcolm P.S. I decided to stick to computers after watching Commonwealth Edison check to see if a 10-50 kV line was live in the rain by laying a wooden stick across it and seeing if it sparked. This was called fuzzing the line. Not my idea of a fun time.
henry@utzoo.uucp (Henry Spencer) (08/10/89)
In article <31069@coherent.com> dplatt@coherent.com (Dave Platt) writes: >There's a very interesting writeup on this phenomenon in a book on >biological rhythms published by The Scientific American Library... >If you draw up a three-dimensional graph (X = starting phase, Y = >current applied, Z = resulting phase), you'll find that there is an >inescapable singularity in the Z-axis values... the singularity is >an attracting point... the oscillator "hangs up" and begins exhibiting >nonregular behavior... I saw what was probably the same writeup when it was originally published in Scientific American (the S.A. books are usually just collections of articles). They had a 3D graph of the heart oscillator's behavior, using color as the third dimension, which I remember vividly because of a friend's comment. The graph was a swirl of bright colors, with the singularity showing as two oval black spots side-by-side in the middle. My friend saw it, read the caption, and commented: "the eyes of Death". Best not to mess with those milliamps... -- 1961-1969: 8 years of Apollo. | Henry Spencer at U of Toronto Zoology 1969-1989: 20 years of nothing.| uunet!attcan!utzoo!henry henry@zoo.toronto.edu
henry@utzoo.uucp (Henry Spencer) (08/10/89)
In article <31069@coherent.com> dplatt@coherent.com (Dave Platt) writes: >... Once the heart starts >fibrillating, it will not tend to regularize itself; someone must apply >a pulse of current (>> threshold) in order to kick the oscillator out of >its unstable mode and back into a regular phased operation... Something I've occasionally wondered about: granted that practically nothing but a strong shock will get the oscillator functioning properly again, would CPR mechanically override the fibrillating heart muscle and keep blood flowing? -- 1961-1969: 8 years of Apollo. | Henry Spencer at U of Toronto Zoology 1969-1989: 20 years of nothing.| uunet!attcan!utzoo!henry henry@zoo.toronto.edu
myers@hpfcdj.HP.COM (Bob Myers) (08/10/89)
>>> It doesn't matter wether it's 120 or 220, They're both >>> lethal. It's not the volts that kill, it's the amps. >> >>Y'know, that last is said often enough that people are starting to repeat >>it as Holy Writ without actually understanding it. >Major power companies repair high-tension (quarter-million-volt) lines >in remote areas by sending cable dogs up in helicopters to work on the >live wires barehanded. >It ain't the volts that kill, it's the amps. > --Blair > "Or, in my case, it's the vertigo..." Blair, did you actually READ my entire posting? Bob M.
ferguson@maitai.SRC.Honeywell.COM (Dennis Ferguson) (08/10/89)
In article <17660006@hpfcdj.HP.COM> myers@hpfcdj.HP.COM (Bob Myers) writes: > >> It doesn't matter wether it's 120 or 220, They're both >> lethal. It's not the volts that kill, it's the amps. > > >Y'know, that last is said often enough that people are starting to repeat >it as Holy Writ without actually understanding it. Yes, it is the amount >of current passing through the body (particularly the heart itself) which >determines whether or not you'll just get a tingle, or wind up as a customer >of the local coroner.... Actually, the problem with 220 and 120v is partially the 60Hz. Most electrocution deaths are the result of fibrillation of the heart. The 60Hz current wrecks the timing to the heart... resulting in spasms that prevent pumping action. The tissue itself is undamaged. Fibrillation can also occur as a result of other circumstances and has been induced in heart patients with very low currents (microamps). The classic recovery procedure is to use a dibrillator which applies a *high* voltage charge across the heart, clearing the spasms and restarting the heart. I once worked for a power company as a communications engineer and we had a technician go into a substation to read the serial numbers off a capacitor bank. He bent down to read the numbers and lost his balance, falling backwards onto the capacitors. The capacitors, charged to 7500 volts, discharged through his body (the capacitors were across a distribution line for power factor correction). He lived. Dennis
cam@edai.ed.ac.uk (Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550) (08/10/89)
In article <2968@mit-caf.MIT.EDU> ankleand@mit-caf.UUCP (Andrew Karanicolas) writes: > I wrote: >>Well, as I promised, I tested my resistance [etc.] ... >You are placing yourself at immense risk. You are making several >DEAD WRONG ASSUMPTIONS. You measured your resistance but thats only >part of the story. You really need to measure the IMPEDANCE of your > [lots more useful advice] >If I were you, I would discontinue this practice and invest in a neon bulb >tester. The AC mains are something you should respect, there are many >needless deaths because of careless procedures. I can't stand it any longer! There is no alternative: I shall simply have to tell the truth. Ever since I got a shock from the live mains THROUGH a mains neon tester while standing with one foot in the toilet bowl (it IS the smallest room), I have relied on a battery powered remote mains tester, which detects mains AC fields through an inch or so of sundry insulation, locates dead fuses without even taking the cover off the fuse-box, detects live CRTs and electrostatically charged cats at several paces, etc.. Did I mention the heroic electricians of my AC/DC boyhood, who would ask my mother "You got AC or DC here Mum?", to which she would reply "I don't know!", whereupon they would extract a light bulb, switch on the lamp, plunge a thumb into the socket, and announce, "It's AC, Mum". I expect they're all dead now, of course ... -- Chris Malcolm cam@uk.ac.ed.edai 031 667 1011 x2550 Department of Artificial Intelligence, Edinburgh University 5 Forrest Hill, Edinburgh, EH1 2QL, UK
andrew@kean.mun.ca (08/10/89)
In article <31069@coherent.com>, dplatt@coherent.com (Dave Platt) writes: > If you draw up a three-dimensional graph (X = starting phase, Y = > current applied, Z = resulting phase), you'll find that there is an > inescapable singularity in the Z-axis values... this is a topological > necessity. In effect, for one certain X (starting phase) and one > certain Y (current), the resulting phase is indeterminate. > > This phenomenon exists in many sort of perturbable phase oscillators > (circadian rhythms, etc.). Different systems display the singularity in > different ways. In some systems, the singularity is a repelling > point... the system "slides" back into stable behavior at some > unpredictable point in its cycle. In other systems, the singularity is > an attracting point... the oscillator "hangs up" and begins exhibiting > nonregular behavior. The heartbeat-cycle is of the latter sort; if the > oscillator is disrupted, the heart fibrillates. Of course. 'Tis Chaos (or Nonlinear Dynamics for you stickywigs). I remember reading that one of the first uses of chaos research in biology was to make mosquitos insomniac by using flashes of light to turn their internal sleep/wake clocks into chaotic behavior. -Andrew.
larry@kitty.UUCP (Larry Lippman) (08/11/89)
In article <1989Aug9.175048.21910@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes: > >... Once the heart starts > >fibrillating, it will not tend to regularize itself; someone must apply > >a pulse of current (>> threshold) in order to kick the oscillator out of > >its unstable mode and back into a regular phased operation... In some cases of ventricular fibrillation, a sharp physical blow to the mid-sternum ("precordial thump") will arrest ventricular fibrillation - provided that the physical blow is administered within 60 seconds of the onset of fibrillation. > Something I've occasionally wondered about: granted that practically > nothing but a strong shock will get the oscillator functioning properly > again, would CPR mechanically override the fibrillating heart muscle and > keep blood flowing? Properly administered CPR will indeed maintain some level of cardiac circulation even in the presence of ventricular fibrillation. <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> TEL 716/688-1231 | 716/773-1700 {hplabs|utzoo|uunet}!/ \uniquex!larry <> FAX 716/741-9635 | 716/773-2488 "Have you hugged your cat today?"
hughes@math.berkeley.edu (Eric Hughes) (08/12/89)
As long as we're telling stories about electric fences, I once had a farmer show me how he tested his electric fence. He took a long piece of green grass, held one end between thumb and forefinger, and touched the other end to the fence wire. Without about eight inches of plant material between your hand and the fence, all you feel is a little thump when the pulse comes through. He even did an impromptu demonstration of Ohm's Law, by showing us how the thump got stronger if you put less grass in the conduction path. :-) Eric Hughes hughes@math.berkeley.edu ucbvax!math!hughes
bph@buengc.BU.EDU (Blair P. Houghton) (08/13/89)
In article <17660013@hpfcdj.HP.COM> myers@hpfcdj.HP.COM (Bob Myers) writes: >>>> It's not the volts that kill, it's the amps. >>> >>>Y'know, that last is said often enough that people are starting to repeat >>>it as Holy Writ without actually understanding it. >> >>Major power companies repair high-tension (quarter-million-volt) lines >>in remote areas by sending cable dogs up in helicopters to work on the >>live wires barehanded. >> >>It ain't the volts that kill, it's the amps. >> >> "Or, in my case, it's the vertigo..." > >Blair, did you actually READ my entire posting? I'll ignore that. --Blair "It ain't the responses that kill, it's the flames."