Hi guys, been away for a couple of weeks.
As I wrote before, I did some measurements on capacitors / leakages, intended for DC biased measurements.
Now I made some more measurements, this time I charged the caps to 7.1V and let them stand for one week for self discharge.
The results are ballpark the same as before but "better" tanks to longer time and better procedure.
Still a polystyrene top the list followed by polypros. Still a RIFA (Kemet) PEH169 industrial elyth is giving really good results.
I attach results. The second last column is the cap type leakage characteristic, the last column scaled by capacitance.
Some previously tested caps have been excluded now. Before the tests, the caps had been charged and left to rest for two days. Still, several e-caps have had higher voltage now than a week ago, i.e. very strong memory effect / dielectric absorption. Those results are not included here. I will measure them again in a week but if the DA is that high, they will act as non-linear LP filters with very un-predictable characteristics.
I also added a few new caps to the test set but it seems too early to draw conclusions:
- Russian "wet slug" tantalum-silver, 25V, 300uF
- More RIFA PEH169, 2200uF 63V
- Motor starter polypro, 800uF
Preliminarily,
- one tantalum-silver cap was quite good, the other quite bad.
- the RIFA, one cap was quite good, the other quite bad.
- the motor starter polypro; really bad.
I will charge them up to high voltage / take them down and se if any of them recover.
A comment; one needs very high impedance meters for this. My DMM has >20Gohm input and this still discharges "small" caps, like 10uF in the order of 1mV / second which makes measurements a bit demanding, when the capacitor self discharge is only tens of millivolts in a week. Thinking of a terra-ohm input buffer and DMM synced FET switch.