If I have an electrolytic capacitor (let us use a 30 year old unit for arguments sake) that measures very low ESR (not shorted!), can I assume the capacitance will still be within tolerance?
If I have an electrolytic capacitor (let us use a 30 year old unit for arguments sake) that measures very low ESR (not shorted!), can I assume the capacitance will still be within tolerance?
Pretty well - ESR is directly (inversely) related to capacitance, so if the ESR is low, then the capacitance is likely to still be good.
The opposite isn't true, if the capacitance is within spec, it's no guarantee that the ESR is still low - my ESR meter displays both capacitance and ESR, and in a high percentage (probably around 50%?) the duff cap is still within spec for it's value, but the ESR is completely shot. The ones I measured yesterday all read within spec, but the ESR read >20 ohms (which is as high as it reads).
If a cap ESR's OK, I wouldn't consider it worth changing, unless it's a known failing type - such as CapXon.
Thanks Nigel, that is helpful to know.
I actually have all the bits to make myself a rather nice (I think) ESR meter from Elektor, which measures both esr & capacitance, measures very high values too, however my attempt at making a PCB failed due to me having a brother laser (organic ink) so that project is on the 'to do' list atm!
Thanks Nigel, that is helpful to know.
I actually have all the bits to make myself a rather nice (I think) ESR meter from Elektor, which measures both esr & capacitance, measures very high values too, however my attempt at making a PCB failed due to me having a brother laser (organic ink) so that project is on the 'to do' list atm!
Yes I have considered that one Nigel, as I have their semiconductor tester which has served its purpose well for a number of years!
Anyway, as I have purchased 90% of the Elektor jobby I might as well finish it now!
Thanks,