From: "Terrell W. Fritz"
Date: Sun, 15 Oct 2000 17:05:07 -0600
Subject: Re: [TSSP] Surprising secondary voltage profiles
Hi All, I have a CW coil. It drives about 900 watts at 350kHz. It is driven from a commercial plasma power supply which is very stable. I can easily control forward power. Could I plot an equipotential contour around it with a low Z probe of some type that would have minimal effect. I was thinking like a neon bulb on the end of some benign rod. Something that would not affect the coil much. I can easily set the power down below breakout. I think you can put a resistor between the leads of the neon bulb to control it's sensitivity. Perhaps the detuning technique I used in late 87 with the non-linear coils experiment to map the field around those coils: http://users.better.org/tfritz/site/papers/nonlinearcoils/NonLin.html I think Dr. Rzeszotarski has done this. Any ideas on set up or what to use for a probe, especially the rod holding it, would be great. Perhaps a thin wood dowel or balsa wood rod. Styrofoam is supposed to be pretty transparent to electrical fields but it may be too weak... I will try and post some details of the CW coil (a long overdue task)... I suppose I would need some X-Y frame to find the exact position to lamp lights. I would think getting a pretty accurate map of the E-field around a powerful stable CW coil would be within the reach of our modern equipment and knowledge. I would hope such a test could answer this convex/concave thing. Cheers, Terry At 09:13 AM 10/16/2000 +1300, you wrote: >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.