The method I use to check for faulty capacitor is to check for ESR, impedance or Dissipation factor /loss tangent value according to the datasheet, and if can't find a datasheet then i'll check the capacitor based on the value given by the meter, like the MESR100 does. However, a lot of datasheets have leakage test and I'm just wondering how important is it to test for leakage if you've already checked above values?
If the capacitor has a specified leakage and it's in a circuit where this is important, then if you suspect a problem with leakage, yes it's worth checking it.
Did you say you check for the actual capacitance?
Did you say you check for the actual capacitance?
LOL, i forgot to mention i also check for capacitance, the first thing I do.
This means now that I need to find a meter of some sort to test for current leakage, maybe something like a Applent AT680?
Yes, my old heathkit LCR bridge provided leakage tests with a rotary switch that stepped the test voltage up to 600VDC.
Actually, leakage isn't difficult to test. All it requires is a dc voltage source near but below the cap's max rating, current limiting resistor and an Ammeter capable of reading uA. That's just about all modern DMM's.
Chris
Actually, leakage isn't difficult to test. All it requires is a dc voltage source near but below the cap's max rating, current limiting resistor and an Ammeter capable of reading uA. That's just about all modern DMM's.
Chris
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How are you testing the capacitance out of interest. Do you take into account the DC bias issue with MLCCs?
Thanks
Adam
Thanks
Adam
Steve, that pdf is confusing. On the first page it discusses FiG 1 schematic and then points the reader to FIG 2 that includes a Diode (Ds). The text further discusses the purpose of Ds but it doesn't exist? 
Chris
Chris
Steve, that pdf is confusing. On the first page it discusses FiG 1 schematic and then points the reader to FIG 2 that includes a Diode (Ds). The text further discusses the purpose of Ds but it doesn't exist?
Chris
Pheww, thought it was only me LOL
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See page 4-14 of this for the conceptual diagram. It doesn't include the switch that is required for practical purposes, and if you follow the instructions for discharge, it is clear that the diode is between the switch and the electrometer (unless you use a low voltage zener diode). In any case, the switch needs to be in the shielded box because it is effectively connected to the input of the electrometer.
If you're using a standard multimeter, the noise limiting action of the resistor and diode are not going to be of practical importance because you're measuring such large currents (fractions of a uA)
If you're using a standard multimeter, the noise limiting action of the resistor and diode are not going to be of practical importance because you're measuring such large currents (fractions of a uA)
My Heathkit IT-11 uses an older method called Power Factor rather than ESR.....
For actual ESR measurements Ive restored both a Genrad 1650 and a Heathkit IB-2A and put them toe to toe to see how they performed. Obviously the Genrad is a whole different class, and wins in eqase of use, but the heathkit didnt do too bad.
Ultimately for DC cap leakage, my IT-11 is most often used, and for the most specific measurements, a uA meter is run in-line of the leak-down test
For actual ESR measurements Ive restored both a Genrad 1650 and a Heathkit IB-2A and put them toe to toe to see how they performed. Obviously the Genrad is a whole different class, and wins in eqase of use, but the heathkit didnt do too bad.
Ultimately for DC cap leakage, my IT-11 is most often used, and for the most specific measurements, a uA meter is run in-line of the leak-down test
The IT-11 Was also somewhat short lived and replaced by a similar model that did not allow the switch to remain in the test position because it was too dangerous so they made the new one spring loaded. That means you could not use it to reform capacitors after the upgrade. Granted, I've shown movie after movie why trying to reform capacitors that are 50 or 60 years old is a bad idea anyway, but it was a short lived feature.
I believe the Heathkit IT-11 termed it Power Factor because that measurement was intended for electro's only. It was a measurement of combined ESR and leakage that manifests itself as real power dissipated by the cap, which also reduced it's effective capacitance.
I still have mine but it needs new electro's for the high voltage supply.
Chris
I still have mine but it needs new electro's for the high voltage supply.
Chris
