"Jeff Liebermann"


If you have 1 volt of output swing, and an assumed function generator
output impedance of 50 ohms, the short circuit current will be about
20ma. Shove that into a 0.5 ohm electrolytic cazapitor, and you'll
measure maybe 10mv across the cazapitor. That's kinda hard to see.

** What kind of POS scope do you have ???

10mV rms = 28.3 mV p-p.

My scope goes down to 5mV per division - then has a 5X mag switch if
needed.

Of
course you could supply more than 1 volt but then you will have some
problems trying to use this technique without removing the cazapitor
from the PCB.

** Utter ******** !!!

As your own example proves.


For what it's worth, I did it this way until I bought an ESR meter.
Later, I decided to actually measure the output impedance of my
function generator. The data sheet said 50/75 ohms, but it was
anywhere between 30 and 100 ohms depending on the position of the dial
and output step attenuator.

** Just set it to max and that's it for ESR testing.


If you look carefully at the schematics supplied below, most of them
put a known series resistance at the output of the generator section
to the cazapitor. You could do the same thing with the function
generator. 100 ohms in series with an alleged 50 ohms will not
magically make the method more accurate, but it will reduce the error
to a tolerable level.

** More ********.

The vast majority of electros have less than 1 ohm ESR values - so any
error in the calculated drive current is TINY in comparison to a 50 ohm
source.

The variation in ESR values between new electros of the same type is far
more.


..... Phil