Re: oil for caps (fwd)
---------- Forwarded message ----------
Date: Mon, 12 Jan 1998 13:27:33 EST
From: Esondrmn <Esondrmn-at-aol-dot-com>
Subject: Re: oil for caps (fwd)
In a message dated 98-01-09 02:01:20 EST, you write:
- snip -
I made the original post re SUNISO oil and its apparent effect of
increasing the expected capacitance of a stacked plate cap (aluminium
litho plates and polystyrene dielectric).
I was concerned that possibly my findings were in error, so I set up a
small test as follows:-
I built a very rudimentary cap consisting of 4 aluminium litho plates
7" x 5" separated with 3 sheets of polystyrene 1/16" thick.
The unit was taped together and the capacitance measured with a
Parameters 7060 multimeter as .000635 uF.
I then lowered the unit still connected to the multimeter into a
container full of Suniso 3GS refrigeration oil.
The capacitance steadily rose as the capillary action sucked the oil
between the plates to .000747uF. But stopped there due to air trapped in
the centre of each plate.
I dismantled the stacked plate and reassembled wet (painted each plate
with oil) and the measured capacitance was .000859uF.
This was only a quick and dirty experiment which you can all duplicate
with virtually no expense. The results show quite clearly that the
Suniso 3GS oil does in fact increase the expected capacitance. This
particular test did not show an increase of 100%, but never the less
there is an increase.
My original cap ((.02uF) - which should have been .01uF using the TESLAC
program) is still functioning and hasn't missed a beat in 2 years! is
used with 4 x 10kv 30mA neon trannies in parallel driving a 9" x 25"
secondary, with a 1/4" copper flat spiral primary - 9 turns tapped at
7.5 - produces 4 foot streamers consistently using a single spark gap
(brass coach bolts - about 1/4" gap).
I thought the original question here was whether or not one type of oil will
yield a higher capacitance value (significantly higher, like double) when
compared to say mineral oil. Your test shows that a cap with polystrene and
oil produces more capacitance than a cap with polystrene and air. No argument
here, I would expect that. I calculate that your test cap should produce
about 978 pf - and you measure a little less, which is also expected as the
caps we normally build end up with a spacing between plates a little more than
the measured thickness of the dielectric due to everything not being perfectly
flat and insuffecient pressure holding the plates together.
Once again, I maintain that the selection of the type of oil will not
dramatically affect the capacitance value achieved.