how stable is the parallel resistance of an electrolytic?
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 17th August 2014, 06:23 PM #1 ringing diyAudio Member   Join Date: Mar 2012 how stable is the parallel resistance of an electrolytic? Capacitors leaks current. So a real world capacitor is like an ideal capacitor with a parallel resistor (of course, series resistor and inductor, too.). The parallel resistor value seems to be high in some capacitor (10000 MOhm) and low in some electrolytics (less than one MOhm). Anyway, it that parallel resistor value stable with time (many years) and temperature as long as the capacitor is used well within the temperature and voltage spec?
 17th August 2014, 06:38 PM #2 ringing diyAudio Member   Join Date: Mar 2012 Often, the leakage current is given by 0.03*C*V or 3uA whichever is greater. So the parrallel resistor will be 1/(0.03*C). For example, an electrolytic capacitor with the spec of 470uF, 25VDC, will have a parallel resistor larger than 0.071 MOhm? Is this the right calculation? Anyway my question is whether that resistance value is constant over time, temperature variation (but far below 85 degrees C), etc.
 17th August 2014, 09:46 PM #3 JonSnell Electronic   diyAudio Member     Join Date: Dec 2012 Location: The Jurassic Coast, England. GB One should presume infinity resistance or the capacitor is leaky. __________________ Support for Fender, Marshall and all Valve Equipment; Audio Innovations, Audiorama FU29, Quad and Leak. www.jonsnell.co.uk
 17th August 2014, 09:52 PM #4 jcx   diyAudio Member   Join Date: Feb 2003 Location: .. Electrolytic Caps are best applied where their variable and/or poorly speced characteristics don't cause problems leakage current which can be indicative of parallel R is highly variable with temp, age - high leakage is often is often speced as one of "end of life" numbers
Kiriakos
Banned

Join Date: Jul 2014
Location: In from of my workbench
Quote:
 Originally Posted by ringing The parallel resistor value seems to be high in some capacitor (10000 MOhm) and low in some electrolytics (less than one MOhm).
Measured by what equipment ?
Do you own an LCR bridge meter ?

 17th August 2014, 10:00 PM #6 Conrad Hoffman   diyAudio Member   Join Date: Mar 2007 Location: Canandaigua, NY USA No, that resistance varies all over the place, with age, temperature, on-time and anything else you can think of. It's an interesting exercise to set up a power supply and measure leakage current with a series resistor and DVM. Do it. Vary everything and see what happens. You'll learn a lot. BTW, I don't think you have this problem, but don't confuse the simple parallel loss model with the DC leakage resistance term. __________________ I may be barking up the wrong tree, but at least I'm barking!
ringing
diyAudio Member

Join Date: Mar 2012
Quote:
 Originally Posted by Kiriakos Measured by what equipment ? Do you own an LCR bridge meter ?
I read the specs avaliable at Mousesr.

 17th August 2014, 10:57 PM #8 Kiriakos   Banned   Join Date: Jul 2014 Location: In from of my workbench Those specs are generic, nothing that you can use in sound applications.
 17th August 2014, 10:59 PM #9 kenpeter   diyAudio Member   Join Date: Nov 2007 Location: Dallas If parallel resistance is acceptable, you just need to know what it is? You could put a known stable resistor (perhaps 100K) in parallel. That should swamp the unknown possibly non-linear component.
ringing
diyAudio Member

Join Date: Mar 2012
Quote:
 Originally Posted by kenpeter If parallel resistance is acceptable, you just need to know what it is? You could put a known stable resistor (perhaps 100K) in parallel. That should swamp the unknown possibly non-linear component.
If the parallel resistance changes (with age, temperature, etc.) +/- 60% from 1000 MOhm, it would not matter much for me. If it changes +/- 60% from 0.2 MOhm, it matters.

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