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Re: Terry's New Plane Wave Antenna
Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
Hi Paul,
.........
Consequently, this is probably a more reliable measurement.
It would be interesting to repeat these experiments, to witness
the space charge collecting on an electrode over a period
of seconds or longer. Naturally, Terry's plane wave antenna
would make a good charge collector!
:-)
Terry wrote:
> my perhaps ill named "plane wave" antenna was meant to pick
> up a large "current area".
And it should work for this collected charge just as well as
for induced charge.
I see the reasoning behind 'plane', and as you say, much better
than a wire electrode from the point of view of source
capacitance. I can only continue to object to 'wave'.
> Insulators are like batteries
Too right! In some of my experiments the charge that happens to
reside on the *outside* of the insulated connecting leads of a test
circuit becomes a problem, and I have to switch to using bare wires!
Gosh!! I never thought about wire insulation and it messing with the
charges... I am sure there are many other odd sources of
error... Maybe they can all be "calculated out" in one lump somehow...
Are we going to see a thread 'How to build an electrometer' now?
Mine is all done :o))
http://hot-streamer.com/temp/pw-010.JPG
The HP DVM has a >10G ohm input impedance setting. So I set the
impedance up and just connected it to the antenna. I think I just
need to measure the total input capacitance now (meter, cable,
antenna, 20nF cap...) and I should be all set. The capacitance is
pretty high for these meters at >20nF but it seems to work well with
the very sensitive meter. It happily drifts around fairly randomly
but slowly so it seems to work... As I put my hand near it, it seems
pretty repeatable and all...
I just flip it over to the current setting which discharges
everything. It also has a "null" setting which zeros the display
with a relative function.
Cheers,
Terry
--
Paul Nicholson
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