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Re: RF biological hazards? (fwd)
---------- Forwarded message ----------
Date: Fri, 1 May 1998 20:42:00 -0500
From: "Robert W. Stephens" <rwstephens-at-headwaters-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: RF biological hazards? (fwd)
> Date: Wed, 29 Apr 1998 15:30:48 -0600 (MDT)
> To: tesla-at-pupman-dot-com
> Subject: RF biological hazards? (fwd)
> From: Tesla List <tesla-at-pupman-dot-com>
>
>
> ---------- Forwarded message ----------
> Date: Wed, 29 Apr 1998 22:01:21 +0100
> From: R M Craven <craven-at-globalnet.co.uk>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: RF biological hazards?
>
> Perhaps this subject has already been covered: I imaginr Mark Rzez.
> would be able to answer with ease.
>
> I was reading a IEEE conference proceeding recently, which showed
> that "skin depth" in people was several tens of cm at a few MHz,
> decreasing with frequency. I haven't got the reference to hand but if
> anybody wants me to find it, I'll do so.
>
> Basically, RF currents do not flow over the outer mm of human skin:
> they reach significant penetration depths, according to this respected
> publication. I believe the depth was quoted based on 1/e density.
>
> So, the fact that TC discharges at a few hundred kHz are painless is
> NOT an indicator that they are sfae. RMS heating will still occur,
> won't it? And that might be deep inside your body. The fact that we
> feel little is perhaps more related to nervous response times as was
> recently discussed.
>
> Can anyone raise any comments on this?
>
> Richard Craven, Malvern, England
Richard, All,
I'm very glad that you brought this topic up. I was never
comfortable with the *skin effect* formula designed for metallic
conductors being used to explain electrical current behaviour on less conductive
human tissue and bone.
Can you reference the IEEE papers on this so I may look them up
please?
I frequently hold a metal bar into the 22 inch discharge off my 833A
driven vac-toob magnifier TC to show off to visitors. I feel absolutely no
sensation in my hand whatsoever during the event, but afterwards my hand is
slightly sore to the bone, as though it had been battered by a meat tenderizing
hammer. This TC produces nearly a kW in output power at perhaps 1/2 MHz
(I've never bothered to measure the exact frequency of Fo).
Each recurring RF burst envelope is sinusoidal and only 50% duty cycle, being
energized during positive going mains cycles only, leading to a rep
rate of 60 Hz. In this fashion, my hand is being hammered at 60
times per second, but the voltage rise is a nearly perfect sine, so
as for voltage rise waveform, it is being battered slightly *gently*.
I don't know if my physiological effects come from hammering of the
nervous system at 60 Hz or from RF heating of deep tissue and muscle,
or perhaps of nerves themselves.
I'd be very interested in any comments, experiences or stories that
anyone else might wish to share on this topic.
Robert W. Stephens
Director
Lindsay Scientific Co.
RR1 Shelburne, ON Canada L0N-1S5
Tel: 1-519-925-1771 Fax:
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