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Using X-rays to Measure Tesla Coil Voltage
From: DR.RESONANCE[SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent: Tuesday, September 23, 1997 11:13 AM
To: Tesla List
Subject: Re: Using X-rays to Measure Tesla Coil Voltage
To: Greg
Fr. McGahee actually described the technique we used. My friends used some
type of scintillation detector to measure the depth. This device was
connected to an oscilloscope which was calibrated to the system. We also
took calibration readings using the tube with a 100 kV power supply. Most
of our HV work was done in an excavated trench 12 feet deep so we had an
absorber of the radiation. We were over 300 feet away for safety. Very
similar to the calibration technique used with a field mill voltmeter --
which I found out later is a much easier way to measure the exact peak
output potential from a resonance transformer. Even though it is AC the
peaks represent the same value as the DC peaks. We made a large field mill
generating voltmeter (30 inch dia) and ocassionally use it to measure the
potential in clouds prior to (note I said prior to) a thunderstorm. The
field mill readings correlated with 2% of the x-ray readings and are much
less combersome to perform.
DR.RESONANCE-at-next-wave-dot-net
>
> From: Thomas McGahee[SMTP:tom_mcgahee-at-sigmais-dot-com]
> Sent: Tuesday, September 23, 1997 8:26 AM
> To: Tesla List
> Subject: Using X-rays to Measure Tesla Coil Voltage
>
>
>
>
> >
> > From: Greg Leyh[SMTP:lod-at-pacbell-dot-net]
> > Sent: Monday, September 22, 1997 5:25 PM
> > To: Tesla List
> > Subject: Re: Secondary voltage measurement.
> >
> > DR.RESONANCE wrote:
> >
> >
> > > The unit was our standard model M-150 running with a 14.4 kV pole
> xmfr as
> > > the power source. As to the measurement equipment, well, lets
> just say I
> > > have some friends at a local university who "borrowed"
> (unofficially of
> > > course --- and for only a 4 day period) some unique test
> equipment from a
> > > well equipped physics dept and they took the measurements. Can't
> say much
> > > more without shooting myself in the foot in case I might need
> some more
> > > equipment for short term use in the future.
> >
> > Can you at least mention the general principle behind the
> measurement?
> >
> > -GL
> >
> >
> Greg,
> When I was in high school in the mid 1960's I built (among other
> things) a number of homemade x-ray machines. These ranged all the way
> from 40KV to 250KV units. The intensity of the x-rays produced was a
> function of current. The penetrating ability of the x-rays was a
> function of voltage. I was able to "calibrate" my machines through
> the use of a set of stepped wedges that were made of strips of
> aluminum and steel. The higher the KV, the greater the thickness
> through which the x-rays could penetrate. I was able to get the
> radiology department of the local hospital to x-ray my step wedge in
> 25KV increments. Then I used the negatives to calibrate my step
> wedge.
>
> No matter how long an exposure I used, I could not get a 100KV unit
> to expose past the 100KV step on the calibration film. The method was
> quite effective. An intensifier screen could be used to reduce the
> exposure *time*, but the penetration level would be unaffected by the
> use of the screen.
>
> Instead of using film, I could have used a radiation detector such as
> a scintillation detector to determine the penetration depth in real
> time. Of course, such equipment might have barfed at the Radio
> Frequency fields that emanated from my apparatus (They were Tesla and
> Oudin coils, of course), but good old x-ray film is unperturbed by
> such things. Cheap and effective!
>
>
> Dr. Resonance may have been using a similar approach to measure the
> voltage of his Tesla coil. Or he may have been using some totally
> different and more esoteric approach. The bottom line, though, is
> that the use of x-ray penetrating ability is a very valid way to
> measure extremely high voltages. Also note that any voltage thus
> measured is actually a voltage that was measured under a certain
> amount of loading. If x-ray penetration says you got 1 MV, then you
> can absolutely believe it as being true.
>
> Hope this helps.
> Fr. Tom McGahee
>
>