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[Fwd: Cap Experiments and more ?????]

I never received this post I sent Friday night, so maybe
it got lost. Anyway, resending here for the list.
Bart

<<<< This post came and went through me just fine but it never
confirmed....  I don't know were it went. :-(  - Terry >>>>

Message-ID: <361EC695.7C7532A4-at-uswest-dot-net>
Date: Fri, 09 Oct 1998 21:29:41 -0500
From: "Barton B. Anderson" <mopar-at-uswest-dot-net>
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Subject: Re: Cap Experiments and more ?????
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Reinhard, All,
I re-rolled using .0015" poly (2 sheets for total of .003, measured) and 18" x
22" aluminum foil. This was a quick test and kept roll as tight as I could,
but
it was a really quick throw together. I didn't measure it flat as it was a too
large flat to truly get something to flatten it. So I rolled it up on an old
broom stick (minus the broom).

It measured 102.7nF. I went to the computer and the calculated value was
118nF,
much more realistic than yesterdays post. If I would have taken a little more
time to get the roll tighter, I'm suspect I would have hit very near the 118nF
mark.

So I unrolled it and this time used only one sheet between plates (.0015") and
smaller plates sizes (6.5" x 18"). This was a very tight role. I measured
55.2nF
and calculated 64.7nF. Since this was similar to the above test, I back
calculated K. K of 1.7 would match this as well as the above test. The poly
I'm
using probably has a k of 1.7 (maybe a little higher since this is a dry roll
test).

So Reinhard, my experiment in parallel with yours supports your findings
for the
most part. The garbage bag from my test yesterday was milk white and stated on
the bag as polyethylene. I don't was pure LDPE. Probably poly + other. K was
definitely NOT near 2.

My conclusion is that it's probably more the polyethylene purity vs. the
thickness as the poly.
Since both my test were calculated and measured at 3mils and 1.5mils
resulting in
nearly identical ratio's of K at 1.7. Also Reinhard, your first poly test was
nearly identical to my 1.5mil test here, and you were only able to achieve
~10nF
compared to my 55.2nF. It's got to be the poly.

Bart

Tesla List wrote:

> Original Poster: "Barton B. Anderson" <mopar-at-uswest-dot-net>
>
> Rienhard,
> I performed your same cap measurement. Except I the I didn't have the same
> poly,
> had only a trash bag (only 0.35mils). I ended up measuring 18.3nF flat, and
> 69.4nF
> rolled. I was way off the calculated. Your measured value compared to
> calculated
> was:
>
> Flat: ~6.5 times lower.
> Rolled: ~ 6 times lower.
>
> My measured value compared to calculated was:
>
> Flat: ~ 3.3 times lower.
> Rolled: ~5 times lower.
>
> I want to do this test again using better poly as well as compare thick vs.
> thin
> poly. I'm expecting with thin poly, the margin for error is huge compared
> to thick
> poly's. This may account for both our findings. Unfortunately I didn't get
> enough
> time tonight to get that far. I'll post my results in detail next time.
>
> Bart
>
> Tesla List wrote:
>
> > Original Poster: "Barton B. Anderson" <mopar-at-uswest-dot-net>
> >
> > I would at this time, try your other diectric under the same scenario of
> > tests and
> > see how that works out. If it was me, I might go as far as getting a
couple
> > alluminum sheets of some given size and try the test (who knows, maybe
it's
> > the
> > foil? everything should be considered). As a matter of fact, I have an old
> > flat
> > plate cap which was built out of alluminum sheets about 8" x 12" now
> > disassembled.
> > I might try this test myself tomorrow and see what happens with a
couple of
> > the
> > alluminum sheets.
> >