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Re: Corum's new paper



Hi Bill,

At 04:58 PM 04/12/2000 +0000, you wrote:
snip...

>Number four.  For all those disagreeing with the Corum's findings 
>of their article on my web site, please ask yourselves this:  Did
>you (accurately and faithfully) perform their Test # 2?  What were
>*YOUR* results????? 
>
>Best regards,
>Bill Wysock.
>

snip...

Ok!  Here are MY results following the five steps of the paper's "Test II".

My primary is 4.25 inches in dia.
1180 turns #24 wire that is 26.125 inches long.

The toroid is John's Freau's 13 inch outer diameter with a 4 inch diameter
section.  The center of the toroid sits 31 inches off my wood floor that is
about 4 inches above the dirt underneath (old house).


"Step 1. With the sphere (or toroid) attached on the top of your coil and a
ground connected to its base, link couple a signal generator into the
bottom of the coil and hold up an oscilloscope probe in the vicinity of the
sphere - but not so close as to interfere with the experiment. Sweep the
signal generator until the first Vmax is observed. Call this the system
resonant frequency, Fo."


I had to add a 12 inch section of wire to the end of the probe to act as a
little antenna.  I measured 247.3 kHz.


"Step 2. With the coil disconnected, but the top capacitor supported at the
same height above ground as when it's on the coil, measure C."


This isn't easy! ;-)  There needs to be a connection to the toroid that
will affect the measurement, but this is how I did it.  I connected a wire
to the toroid and ran it down to the LCR meter.  I took the first
measurement.  I then cut the wire at the torroid to give me a second
measurement and I assume the difference is the toroid's capacitance.  I got
13.3pF.

According to a capacitance formula for a toroid (Bert Pool), I get 14.45pF
So I am probably close...


"Step 3. Calculate the capacitive reactance of the top capacitor at the
measured system resonant frequency fo: XC(fo) = 1/(2piFoC)."


Using the 13.3 pF number, I get 48389 ohms reactive.


"Step 4. With L and C still disconnected, measure the self inductance of
the coil (without the top capacitor) with an LCR bridge at 1 kHz (i.e., at
a frequency so low that the current on the coil will be uniformly
distributed). Call this value L."


The 1kHz LCR meter gives 22.1mH.


"Step 5. Calculate the frequency at which the lumped-element inductance has
the same reactance as the actual capacitive reactance in steps 1 and 3.
That is, f = XC(fo)/(2piL). If f ~ fo then the coil in step 1 was operating
in the lumped-element regime."


The frequency is 348.5kHZ...  I guess I am not convinced...


I think two critical errors were made in this test:

First, the self capacitance of the coil is not taken into account!  The
bare secondary coil has an Fo frequency of 351.5 kHz.  That implies a self
capacitance of 9.28pF.  This is obviously a darn big capacitance to not
take into account!!  If I simply add this forgotten capacitance to my
13.3pF terminal, I get a frequency of 262.9kHz which is much closer to the
real Fo frequency of 247.3 kHz.  In this case, it is only 6.3 percent off
which almost hits the paper's 5% number.  Even Tesla's notes take the self
capacitance (he refers to it as the distributed capacity) into account.
There is no reason why this paper, written almost 100 years later, would
not address this critical,very well known, and well understood parameter.

Second, The terminal capacitance and the coil's self capacitances add
together due to their physical structure in space.  They mix together in a
complex way that one cannot easily calculate.  Thus E-Tesla5 can be used to
find their combined capacitance.  In my case, E-Tesla5.1 gives a combined
system capacitance of 20.3 pF for a total system resonance frequency of
237.8 kHz.  That is 3.8 percent off which is pretty good considering the
coil is in a complex room with lots of close by metal objects and I used
accuracy level three because I am in a hurry.  If I were careful to set it
up in a more "ideal" room and use the full accuracy, I could get much closer.

On page 7 they do an example with "the coil in photo 1".  I calculate the
self capacitance of that coil as being 33.2 pF (Medhurst's formula of self
capacitance).  when I add this to the 25.6pF they got for the terminal, I
get a calculated "lumped" value of the resonant frequency of 140.0kHz.
That is 3.65 percent off!!!  Perhaps that could be called a "Great triumph
of the lumped element theory when done right!!" (GTOTLETWDR ;-))

So I have "accurately and faithfully" performed Test # 2.  I have
"correctly" applied the lumped parameter models and they seem to work just
fine (better than I expected!).

I must admit, I am now even far less impressed with the paper's claims...

Cheers,

	Terry