On Jan 25, 7:31*am, "Phil Allison" wrote:
"William Sommerwerck"

In other words... If the driving frequency is high enough that the
capacitive reactance is essentially zero, then the net impedance is
essentially the ESR. Right?

** Errr *- *yep.

But it ain't that simple.

One has to examine the actual impedance curves for typical electros to see
what the game is - *the curve is like no other kind of cap.

Think of Q factors of circa 0.05 and ESRs that way exceed the calculated
impedance at 100kHz.

..... *Phil

Nice tip thanks Phil. The 100uF electro's I have came out with ~0.15
ohms of ESR, using your method.
I've never seen an impedance curve for an electro cap. Do you have a
link or know which manufacturer's website I might check?

As a 'silly' rule of thumb it seems that most caps I run across have a
minimum impedance of ~0.1 ohms. (Ignoring the 'resonant' dips that
you sometimes see in the impedance plot.)

George H.