Re: Re: [TCML] Tesla Coil Output Hazards, Skin Effect?

[Chip Atkinson <chip@xxxxxxxxxx>]

Hi Jim.

If you have references, that would be great to put into the tesla coil
safety sheet.  I keep seeing over and over again things like "Tesla did
it", "just hold a metal object in your hand", etc. 

Thanks in advance.

Chip

On Fri, 23 Nov 2007, Jim Lux wrote:

> 
> 
> -----Original Message-----
> >From: Peter Richards <pete.richards@xxxxxxxxxxxxxxx>
> >Sent: Nov 22, 2007 6:54 PM
> >To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> >Subject: Re: Re: [TCML] Tesla Coil Output Hazards, Skin Effect?
> >
> >
> >Elitism and arrogance dont help advance knowledge.
> >
> >Tesla demonstrated passing HV HF through his body many times. At times the currents were sufficient to melt copper bar only a short distance from his hands. Having read the lecture notes written when he did this, the power levels here were over 10kVA. I take it Tesla wouldn't qualify as a 'real engineer' by this measure then? 
> 
> That's the classic "anecdotal" story: "A did it and survived with no *apparent* ill effects, so it must be safe for B, C, and D to do it".  Nonsense.
> 
> Fallacies:
> a) You do not know the exact configuration of what was done.
> b) You do not know that no ill effects occurred, either chronic or acute, when reading a promotional account (David Copperfield has commented numerous times that the reason people think that something he does is impossible is that it hurts to do it, and they don't think he's willing to take the pain)
> c) You don't know what the vulnerabilities are in all cases for all people. Perhaps the folks who aren't apparently injured are physiologically more resistant.
> d) Maybe the damage is a low probability effect.  If it only occurs 1 in 1000 events, and you repeated the stunt 10 times, you're unlikely to see the ill effect. (This is the "I climb my 100 ft antenna tower with no safety gear and haven't died, so clearly the gear's not needed" fallacy)
> 
> 
> 
> 
> 
> 
> >You would enjoy reading "Biological Effects of External Ionising Radiation". I'll get the ISBN for you if required. There are many such books. The human body merely acts as a large capacity added to the terminal. As part of the circuit rather than a target for external influence, there is a far lesser case for concern. 
> 
> 
> 
> a) The hazards from Tesla coils are not from *ionizing* radiation, so your book isn't of much use.
> b) There is certainly current flowing through your body in one of these stunts, and the understanding of the effects of that current is not all that great.  Where densities are high enough, there are the usual burn issues, but there are a number of insidious effects that I wonder if you've thought through.  For instance, you could have large area low current density at the surface, which concentrates in high conductivity tissues.  Perhaps you might want to read the data from the air force on the ankle and wrist pain from relatively low RF exposure.  I can find the reference if you're interested.
> >
> >When properly configured, there is no low frequency component whatever in the coil output. There is no physical sensation of anything - not pin-pricks, heat - nothing.
> 
> This is because the signal is at a frequency well above the "low pass cutoff" of your nerves. All you might feel is the thermal effects, and because they are deep, and your body puts all the heat sensing nerves on the surface, you won't feel anything.  There are a fair number of documented cases in the RF safety literature of people have reported RF burns that were painless when they occurred, even with significant tissue damage (as in 3rd degree burns).
> 
> 
> 
> 
> > No side effects have been noticed by myself running power levels to 5kVA input. I have done this countless times over the last 28 years. 
> 
> This is the classic "anecdote" fallacy.  One test case without rigorous controls and experimental method does not form a good basis for safety policies. (Unless you've had periodic neurological and physical workups over those 30 odd years, and have an identical twin brother who's done the same and didn't get exposed to the coil).
> 
> Practically speaking, how would know if there were long term side effects?  Maybe your hair turns grey (or falls out) 6 months earlier? (I don't actually think this is a risk, by the way. it's just an example)
> 
> 
> 
> >I would personally be more concerned with 'point to (metal) plate' type discharges. These can be sufficiently energetic to knock X-Rays out of the plate in large amounts. Doses here are cumulative. 
> 
> In air, it's pretty unlikely to generate X-rays.  You'd have to have di/dt many, many orders of magnitude greater than seen in tesla coils.  UV exposure is a bigger hazard.
> 
> 
> 
> 
> >Having said all that, if it scares you - why would you do it? 
> >
> >When one is sufficiently familiar with their apparatus to be SURE of what the circuit is doing - and can be supremely confident in the shaping of the electrostatic stresses around the coil such that a secondary arc to the primary coil NEVER occurs, then - the decision rests with the individual.
> 
> 
> 
> As always, the individual gets to decide. 
> 
> 
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