Re: ESR Meter - design contest

On Sun, 15 Jul 2007 00:34:54 -0500, the renowned Spehro Pefhany
<speffSNIP@xxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Sat, 14 Jul 2007 11:39:16 -0700, the renowned John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Sat, 14 Jul 2007 14:06:40 -0500, Spehro Pefhany
<speffSNIP@xxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Sat, 14 Jul 2007 10:07:11 -0700, the renowned John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Sat, 14 Jul 2007 07:53:56 -0700, Winfield <winfieldhill@xxxxxxxxx>
wrote:

Fred Bloggs wrote:
John Larkin wrote:
Fred Bloggs wrote:
John Larkin wrote:
Fred Bloggs wrote:
John Larkin wrote:

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.

Granted they are amateurish junk, but your designs and ideas
are so *ugly* they are borderline grotesque. When you have
something artful to suggest that will be the day....

You don't approve of my products? Show us some of yours.

As they say, I don't have to be a chef to know the food stinks...

Show us something you've designed.

You show us an esr meter that doesn't require a VMX crate.

I suggest we have an esr-meter design contest. However, to
make it usenet friendly, and accessible to the readers, all
entries must be made in ASCII drawings, annotated with text.

Why not make it a group project, for real? I'd be willing to do the
first cut at schematic and algorithms. What we really need is someone
to hack the real code; I hate to program, and I'm going to do it most
of the weekend likely [1], so I'm not going to volunteer for that
part!

I'll volunteer, on provision that you, and anyone else contemplating a
serious contribution, read a few things so as to understand the
problem domain (testing, and in particular in-circuit testing of
e-caps) better.

It looks logical that it would be your task to do that research and
post a concise summary of requirements.

John

Well, the problem is that there's a dichotomy (or maybe a trichotomy)
in the wish lists.

First we have the service tech's unit:

- range up to 10 or 100 ohms with 0.01 resolution
- measurement frequency the equivalent of 100kHz
- no need to distinguish between impedance and ESR
- accuracy is of little importance, 10% is more than good enough,
we are looking for order of magnitude changes
- must be able to measure in-circuit, and preferably without
concern about polarity, so voltage should be low (say < 200mV) and
current should be 50-100mA RMS maximum.
- two wire probe is probably all that's practical, we have to beat
the convenience of tacking a known-good cap across the part and
trying it out
- it's reasonable to expect the meter to survive connection to a large
capacitor charged to ~400VDC without complaint
- should be simple/cheap/reliable/rugged and easy to use
- a "Pike" model is possible that would analyze the cap and deliver
a go/no-go indication (or possibly two for low-Z and regular caps)

(oops, I guess ^N with the wrong window in focus will do that)

Then we have the SMPS designer's unit:

- 0.001 ohm resolution
- reasonable accuracy (say 1% or better)
- must measure actual ESR
- able to measure relatively low value ceramic caps as well
as e-caps
- Kelvin measurement
- variable frequency measurement (maybe 100Hz to 1MHz)
- milliohmmeter for inductors
- no need for in-circuit but should not be damaged by cap
charged to ~50V
- reasonable cost


and hey, if we're dreaming

- complex and real impedance of inductors, resistors and caps over
that range
- ditto with DC bias on capacitors 0-10V and current on inductors
0-2A


Ideally, perhaps, kind of like a low-accuracy version of this guy:
http://cp.literature.agilent.com/litweb/pdf/5989-4435EN.pdf


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@xxxxxxxxxxxx Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
.

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