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simonwai999
Joined: 30 Jun 2008
Posts: 113
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 17 Aug 2008 8:31 CAP leakage |
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hi
how can we tell if an electrolytic cap is leaking or not?
thanks
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Kral
Joined: 28 Mar 2005
Posts: 1014
Helped: 165
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| 17 Aug 2008 18:44 Re: CAP leakage |
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simonwai999,
If you can remove the cap from its circuit, then charge it up to a voltage. Then remove (open) the charging source. Monitor the voltage at periodic intervals using a high input resistance meter. from these measurements, calculate the initial slope (dv/dt) of the discharge curve. The leakage current is equal to C dv/dt. Compare this to the manufacturer's specified maximum leakage current for the capacitor.
regards,
Kral
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simonwai999
Joined: 30 Jun 2008
Posts: 113
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| 17 Aug 2008 19:27 Re: CAP leakage |
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hi thanks carl
sounds complicated to me tho lol
i do not even know what dv is
thanks
regards
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FvM
Joined: 22 Jan 2008
Posts: 2635
Helped: 431
Location: Bochum, Germany
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| 17 Aug 2008 19:47 Re: CAP leakage |
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Any electrolytic capacitor has a small residual (leakage) current. So the question should be: leaking beyond specification?
For small, low voltage caps, a leakage current of several uA is usually allowed by manufacturer specification. If a ohmmeter shows above Mohm after some minutes, the specification is probably met.
Are you still behind the mysterious condenser and electret mics topic?
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Kral
Joined: 28 Mar 2005
Posts: 1014
Helped: 165
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| 17 Aug 2008 21:20 Re: CAP leakage |
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simonwai999,
Sorry if my answer was too brief. dv/dt is a differential calculus term that sounds more complicated than it really is. It is simply the rate of change of voltage with respect to time. If, after you remove the charging voltage, you draw a graph of the voltage (vertical axis) vs time (horizontal axis), then dv/dt is the slope of the line near the origin (t = 0). If you draw a straight line that is tangent to the curve at t=0, then dv/dt is just the slope of the straigh line.
Regards,
Kral
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simonwai999
Joined: 30 Jun 2008
Posts: 113
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| 18 Aug 2008 5:58 Re: CAP leakage |
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hi folks
thanks for your reply
yes lol i am still thinking about that circuit a lot of people said it would be the problem a leaking cap or a bad one
today I am gonna get some more new caps and try again
thanks
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