On Fri, 10 Jul 2015 22:17:55 -0700 (PDT), Phil Allison
wrote:
Jeff Liebermann wrote:
All work quite well. I mostly use the Capacitor Wizard because the
meter reading is faster than the digital variety, that requires
shorting the leads to zero the display (to remove test cable
resistance from the measurement).
** How absurdly lazy, zeroing only takes one or two seconds
and does not need to be repeated unless the meter is switched off.
All ESR readings are virtually instantaneous after that.
The banana or pin jacks found on some ESR meters, including my Dick
Smith K-7204, do not make a reliable connection. The associated
probes are not much better. If I move the leads, I'll see some
variations in reading from the change in lead resistance. However,
you're correct about me being lazy. I should have soldered the jacks
and the probes long ago. (Added to things to do list for today).
If the cap is being tested out of circuit, no leads are normally needed.
I do test caps out of the circuit, but only after I've unsoldered them
from the PCB. That's to verify that they really were bad. Other than
that, I rarely measure individual components, except when the markings
have disappeared. 2 of my 3 ESR meters have soldered leads. It will
shortly be 3 of 3 making measurements without test leads impossible.
However, this meter is not terribly accurate below about 1 ohm.
Good enough for testing electrolytic capacitors,
** No it isn't.
The ESR of most electros of over 1000uF is under 0.05 ohms.
It can become a problem with the Cap Wizard at 100 uF.
See the manual at:
http://midwestdevices.com/_pdfs/Capmanual9.pdf
See the table of "Capacitor Types and Expected ESR - 1uf & up"
For 1 uF and up, they consider anything less than 3 ohms as good.
However, you're correct. When I measure a BFC (big fat capacitor),
usually in a power supply, a digital meter is needed. I use this
chart for reference:
http://802.11junk.com/jeffl/crud/ESR.txt
There's also some interesting stuff in the Cap Wizard manual on
measurements with parallel inductance and resistance.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558