Where are all the ESR meters?

[Michael A. Terrell]

Just use a spring return spdt toggle.
Toggle to test.

Ckt ---o
o<--o---- to DUT
|
Gnd ---+-------- to DUT

Good idea for some applications, but how are you going to maintain
contact resistance? We are talking about readings of hundreds or
thousandth of an ohm.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Robert Baer]

How many 200 KV Electrolytics have you seen?

Not electrolytics..use the old-fashioned power line caps (not exactly
light).

 

[Robert Baer]

Perhaps a better question is, how big is big?

Several designs we've been considering have a
pair of diodes to discharge the test capacitor
and limit the circuit voltages, but I've heard
these can fail with large, charged capacitors.

I think the issue isn't necessarily how high
the voltage (tube amplifiers get to hundreds
of volts), or how high the current delivered,
but how much energy is going to be dissipated
in the protection components that discharge
the guilty capacitor.

I'd say the answer is, the size of two fists.
I think we're talking about ~ 100J of energy.
Isn't that more than enough to blow out a
common glass diode and/or a 1/4-watt resistor?

...by at least a few orders of magnitude!

 

[Terry Given]

Good idea for some applications, but how are you going to maintain
contact resistance? We are talking about readings of hundreds or
thousandth of an ohm.

by doing this:

Ckt ---------+
o |
o<--o-+-- to DUT
|
Gnd ---+-------- to DUT

Cheers
Terry

 

[John Devereux]

by doing this:

Ckt ---------+
o |
o<--o-+-- to DUT
|
Gnd ---+-------- to DUT

Maybe a power resistor in there so it doesn't go bang when you short
out that 400V electrolytic.

 

[Michael A. Terrell]

Not electrolytics..use the old-fashioned power line caps (not exactly
light).

Why would you expect the ESR to change in those type of capacitors?
Any defect in the inner connections would be obvious, because the cap
would disintegrate.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Michael A. Terrell]

by doing this:

Ckt ---------+
o |
o<--o-+-- to DUT
|
Gnd ---+-------- to DUT

So, you want to flash the silver off the contacts to metalize the
insides of the switch's body, or even weld them together?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Fred Bloggs]

Thanks for the excellent illustration of my point. You are far more
concerned about your ego than you are about the technology. Probably
that explains why you don't design electronics.

I know where you're coming from with that statement and it is not true.
I am far enough along to know for sure whether something will work or
not. All you have thought of so far is measuring the in-phase component
of voltage developed by a current pulse. And your typical white board
brainstorming is largely used for the how and not the what. The idea
within the original Italian hobby circuit was not too bad, the execution
was lacking, and the outputs of interest were sort of compressed, but
the idea of a bridge driven by a reasonably *low* impedance current
source, resulting in short transient recovery from the ESL and limited
peak response, is not bad at all.

 

[Fred Bloggs]

Well, Fred, you claim to be in perfect health, yet you haven't even
submitted a set of specifications for YOUR ESR meter design. On the
other hand, you've already dammed designs of others you hadn't even
seen.


As far as your questioning what my disabilities have to do with
anything proves once again just what a fucking asshole you are. You
have no idea how bad my health is but like everyone else here, your over
inflated ego MAKES you damn everything and everyone in sight.

I'll tell you what. Go buy a cane. Strap 75 pounds on your back and
try to do the usual day to day things you HAVE to do to survive. Cut 15
to 20 weeping sores on your legs, and try to get by on no quality sleep,
at all. I don't really sleep anymore. I pass out from exhaustion. Try to
breathe through several layers of mask so you're always short of breath.
Then exert yourself till you feel faint.

There is no way you can simulate most of the side effects of all the
medications. About the only one you can get close to is to alternate
between Magnesium Citrate and Imodium A-D, several times a day. How
would you like to go from starting the day constipated, with a stool so
hard that your ass bleeds, to diarrhea and back to constipated in a
single day?


If I DON'T take ALL of the medicine I can get some sleep, but both my
blood pressure and blood sugar go sky high. I generally have less than
two hours a day to do anything that requires concentration and/or
exertion, so why waste it on a circuit design I can't afford to build?

I WAS working on a design for a computer interfaced ESR meter to
allow quick go/nogo or incoming inspection testing to read both the
capacitance and ESR, and see if they were in spec, when I lost my job on
Sept. 7th, 2001. I was already so sick I couldn't function, and people
laughed in my face when I applied for work. I was stopped by a cop one
day and accused of being drunk, because I couldn't walk a straight
line. Even walking with the cane, assholes like you do their best to
block my way, or try to knock me down. On punk tried to take my cane,
but soon regretted it because his arm was twisted into a knot behind his
back. he was on his knees, begging me to let go. He had ignored my good
right arm that still works, so I grabbed the other end of the cane and
twisted it, and his arm behind his back and pined him so he couldn't let
go.

I had to wait over two years to get any medical help from the VA.
During that time I lost so much strength that I couldn't walk. Even
though I was eating under 1200 calories a day, I put on over 100 pounds.
I topped out at 297 pounds. So far, I have lost 25 pounds, in the last
two years. Its going to take a long time to ever get close to the
normal 180 pounds I was, before I got sick.

You have no damn idea what its like to be severely disabled and a lot
of fucking nerve. Have you EVER heard of anyone else who got 100%
disability in less than two months? Does that tell your pea brain
anything, at all?

It is more than apparent from your posts that newsgroup is on the whole
a disturbing influence for you and may not be the best thing for your
health. You should abandon it and put that time into a support group.

 

[Winfield]

I know where you're coming from with that statement and it is not true.
I am far enough along to know for sure whether something will work or
not. All you have thought of so far is measuring the in-phase component
of voltage developed by a current pulse. And your typical white board
brainstorming is largely used for the how and not the what. The idea
within the original Italian hobby circuit was not too bad, the execution
was lacking, and the outputs of interest were sort of compressed, but
the idea of a bridge driven by a reasonably *low* impedance current
source, resulting in short transient recovery from the ESL and limited
peak response, is not bad at all.

A better idea, I think, is to use a proper higher-impedance
current source, and drive with a 100kHz sine wave, thereby
greatly reducing the ESL problem, which can otherwise be a
killer for the 1 to 30 milliohm region. Using a sine wave
also means the measured ESR can be compared with laboratory
meter readings. Otherwise, how would one compare sets of
square-wave readings with accurate lab instrument readings?

I'm thinking of using a 2-volt peak sine wave with a 200-ohm
resistor (10mA peak test current) delivered from a rail-to-
rail opamp with a slew rate exceeding say 2V/us. I'll break
the resistor into three parts and add two sets of protection
diodes to the rails. The outermost resistor can be a 100-ohm
10-watt high-thermal-mass part to discharge the capacitors.

 

[Spehro Pefhany]

A better idea, I think, is to use a proper higher-impedance
current source, and drive with a 100kHz sine wave, thereby
greatly reducing the ESL problem, which can otherwise be a
killer for the 1 to 30 milliohm region. Using a sine wave
also means the measured ESR can be compared with laboratory
meter readings. Otherwise, how would one compare sets of
square-wave readings with accurate lab instrument readings?

I'm thinking of using a 2-volt peak sine wave with a 200-ohm

2-volt P-P is too high to do in-circuit testing in all cases as it
could cause Si junctions to conduct. 0.2V or 0.3V would be a lot
better.

resistor (10mA peak test current) delivered from a rail-to-
rail opamp with a slew rate exceeding say 2V/us. I'll break
the resistor into three parts and add two sets of protection
diodes to the rails. The outermost resistor can be a 100-ohm
10-watt high-thermal-mass part to discharge the capacitors.

Some of the designs out there don't bother with discharging the
capacitor- they put a low (and stable) -ESR cap of a few uF in series
with the DUT. That way you have an upper limit on the energy to be
handled (given an upper limit on the voltage of (say) 400VDC or 500VDC
to handle off-line filter caps).


Best regards,
Spehro Pefhany

 

[Winfield]

Well, Fred, you claim to be in perfect health, yet you haven't even
submitted a set of specifications for YOUR ESR meter design. On the
other hand, you've already dammed designs of others you hadn't even
seen.

As far as your questioning what my disabilities have to do with
anything proves once again just what a fucking asshole you are. You
have no idea how bad my health is but like everyone else here, your over
inflated ego MAKES you damn everything and everyone in sight.

I'll tell you what. Go buy a cane. Strap 75 pounds on your back and
try to do the usual day to day things you HAVE to do to survive. Cut 15
to 20 weeping sores on your legs, and try to get by on no quality sleep,
at all. I don't really sleep anymore. I pass out from exhaustion. Try to
breathe through several layers of mask so you're always short of breath.
Then exert yourself till you feel faint.

There is no way you can simulate most of the side effects of all the
medications. About the only one you can get close to is to alternate
between Magnesium Citrate and Imodium A-D, several times a day. How
would you like to go from starting the day constipated, with a stool so
hard that your ass bleeds, to diarrhea and back to constipated in a
single day?

If I DON'T take ALL of the medicine I can get some sleep, but both my
blood pressure and blood sugar go sky high. I generally have less than
two hours a day to do anything that requires concentration and/or
exertion, so why waste it on a circuit design I can't afford to build?

I WAS working on a design for a computer interfaced ESR meter to
allow quick go/nogo or incoming inspection testing to read both the
capacitance and ESR, and see if they were in spec, when I lost my job on
Sept. 7th, 2001. I was already so sick I couldn't function, and people
laughed in my face when I applied for work. I was stopped by a cop one
day and accused of being drunk, because I couldn't walk a straight
line. Even walking with the cane, assholes like you do their best to
block my way, or try to knock me down. On punk tried to take my cane,
but soon regretted it because his arm was twisted into a knot behind his
back. he was on his knees, begging me to let go. He had ignored my good
right arm that still works, so I grabbed the other end of the cane and
twisted it, and his arm behind his back and pined him so he couldn't let
go.

I had to wait over two years to get any medical help from the VA.
During that time I lost so much strength that I couldn't walk. Even
though I was eating under 1200 calories a day, I put on over 100 pounds.
I topped out at 297 pounds. So far, I have lost 25 pounds, in the last
two years. Its going to take a long time to ever get close to the
normal 180 pounds I was, before I got sick.

You have no damn idea what its like to be severely disabled and a lot
of fucking nerve. Have you EVER heard of anyone else who got 100%
disability in less than two months? Does that tell your pea brain
anything, at all?

Michael, I'm sorry to hear your health problems have become
so severe. I was hoping the VA would get you back on track,
but now I wonder if they've diagnosed you properly? Could
it be that at this point you're suffering more from the cure
(medications) than the illness?

 

[MooseFET]

Just use a spring return spdt toggle.
Toggle to test.

Ckt ---o
o<--o---- to DUT
|
Gnd ---+-------- to DUT

If the DUT is a large capacitor charged to several hundred volts, that
would have to be one heck of a switch.

I think it would be far better to make a current source and voltage
preamp that can both withstand several hundred volts.

Neither the current source nor the voltage preamp needs to be super
good they just have to not crosstalk. Assuming we have well regulated
+/- 12V supplies, the current source can be just a rail to rail output
driving a resistor. For a measurement current of 1mA, a 12K resistor
would be required. Assuming we have to withstand 500V, we need a
resistor that can take a 21W pulse.

Operating at 1mA results in about a 1uV measurement requirement. This
would let us use a resistor on the order of 100K on the input of the
preamp without getting swamped with noise.

 

[Winfield]

Right. I know, because I *have* been cranked,
more than once. :-(


I'm not stalling; my paper sketches nicely handle
the protection requirements I posted. Basically
my design is a simplified version of the HP meters
I have, based on the fact that 5% accuracy is good
enough. I've been slowed down a bit by the need to
evaluate single-supply instrumentation amplifiers,
etc. And by my real projects: working on the book,
home projects like my rust-infected Japanese Kerria,
my Honeysuckle arbor, and of course, my Harvard job,
with 1T generators, TEC drivers, -- things like that.

Do some of you readers have a suggestion for a low-
power 5-volt opamp with specs like: 2MHz or higher fT,
2V/us or faster slewing, rail-to-rail output that can
deliver 10mA or more while within 500mv of the rail,
and of course, low cost? Should be easy to find.

How about a low-power low-cost 5V instrumentation amp?

 

[Jim Thompson]

[snip]

A better idea, I think, is to use a proper higher-impedance
current source, and drive with a 100kHz sine wave, thereby
greatly reducing the ESL problem, which can otherwise be a
killer for the 1 to 30 milliohm region. Using a sine wave
also means the measured ESR can be compared with laboratory
meter readings. Otherwise, how would one compare sets of
square-wave readings with accurate lab instrument readings?

I'm with you on that, even the frequency.

I'm thinking of using a 2-volt peak sine wave with a 200-ohm
resistor (10mA peak test current) delivered from a rail-to-
rail opamp with a slew rate exceeding say 2V/us. I'll break
the resistor into three parts and add two sets of protection
diodes to the rails. The outermost resistor can be a 100-ohm
10-watt high-thermal-mass part to discharge the capacitors.

I've been thinking along the lines of an AC _current_source_, and
using the cap UT as the filter to keep it queued. Then you get a
linear reading of ESR.

But I've been lacking time to put pencil to paper... I'm up to my
gills in (paying) projects... and, in my business, one must make money
while it's available ;-)

...Jim Thompson

 

[Jim Thompson]

[snip]

Michael, I'm sorry to hear your health problems have become
so severe. I was hoping the VA would get you back on track,
but now I wonder if they've diagnosed you properly? Could
it be that at this point you're suffering more from the cure
(medications) than the illness?

One has to wonder.

I've been thru all kinds of shit tracing my leg pain to crushed disks,
only to finally have someone say, "Why don't we take an X-ray of your
hip".

Looks like that's the culprit :-(

...Jim Thompson

 

[John Larkin]

2-volt P-P is too high to do in-circuit testing in all cases as it
could cause Si junctions to conduct. 0.2V or 0.3V would be a lot
better.

10 mA won't make much voltage across an electrolytic cap!

Some of the designs out there don't bother with discharging the
capacitor- they put a low (and stable) -ESR cap of a few uF in series
with the DUT. That way you have an upper limit on the energy to be
handled (given an upper limit on the voltage of (say) 400VDC or 500VDC
to handle off-line filter caps).

The other possibility is to just limit the current, not instantly
discharge the cap,

John

 

[John Larkin]

A better idea, I think, is to use a proper higher-impedance
current source, and drive with a 100kHz sine wave, thereby
greatly reducing the ESL problem, which can otherwise be a
killer for the 1 to 30 milliohm region. Using a sine wave
also means the measured ESR can be compared with laboratory
meter readings. Otherwise, how would one compare sets of
square-wave readings with accurate lab instrument readings?

Synchronous detector?

John

 

[Jim Thompson]

Synchronous detector?

John

Without pencil to paper, synchronous _may_ allow separation of real
and imaginary terms.

...Jim Thompson

 

[John Larkin]

I know where you're coming from with that statement and it is not true.
I am far enough along to know for sure whether something will work or
not. All you have thought of so far is measuring the in-phase component
of voltage developed by a current pulse. And your typical white board
brainstorming is largely used for the how and not the what. The idea
within the original Italian hobby circuit was not too bad, the execution
was lacking, and the outputs of interest were sort of compressed, but
the idea of a bridge driven by a reasonably *low* impedance current
source, resulting in short transient recovery from the ESL and limited
peak response, is not bad at all.

If the drive is a sine wave, ESL peaks go away.

And what is a "*low* impedance current source"?

John