From: "Terrell W. Fritz"
Date: Mon, 16 Oct 2000 08:00:44 -0600
Subject: Re: [TSSP] Surprising secondary voltage profiles
Hi,
I have a terminal that has a current transducer inside it that goes off to
fiber optic. I don't know how you would do the ground reference for a
voltage divider. I can get the paper from Gary if it would be of use. I
think he is on the regular list and I have his E-mail somewhere...
Pictures of my current sensing terminal are at:
http://63.225.104.49/TeslaCoils/Misc/ProbeTerminal/
Cheers,
Terry
At 11:20 PM 10/15/2000 +0100, you wrote:
>Greetings all.
>
>Wasn't there an article from a Dr Gary Johnson in USA on making a capacitive
>voltage divider, which lived on the toroid and passed it's divided-ratio
>information down a length of fibre-optic cable? This approach seemed not to
>disturb any of the field geometry.
>
>we spoke on the Pupman list about it ages ago: the idea that was suggested
>at the time was to build the electronics inside the toroid, thus placing it
>in a zero field gradient; at which point an FM radiio link could maybe do
>the job.
>
>the reference that I have on my book shelf is
>
>" Prcoeedings of the 1992 International Tesla Symposium", and the article
>was page 93, "Tesla Coil Instrumentation". The name of the author is indeed
>Gary johnson, from Kansas State University, Dept of Elec. Eng.
>
>The article is quite good (in contrast to the other articles in that book)
>but Johnson reckoned that you should see VSWRs of "100 or more" whereas all
>my previous work has seen values of half that figure from memory.
>
>Richard Craven, Malvern, England
>
>
>----- Original Message -----
>From: "Malcolm Watts"
>To:
>Sent: Sunday, October 15, 2000 9:13 PM
>Subject: Re: [TSSP] Surprising secondary voltage profiles
>
>
>> Hi all,
>> I'd be a bit wary of any measurements which rely on
>> placing a probe close to the coil, no matter how small the
>> probe is. I remind all of the "gimmick" capacitor beloved of
>> super-regenerative radio set builders. Distance is the key
>> here. I just wanted to put in a cautionary note here. I
>> realise it is a nightmare to probe a low capacitance structure
>> without upsetting it. A possible way forward would be to probe
>> a set of equipotential rings of some significantly greater
>> diameter than the secondary. If the capacitance to ground of
>> the non-probed rings was adjusted to compensate for the ring
>> being probed..............
>>
>> gnd----||-------o o o o
>> o o
>> gnd----||-------o o o o
>> o o
>> scope-------------o o o o
>> o o
>> gnd----||-------o o o o
>> o o
>>
>> Some shunt R for each compensating cap to match that of the
>> probe would also be required I would think. This of course
>> assumes that each C is equal to the scope and might need to be
>> adjusted to allow for the normal difference in proximity to
>> ground of the various portions of the secondary. The major
>> point about this is how to avoid distorting the electric
>> fields.
>>
>> Regards,
>> Malcolm
>>
>
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.