Measuring caps

[trodas]

Measuring caps using ESR60 Enhanced tool, that have this specs:
Capacitance: 1 - 22 000uF (0,47uF capacity it does not measure, 1uF do)
ESR: 10 - 20 000mOhms (all bellow 10mOhms is shown as 0,00Ohms)
Measure at frequency 100kHz
It can determine, when cap is leaky and therefore bad (In-Circuit/Leaky message)
It does calibrate it's electrodes, so it can measure ESR of the cap in as low values, as 0,01 Ohms


So I looked at my pile of caps:

...and tried it to see, what can I expect from the caps:

Vent 3300uF 10V from Enermax 620W Liberty PSU, desoldered after 5 years of usage:

3494uF 10mOhms - surprising!

Hitachi HP3 390uF 400V from Enermax 620W Liberty PSU, desoldered after 5 years of usage:

357.4uF 180mOhms - pretty solid

New Panasonic TS-ED 470uF 400V

405.4uF 140mOhmů (uhm... 400V caps is probably not really measurable well at 100kHz and low voltage...)

New Samxon URL 1000uF 6.3V polymer

1134uF and under 10mOhms ESR

New Samxon URL 470uF 16V polymer

477uF 10mOhms ESR

New Samxon RS 47uF 35V

49.89uF 250mOhms (classic RS cap)

New Samxon GK 220uF 25V

210.8uF 60mOhms (for first time used after like 4+ years in the bag it reported that the cap is leaky... on second try it started working again well)

New Nichicon LE 820uF 2.5V polymer

777.8uF and under 10mOhms ESR (capacity is little disappointing to me)

New Sanyo SVP 180uF 16V polymer

189.7uF 20mOhms (a little bigger ESR for polymer...)

New Panasonic FM 3300uF 16V

3473uF 20mOhms

New Samxon GC 3300uF 6.3V

3439uF and under 10mOhms ESR

New Samxon GA 3300uF 6.3V

4435uF and under 10mOhms ESR

Vent 3300uF 16V from Enermax 620W Liberty PSU, desoldered after 5 years of usage:

3296uF 10mOhms - very surprising!

New Samxon GK 220uF 16V

209.9uF 40mOhms (and this one worked on the first try)

New Samxon RL 4.7uF 50V

4.5uF 1150mOhms (how lower can I go?)

New Samxon GK 47uF 25V

45.86uF 220mOhms

New Samxon RL 1uF 50V

0.99uF 1850mOhms (so well, 1uF is possible to measure, 0.47uF caps are not measurable )


Surprise is the very good parameters of the Vent caps, desoldered from old Enermax PSU and the high overcapacity in the GA cap.


What all this will could interest others? Well, I can measure any cap for you
Of course it need to be shipped to me, but I can measure not only the capacity, but the ESR too, so we can see and compare, how bad the cap are. No returns are realisticaly expectable, tough. Surely no-one want to store or even return bad caps, huh?
Address will be sendt in PM for these who would like to know - postage cost of evenlope from Australia to Czech republic was $3.5 AUD, so it is not that bad

[brethin]

Re: Measuring caps

No device can measure true ESR of a cap in circuit unless the cap is in series (alone) in the circuit which is never the case for the most part for what most people want to test.

[Pinhead]

Re: Measuring caps

This is definitely interesting, as I have been looking into banks of supercapacitors for the ultimate filter caps and was curious how the ESR compared. My bank of 6F 2.7v supercapacitors are rated at 80mohm ESR each, for a total of 560mohm/18.9v. It would seem that the ESR is too high for such an application.

"Low ESR" is anything below what value? I know this figure differs between manufacturers but what is the consensus on the forum?

[mariushm]

Re: Measuring caps

Polymer capacitors can have as low as 4-5 mOhm ESR. Tantalum and ceramic capacitors CAN have lower ESR but it depends on manufacturer, series etc.

At those low ESR values, even the length of the leads on the capacitor affect the ESR value. I see you measured the capacitors putting the probes at the end of the leads which is not good.

When using a proper LCR meter, you MUST put leads of your LCR meter as close as possible to the base of the capacitor.

Next, this Peak ESR meter is not a proper LCR meter so don't think it's accurate enough to measure ultra low esr values. It actually doesn't even measure the ESR, but a component of it, which just happens to be the predominant part at high frequencies so the other parts can be ignored.

The lowest I would believe that meter to be able to measure with a reasonable accuracy is maybe 15-20 mOhm. That's good enough for repairing hardware.

Other cheap ESR meters like Blue ESR or ESR micro will not be any better but at that price, but at least esr micro isn't close to $100 or more (I paid about $60 for mine).

Nowadays, you can get a proper LCR meter for about $100 if you're OK with a maximum of 10kHz, or a proper 100kHz LCR meter with 100kHz measurement for about $170.
When I see PeakESR sold for about $130.. it makes me sad.

[tmiha71]

Re: Measuring caps

What is the value of measuring current ?

If it is too low, battery powered, then you have unspecified error, which depends on leakage current of capacitor.

For Suncon ME-WG (had data sheet handy) , leakage current is 0.03xCxV,
so for example, for cap 3300uF 16V leakage current is 3300x16 = 1584uA, or 1,5 mA.

If measurement current is 5mA (saw some other ESR meters have that value), then error is ~30% (in capacitance and in ESR), if it's lower (measuring current) than it's even worse...

For polymer caps, leakage current is 0.2xCxV, so situation is even worseer...
where C is capacitance in uF, and V is rated voltage, resulting in current in mikro Amperes...
Also LC (leakage current) is specified (in datasheets) after 2min, after voltage, and current are applied (not clear if that current is ripple current)...
To minimize influence of leakage current, measuring current should be at least 50x leakage current to get 2% error...

For this instrument capacitors with high CxV could be very problematic....