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This is more a theoretical question.

I have a DC circuit with multiple capacitors with different voltages. Because I need to know how much current my circuit needs over a longer time, I calculated all the capacitor leakage currents which are around 0.8 uA. When measuring the current of my device while running, I only have around 0.3 uA. It was measured with a uA Multimeter in series with the DC source.

For the calculation of the capacitor Leakage currents, I used the given values in the datasheet at room temperature.

My question now is:

Why is my current so much lower than my calculated value when measuring the circuit? Are the values in the datasheet more suggestions or how am I to interpret the insulation resistance?

Unfortunately, I am not able to provide any schematics for this question.

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  • \$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$
    – Community Bot
    Oct 7, 2021 at 7:55
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    \$\begingroup\$ I edited the post, i hope its more clear now \$\endgroup\$
    – Lyoner
    Oct 7, 2021 at 8:30
  • \$\begingroup\$ the leakage is usually a worst-case value, since the minimum is zero (ideal cap). Also they usually quote the maximum after some stress (temperature and/or time) \$\endgroup\$ Oct 18, 2021 at 6:52

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The figure given in datasheets is usually a maximum, especially for 'defect' characteristics like leakage current. If you've measured well below that on some particular samples you have in front of you, then that's excellent, the devices meet their specification by a good margin.

If you're going to design equipment that uses these though, design for the full data sheet leakage current. The next capacitors you buy may only meet their specification, not exceed it by such a good margin.

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  • \$\begingroup\$ Thank you! that's interesting. Now there might not be a chance for me to calculate the value for the leakage current. Only the max. So if I need it to be under 0.3uA under all circumstances I should find capacitors with a higher insulation resistance. Did I interpret this right? \$\endgroup\$
    – Lyoner
    Oct 7, 2021 at 8:32
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    \$\begingroup\$ @Leo If you need it to be under 300 nA under all circumstances, then you need to find capacitors specified for that. \$\endgroup\$
    – Neil_UK
    Oct 7, 2021 at 11:35

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