ESR Meter Recommendations

W2HX w2hx at
Wed Sep 30 05:39:49 CDT 2015

Just to clarify a little more (at the risk of being explaining things everyone already knows)...

In an ideal capacitor, after the capacitor has charged, all DC current is blocked. However, when applying a DC voltage to a real capacitor, some small current will continue to flow as electrons pass through the dielectric because the dielectric is not ideal.  So to model this using ideal components, we show a resistor in parallel to the capacitor that represents the amount of current that continues to flow even though the capacitor is supposed to be blocking. This modeled parallel resistor represents the leakage current. In this case, it is important to test at the working voltage of the circuit (which is usually lower than the working voltage of the capacitor itself with some margin of safety).  This is because the current through a resistor is dependent on the voltage across it.

Now, at AC, a capacitor will pass current and lead the voltage across it.  In an ideal capacitor, no power would be dissipated.  However, because it is not ideal, some power is dissipated. This dissipated power is represented by a series resistance.  Because an idealized circuit with a cap and a resistor in series will not pass DC current, this circuit must be tested at AC.  And the most accurate result will be achieved at the working frequency of the circuit, again, typically 120 Hz (or 2xline frequency).

I hope this helps someone

-----Original Message-----
From: cctalk [mailto:cctalk-bounces at] On Behalf Of W2HX
Sent: Wednesday, September 30, 2015 8:10 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: ESR Meter Recommendations

It seems you may be using two terms interchangeably that have different meanings. Leakage is parallel resistance  (DC) and ESR is series resistance (actually impedance so it is frequency dependent. Typically 120 Hz with a full wave bridge rectifier in front of it). 

-----Original Message-----
From: cctalk [mailto:cctalk-bounces at] On Behalf Of drlegendre .
Sent: Wednesday, September 30, 2015 12:11 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: ESR Meter Recommendations


I have two of the Atmega328 uC based 'swissknife' testers you mention, cost about $25 ea. on eBay, and have been exceptionally happy with them. They're a brilliant little piece of instrumentation, and IMHO no electronics hobbyist should be without one. For quick testing & ID of SS components, they're just the ticket.

Secondly, I have one of these units: - "Capacitor Wizard". They are also quite useful, and have some nice features like a quick-reading analog scale and audible indicator allowing you to set an ESR threshold and then test eyes-off the meter. This can be a real safety measure, if you're working deep inside a chassis. They are a bit overpriced for what you get, though, IMHO.

If you're mainly interested in testing for leakage in caps, and want to test them +at+ real working voltages, then you need a device like a Heathkit IT-28 or its Eico / Paco equivalent. Note that these are all "LCR bridges" with leakage test as an added feature. The Heath unit goes to 600V DC, not sure of the others.

Finally, there are the "in circuit capacitor checkers" made by Paco and possibly Heath / Eico. These are semi-useful, but in reality, they are pretty dang obsolete - and for some reason, folks pay a lot for them on eBay.. no idea why. Thing is, to really peg down any ESR trouble, you always need to disconnect one end anyway (in case of circuit loading or other fault) - so what's the real value of "in circuit" in that case?


On Tue, Sep 29, 2015 at 5:34 PM, TeoZ <teoz at> wrote:

> Never used one on a power supply but for motherboard capacitors and 
> misc parts they work fine. For the price they are worth having around.
> -----Original Message----- From: Ken Seefried
> Sent: Tuesday, September 29, 2015 5:24 PM
> To: cctalk at
> Subject: ESR Meter Recommendations
> I'm going to be working on my 11/730s power supply, so I'm in the 
> market for an ESR meter.  I've seen some (older) recommendations for 
> the AnaTek 'Blue' and various 'Dick Smith' derivatives.  However, eBay 
> is flooded with knockoff Mega328 based ESR/Transistor/SCR/etc. testers 
> all looking like:
> dp/B00NKY3M1W/ref=sr_1_16?ie=UTF8&qid=1443561246&sr=8-16&keywords=esr+
> meter
> Anyone had any experience with one of these devices?
> KJ
> ---
> This email has been checked for viruses by Avast antivirus software.

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