John Robertson wrote:
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** The Bob Parker ESR meter has an auto-ranging, two digit display that over flows above 99 ohms. It shows ESR values from 0.01 ohms to 99 ohms. The black button zeros the reading before measurements and also cycles the meter on and off.

http://i44.photobucket.com/albums/f9...SCF0045-86.jpg

The "good" 22uF, 500V electros showed readings close to 1.5 ohms while the "bad" ones were completely open. In reality, 2 of the 3 "good" electros were just about to fail open circuit.

Electro caps normally dry out and go high ESR fairly slowly, ones that test perfect one day and go DEAD the next are not playing fair.



I use (and sell) Bob's ESR meter kit (over 600 sold since 1999). The
only improvement I can suggest is to use a regular fixed range digital
ohm-meter in parallel with the leads to be sure the low reading isn't
actually a shorted component.


** Yes, a rare dead short in a capacitor hides its ESR from any meter PLUS caps wired in parallel have a "team ESR" that can hide bad member.


The meter is might also be useful for evaluating lead acid (and other)
batteries...


** Bob's design is most useful for all the common cells and low voltage batteries.

Lithium coin cells ( memory back up) are easily tested for ESR and a high reading means their useful life is nearly over.


..... Phil