# Re: Measurements using field probe (fwd)

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---------- 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

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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 radio
>> field strength meter test.
>>
>>   The details on using electrostatic units can be found in electrical
>> engineering handbooks and physics texts.
>>
>>   John Couture
>>
>>
>
>
>

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