From: "Malcolm Watts"
Date: Mon, 16 Oct 2000 09:13:42 +1300
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.