# Re: Measurements using field probe (fwd)

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---------- Forwarded message ----------
Date: Tue, 7 Jul 1998 08:24:08 -0600
From: "D.C. Cox" <DR.RESONANCE-at-next-wave-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Measurements using field probe (fwd)

Hi John:

The field mill meter actually measures the potential difference and is
usually used with a calibration voltage.  We use 150 kV DC to calibrate our
units, and then the potential is directly proportional to the distance from
the measured terminal.  Wouldn't the AC peak be equal to 1.4 x Erms?  This
would mean the ACpeak should be equal to the DCpeak.  Example, if you use a
common 1N4007 to rectify the AC line which is 120 VAC Erms, then the DC
reading is around 170 volts.  This is the same as measuring the AC line
with a meter than is not a true RMS meter and gives only the peak AC
reading --- again around 170 volts.

DR.RESONANCE-at-next-wave-dot-net

----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Measurements using field probe (fwd)
> Date: Monday, July 06, 1998 10:44 PM
>
>
>
> ---------- Forwarded message ----------
> Date: Mon, 6 Jul 1998 03:03:20 +0000
> From: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: Measurements using field probe
>
>
>
>   DR RESONANCE -
>
>   If I understand your question correctly, I would say the AC peak
potential
> would be 1.4 times the VDGRF potential which is DC. The DC potential
would
> be equal to the RMS value of the AC potential.
>
>   It is my understanding that the field mill voltmeter measures the
electric
> field intensity instead of the potential around a charged object. The
field
> mill voltlmeter requires an antenna and ground that would measure the
> electromagnetic field similar to a radio field strength meter. The field
> intensity varies as the square of the distance compared to the potential
> method that varies directly as the distance.
>
>   I have never built or used a field mill voltmeter so have limited
> knowledge of their operation. I would think this would be a method to
> measure the TC secondary voltage in a roundabout way. The field mill
> voltmeter is used to measure the voltage of a lightning strike and could
be
> used to measure the TC secondary terminal voltage. However, the
> instrumentation and calculations would be more complex compared to
finding
> the VDG generator voltage. How did you convert the intensity data to a
> voltage at the TC?
>
>   The voltage indicated by   sqrt(Ls/Lp)  requires additional factors
that
> are not easy to find. I have not had much success in using this
relationship
> in a program. The TC sec voltage depends on other factors such as input
> watts, etc.
>
>   I believe that determining the voltage on the TC secondary is possible
but
> is going to take a lot of research. The  research that you, Terry Fritz,
and
> others have done  has apparently made much progress.
>
>   John Couture
>
> -----------------------------------------------------
>
>
> At 12:33 AM 7/4/98 -0500, you wrote:
> >
> >
> >----------
> >From:  D.C. Cox [SMTP:DR.RESONANCE-at-next-wave-dot-net]
> >Sent:  Friday, July 03, 1998 11:33 AM
> >To:  Tesla List
> >Subject:  Re: Measurements using field probe
> >
> >to: John
> >
> >Wouldn't the peak potential be the same with either TC or VDGRF?  I used
an
> >electrostatic generating field mill voltmeter and measured the peaks
with
> >similar results to that predicted by the SQR Ls/Lp equation.  Comments.
> >
> >DR.RESONANCE-at-next-wave-dot-net
> >
> >
> >----------
> >> From: Tesla List <tesla-at-pupman-dot-com>
> >> To: 'Tesla List' <tesla-at-pupman-dot-com>
> >> Subject: Measurements using field probe
> >> Date: Thursday, July 02, 1998 9:49 PM
> >>
> >>
> >> ----------
> >> From:  John H. Couture [SMTP:couturejh-at-worldnet.att-dot-net]
> >> Sent:  Thursday, July 02, 1998 2:01 PM
> >> To:  Tesla List
> >> Subject:  Re: Measurements using field probe
> >>
> >>
> >>   Terry, All -
> >>
> >>   Your experiments on measuring the voltage on the TC secondary
terminal
> >are
> >> interesting and instructive. I thought you would be interested in
tests I
> >> did several years ago to check the voltage on the Morris and Lee 250
KV
> >Van
> >> De Graaff generator. I got 241 KV which was close enough.  This is
> >similar
> >> but not exactly what you are doing.
> >>
> >>   The VDG generator charges a terminal with DC not AC like a Tesla
coil.
> >A
> >> charged object in space can be detected in two ways, either by the
> >potential
> >> it produces or by the force it produces. These tests require two
> >different
> >> methods and two different equations. The potential varies directly as
the
> >> distance and the force varies as the square of the distance.
> >>
> >>   To detect the potential of the charged VDG terminal I used a 2 inch
dia
> >> brass door knob connected to an electrostatic voltmeter. The setup and
> >> calculations are simple but electrostatic units are used which are not
> >> familiar to most coilers. The equation is:
> >>
> >>       Stat Volts = Stat Coulombs/cm
> >>
> >>   This equation has the advantage that it combines the three important
> >> parameters, that is, volts, coulombs, and distance. This equation
tells
> >us
> >> that the charged object (statcoulombs) produces a potential
(statvolts)
> >at a
> >> certain distance (CM). The electrostatic  potential varies directly as
> >the
> >> distance and can easily be found for any distance from the object with
> >the
> >> electrostatic voltmeter. Note that this test is not the same as the