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Measuring capacitor leakage current

Discussion in 'Electronic Basics' started by Animesh Maurya, Feb 26, 2004.

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  1. How is capacitor leakage current measured?

    Even after fully charging 2200uF cap to 3V, when I placed my
    multimeter in series it displayed about 1uA current.

    Is it the capacitor leakage current.

    But after half an hour current surprisingly dropped to 0A.

    Thanks to all

    Animesh Maurya

    e-mail address is invalid
     
  2. Animesh Maurya wrote...
    No, not leakage current. What you were observing is due to
    dielectric absorption. This effect means that portions of
    the capacitor remembered the previous voltage (discharged)
    and were responding more slowly to the voltage change.

    Thanks,
    - Win

    whill_at_picovolt-dot-com
     
  3. I read in sci.electronics.design that Winfield Hill
    While that is strictly correct, that 1 uA current has just the same
    effects (if any) on your circuit as if it were leakage current. The only
    difference is that after a while, it disappears, as you have observed.
     
  4. James Meyer

    James Meyer Guest

    2200uF at 3 volts sounds a lot like an electrolytic capacitor to me.
    Most likely an aluminum electrolytic. In that case, the 1uA current may be
    related to "forming" currents. If it is forming current, then it will likely
    not be the same 1uA after one or more charge/discharge cycles.

    Jim
     
  5. A quote from the CDE Application Guide Aluminum Electrolytic Capacitors:

    "DC Leakage Current (DCL)

    DC Leakage Current is the DC current flowing through the
    capacitor with the rated voltage applied. The value of leakage
    current depends on the voltage applied, the charging
    period and capacitor temperature.

    DCL Method of measurement

    Measure leakage current at 25 °C with the rated voltage
    applied through a protective resistance of 1000 Ohm in series
    with the capacitor in the measuring circuit. Five minutes
    after the application of voltage, the leakage current is not to
    exceed the maximum value indicated in the specification."
     
  6. R.Legg

    R.Legg Guest

    0.0000000 Amps is a very small current, requiring some very accurate
    equipment to measure.

    Your method is probably adequate, however.

    RL
     
  7. If this current is due to dielectric absorption then what is the cause
    of leakage current.

    Is there any specific term to define the above current, or we simply
    call it dielectric absorption current.

    Thanks again,

    Animesh Maurya
     
  8. Animesh Maurya wrote...
    Right, here's a typical model, the trick is knowing
    the R values. :>)

    | C/2
    | ----+--------||--------+-----
    | | |
    | +----||----/\/\----+ C/4
    | | |
    | +----||----/\/\----+ C/8
    | | |
    | +----||----/\/\----+ C/16
    | | |
    | +----||----/\/\----+ C/32
    | | |
    | +----||----/\/\----+ C/64
    | | ... etc ... |
    | | |
    | '------/\/\--------'

    The bottom element is leakage, and is not directly
    related to the other values.

    |

    Thanks,
    - Win

    whill_at_picovolt-dot-com
     
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