From: Winfield Hill
Subject: Re: Low leakage parts
Date: 4 Jan 2003 17:54:36 -0800
Organization: Rowland Institute
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> Tom Bruhns wrote ...
>> the roughly 0.1fA of leakage I'm seeing in 0.1uF polyprop caps
>> at 10V suggests about 10^17 ohms effective shunt resistance,
> ** The insulation resistance for some ( LCR brand)
> polypropylene caps (if that is what you used) is quoted in the
> Farnell cat as 1 x 10^11 ohms. For LCR polystyrene it is given
> as 5 x 10^11 ohms.
> Your suggested figure is some one million times better.
> My doubts are reasonable.
Phil, your doubt are NOT reasonable, quite the contrary. That's
because you Are doubting engineers who have far better knowledge,
skill, experience and equipment than yourself.
In this thread you have been and are systematically doubting Tom's
measurements and insights, while putting up weak irrelevant points
to defend your doubts. Tom has measured what he says he's measured.
For you to postulate conditions he didn't experience is wrong and
irrelevant. [I have further opinions, but I'll remain silent.]
Furthermore some of the rest of us have made similar measurements,
are aware of "official" laboratory measurements on the properties
of air, etc., and have therefore repeatedly offered our opinion on
the reliability of Tom's reports, which knowledge and opinion you
As for your Farnell data, those are WORST case specs, thankfully
rarely seen in practice. A production engineer ignores them at
his peril, but you cannot use them to argue against laboratory
component measurements made by skilled engineers who know better
than you what they are doing.
For these reasons I say, "Drop it: Your doubts are NOT reasonable."