Measuring capacitor leakage current

[Animesh Maurya]

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

 

[Winfield Hill]

Animesh Maurya wrote...

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.

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

 

[John Woodgate]

I read in sci.electronics.design that Winfield Hill

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.

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.

 

[James Meyer]

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

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

 

[Stefan Heinzmann]

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.

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."

 

[R.Legg]

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.

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

Your method is probably adequate, however.

RL

 

[Animesh Maurya]

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

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

 

[Winfield Hill]

Animesh Maurya wrote...

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.

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