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Re: Measuring inside a coil
>> Greg or someone was inside the secondary terminal not the
>> secondary coil.
>> With a large TC the magnetic fields could be very high so
>> don't wear your wrist watch.
>> -JHC
>While I donīt want to volunteer (and I wouldnīt fit inside
>my coil or toroid anyway :o)), I think as soon as you bring
>any kind of conductor inside a Faraday cage, all safety bets
>are off. I think you would nullify the effect of the cage. IF the
>cage is connected to ground, you should still be safe from
>outside strikes, but if any of the measurement cables that
>go inside the cage get hit, (I think) there would effectively
>be no cage present. Of course, you MIGHT be lucky and
>not get any strikes to the measuring cables INSIDE of a
>secondary, but I would be tooooo chicken to try. (:o)
>
>While I am sure that someone will point out the flaw,
>question: Wouldnīt the secondary itself be a sort
>of Faraday cage for someone standing inside? While
>I have seen interturn arcs, etc, I have never seen a
>coil arcing inside (from one side of the former to
>the other). Saying this, I am assuming NO conductors
>enter inside the secondary coil former, of course.
>
>Coiler greets from germany,
>Reinhard
The B field inside the electrode on Electrum appeared to
be negligible, at least when measured by forming a 6" loop
with the scope electrodes. The scope would scarcely even
trigger on this event. The Sony Mavica digital camera also
operated perfectly in the sphere, its 3.5" floppy disk did
not incur any data corruption.
The E field was more prominent -- with the scope probes
open circuit, a peak voltage of about 8-9v was measured.
Not surprising, given that the cage was made of SS 304,
and every item in the hostile universe outside was
jiggling around at almost 2,ooo,ooo volts!
During the dart leader msmt tests, one CT was located
down in the secondary structure about a foot, and its
signal wire ran up into the sphere, to the scope. No
noticable problems with induced voltages were encountered.
True, a wire entering the sphere cage would breach its
electrical integrity, but probably not in a fatal way.
After all, such a wire could not launch an arc into the
sphere any further than its insulation can support between
the wire and breach in the sphere wall. The etiquette for
handling such an invader would be the same as for a wire
hanging out of your laboratory wall, with 100kV of RF on it.
The secondary would not classify as a Faraday cage IMO;
At least, I would not seek shelter inside a cylinder with
a vertical gradient of 10kV/inch!! The electric field on
the inside of the secondary is more uniform than on the
outside, and is higher at the base, where the induced
volts/turn are greater, sometimes even challenging the
surface flashover strength of the inside coilform.
--
-GL
www.lod-dot-org