Measurements using field probe
From: terryf-at-verinet-dot-com <terryf-at-verinet-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Date: Wednesday, July 01, 1998 12:58 PM
Subject: Re: Measurements using field probe
Hi again Antonio,
The 4 x pi x R^2 error found its way into my original calculations in
the report. After playing with some field charts and experimenting, I now
believe my "luck" at getting the third calibration method to work was just
luck. The field distortion from the ground, ceiling, etc. does add
significant error. It is far better to calibrate using one of the first two
methods that I mentioned in yesterday's post. One should also mark how the
antenna is positioned to be sure that once it is calibrated it does not
move. I was having problems using the third method in other situations and
this explains it. I need to update a few things in the report anyway so
this will be added to the revision. Many thanks for pointing this out.
Since Ca is typically 1/1000000 Cl, I dropped the term for
Also, I should mention that the Maxwell equation I=$ J.ds and some
of the other integral equations in the original report were simplified from
their rigorous forms. In our case, the simplified forms are valid.
Thanks for catching the error.
At 11:06 PM 6/30/98 -0500, you wrote:
>From: Antonio Carlos M. de Queiroz [SMTP:acmq-at-compuland-dot-com.br]
>Sent: Tuesday, June 30, 1998 11:05 PM
>To: Tesla List
>Subject: Re: Measurements using field probe
>Terry Fritz wrote:
>First, congratulations for your excellent work. I have just the few
>below. Please correct me if I am not seing something.
>> These are the equations that govern the voltage and current probe
>> Voltage Probe
>> Vov = ( Ca / Cl ) Vs
>Vov = Ca/(Ca+Cl) Vs, but the difference is small.
>> Current Probe
>> Voc = Rl ( Aa / (pi x R^2) ) ) Is
>Voc = Rl ( Aa / (4 x pi x R^2) ) Is, as the surface area of a sphere is 4 x
pi x R^2.
>> Note that the area between the coil and the antennas should be free from
>> large objects and such that may disturb the electrostatic fields being
>> picked up.
>Ideally, this includes the ground and the secondary coil. Due to this,
>measurements may vary significantly depending on where the probes are (side
>of the coil, top of the coil). A calibration procedure is necessary for
>Antonio Carlos M. de Queiroz