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Low leakage capacitors

Hi,

I'm trying to find the lowest leakage capacitor, somewhere in the range of 0.01uF to 1uF, *might* be able to live with 0.001uF, for DC use. I'm not sure if PTFE (teflon) is the best choice, but here's one

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It says, "Insulation Resistance: 1000 M=A5=D8*=A5=ECF Need not exceed 100,0=

00 M=A5=D8 at 25 =A8=ACC" What exactly do they mean by "Need not exceed 100,000 M=A5= =D8" ?

Also I heard polystyrene is good.

I've performed various RC time constant tests on caps by placing a voltage source on the cap for a period of time, removing the voltage source and time it, then measure the DC voltage after a certain time period, and calculate the parallel resistance. It appears that the longer the voltage source is held on the cap results in more parallel resistance-- possibly dielectric absorption.

So this makes it more difficult to find the best type of caps for this use. IOW, perhaps one cap might have less leakage after 1 minute, but after 10 hours perhaps another type of cap might have less leakage.

I'm looking for a cap that would contain as much charge as possible for about one day. The voltage levels are around 1 volt.

Any help is greatly appreciated! Paul

Reply to
Paul
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Paul wrote in news:6ac514c1-4564-438d-9294- snipped-for-privacy@d19g2000prh.googlegroups.com:

Exploring what people use for sample/hold circuits might be the way to narrow it down. The requirements are very low dielectric absorbtion, usually low voltage at DC or of moderately changing signals.

Somewhere (I forget where) I read of a sample/hold op-amp circuit that not only had a very high resistance input, but some sort of regenerative ability to prolong the life of the charge on the cap on its input. I'm not sure if this is what you're after, but it might be worth hunting for.

Bob Pease has a page:

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Amongst other things it shows a way to get better than teflon's performance witha polypropylene cap. It looks like a different scheme than the one I saw once but the intent is the same.

Reply to
Lostgallifreyan

Have you considered glass !

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Best Regards:
                     Baron.
Reply to
Baron

Baron wrote in news:gtffio$ugf$ snipped-for-privacy@news.motzarella.org:

I know I hadn't, but it's a cool idea:

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Reply to
Lostgallifreyan

Post back and lets know how it goes.

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Best Regards:
                     Baron.
Reply to
Baron

re : lowest leakage caps : a high voltage film like teflon or polysulfone would be ok if space is not a problem. Otherwise ELNA makes low leakage caps the size of regular RB and RT electros, specifically designed for timing circuits.

jcdrisc

Reply to
jcdrisc

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