Re: ESR Meter - Roll your own - ESRrev0.JPG

On Fri, 13 Jul 2007 09:47:19 -0400, SP
<speffSNIP@xxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Fri, 13 Jul 2007 06:39:16 -0700, John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Fri, 13 Jul 2007 02:55:14 -0700, Winfield <winfieldhill@xxxxxxxxx>
wrote:

On Jul 12, 4:48 pm, "DaveM" <masondg4...@xxxxxxxxxxxxx> wrote:
"Mike" <nomtrxs...@xxxxxxxxxxx> wrote in message

We'd love to see a copy of the article. Failing that, a posting
of the relevant portion of the meter-reading interpretation and
of the circuit-operation explanation would be helpful. Be sure
to include the author's full names for credit.

Ok, I posted the article on a.b.s.e along with a link to a totally
different meter that was sold by *** Smith electronics. I'd be
interested to hear any comments on the *** Smith version.

The DSE meter was designed by Bob Parker, an aussie with a good head on his
shoulders. The meter has been marketed as both a kit (best bang for the buck)
and fully assembled and tested models. Most service techs that I know and
those that have posted on the sci.electronics.repair NG swear by this meter.
I bought and built a kit a number of years ago, and still use it. It's paid
for itself many times over in the time that I've owned it.

I understand the *** Smith has stopped selling the meter, but Bob has found
other outlets for it. John's Jukes (http://www.flippers.com/) in Canada
sells them (that's where I bought my copy).

I don't think you'll find a bad note from anyone about this meter.

I'd love to have one of those meters. The design seems respectable,
and the most sensitive range, 0.00 to 0.99 ohms, looks ideal for
working with serious switching-supply capacitors. I see it uses a
50mA test current and amplifies the resulting esr signal by about
25x before presenting it to a comparator, the other side of which
gets a slow 20V/ms ramp (9.5uA and 470nF), to measure the signal.

Since lots of single-chip uPs include decent adc's these days, why not
just digitize the voltage drop across the cap? One could then note the
cap charging slope and untangle it from the true esr. And measure
capacitance, for free.

John

Sure,however I think the sensitivity of the typical 10 bit ADC in a
cheap micro is about an order of magntitude too low, so you need a
preamp anyway.

That's about right, but it's still going to be simpler than most of
the goofy and truly terrible "esr" meters we've seen here lately.

You may as well measure leakage and dielectric absorption while you're
at it; code is cheap.

John



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