Comparing The ESR Of Two Caps....

[He's Dead Jim]

if i have a good cap and a questionable cap of the same values, do they need to be from the same manufacturer to do a proper comparison to find if the questionable one is bad??

also, is there any way or formula, besides 10 years of experience, to find the proper esr value from the other values on the data sheet??

i must have looked at at least 100 data sheets from about 10 different manufacturers in the past hour and not one of them listed an esr value...

thanks...

(p.s. - i just got my "blue" esr meter today, thanks bob)

[KeriJane]

Re: Comparing The ESR Of Two Caps....

Hi H D J!

Do two caps have to be from the same manufacturer to be compared?
No. But they do have to be of a compatible series as well as capacity and voltage.
Sometimes you might come across a cross-reference like this one:
Panasonic NHG Series Cross References: Nippon Chemicon KHG, Nichicon VZ, Elna RJ-4, Rubycon YXA

If the ESR value isn't on the Data Sheet, it is probably a General Purpose (GP) cap. Apparently ESR isn't a high priority for GP caps.
I think that maybe the sticker on the front of the Blue meter gives a good general indication of what could be considered "Low Enough" for such caps.

I do know that all of the "low ESR" caps I've tested test far lower (better) than the sticker would consider OK while the few "GP" caps I've tested are much closer to the sticker's graph.

Have Fun!
Keri

[He's Dead Jim]

Re: Comparing The ESR Of Two Caps....

thanks for the quick answer....

i'm gonna make a chart up as i go along of new v.s bad/dead caps....

we'll see how it pans out...

[PCBONEZ]

Re: Comparing The ESR Of Two Caps....

ESR may not say ESR in data table but units will be something like:

mΩ at 20°C and 100kHz
or
Ω at 20°C and 100kHz

[Those are standard measurement conditions. Some brands 'cheat'.]

Often charts say something like:
Impedance in mΩ at 20°C and 100kHz
or
Impedance in Ω at 20°C and 100kHz

Technically Xc is included in that but Xc is small there and the same for a given uF.
In other words if you have two 1000uF caps:
.. one with .030 Ω at 20°C and 100kHz
.. the other with .040 Ω at 20°C and 100kHz
Since Xc is the same the .010 Ω difference is all due to ESR difference.

Conversion
10 mΩ = .010 Ω

[He's Dead Jim]

Re: Comparing The ESR Of Two Caps....

unfortunately, most of the data sheets i looked at so far have an esr column, but it's always blank...

but you gave me a bunch of other values to check...

thanks..