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August 10th 03, 08:51 PM
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In article , Gary S.
Idontwantspam@net writes: On Sun, 10 Aug 2003 13:06:23 +0100, Paul Burridge wrote: On 10 Aug 2003 03:22:06 GMT, (Avery Fineman) wrote: I really don't know the medical-biological low threashold for direct cardiac stimulation through an opening in the chest cavity. I don't care to know. I care to know NOT to futz around with my or anyone else's body with anything above the "30-30" limits. As a general safety rule I'm sure you're right. However it does overlook the fact that different individuals have different tolerance levels, hence the fatality at 12V (the only recorded one, I believe) and that Polish electrician who checks for the presence of 230VAC by It also matters what the surface resistance of your skin is, and how good a "connection" to the nervous system and heart. For example, You could put dry fingers on a 9V battery and not feel a thing, but if you lick your fingers first, get a real tingle. Same voltage, but the moisture allows current to flow. Too bad the old "B" batteries aren't common any more. As a 15 year old (back in the prehistory of mankind) newcomer hobbyist to radio and electronics, I couldn't feel anything across the snap-on terminals of a 67 V "B" battery. Curious, I touched my tongue to them. Z A P ! ! ! ! Stunned, I waited about a half hour to get my tongue unrolled. Never EVER tried such a totally dumb idea again... In medicine, the defibrillator paddles are covered with a conductive gel, and use a precise pulse of voltage and current. In open heart procedures, lower voltage and current is used, with paddles applied directly to the heart. True enough. What is overlooked is that medical instruments, meters, appliances are all precisely calibrated-adjusted-designed- to-be-stable-in-their-settings...based on KNOWN INFORMATION to medical and biological people. Of course, disrupting the heart rhythm may happen with lower voltage, especially AC or RF. Why is being careful such a problem for some? Bravado and a general feeling of immortality. Especially true for males and once useful as a survival thing way back in time. Some actually believe their boast "It can't happen to ME!" :-( No problem for the morticians...keeps their business going. The solid-state era was born with a dangerous side-effect: Low supply voltages. High voltages of 100 to 300 VDC weren't needed with transistors. Most folks are not able to feel supply voltages under 15 V, DC or AC. As a result they get way too CASUAL about handling supply rails with the power on. "Familiarity breeds contempt," etc. When they take that casual attitude towards handling mains supplies with 115 to 230 VAC input, there's trouble just waiting to happen. It's like sticking one's hand into a snake basket...the snake may bite or it may not, depends on the snake...if it bites the bite can be deadly. Len Anderson retired and still living in the current reality after 56 years in electric things |
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