? on old electrolytic caps

D

Dave

Guest
I have an LCR meter which shows the ESR for electrolytic caps, but I have no
idea how to interpret this number. How do you know if a cap is shorted or
boardering on that status? I mean, if it gives me a reading of zero Ohms,
that's obvious, but what if a small (4.7uF), medium voltage (35V) cap comes
up with a reading of, say, 3 Ohms? Is that too low, like I expect, or
should it be considered acceptable? I just don't know what a good cap would
likely register, and have been surprised in the past when a brand new cap
registered a lower ESR than the one I thought was bad. Where can I find
info on the subject? Any ideas are welcome.

Thanks...

Dave
 
On Tue, 17 Jun 2014 16:50:40 -0500, "Dave" <db5151@hotmail.com> wrote:

I have an LCR meter which shows the ESR for electrolytic caps, but I have no
idea how to interpret this number. How do you know if a cap is shorted or
boardering on that status? I mean, if it gives me a reading of zero Ohms,
that's obvious, but what if a small (4.7uF), medium voltage (35V) cap comes
up with a reading of, say, 3 Ohms? Is that too low, like I expect, or
should it be considered acceptable? I just don't know what a good cap would
likely register, and have been surprised in the past when a brand new cap
registered a lower ESR than the one I thought was bad. Where can I find
info on the subject? Any ideas are welcome.

Thanks...

Dave
Click to expand...

In ESR, low is good. But 0 ohms could be shorted. It's easy to check
for a short other ways.

3 ohms for the 4.7u sounds perhaps a little high, but might be OK;
maybe it was old and getting dry. A new one could well be lower.

Check some cap data sheets for max or typical ESRs. Really big
aluminum caps, or polymer aluminums, can be milliohms.


--

John Larkin Highland Technology, Inc

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On Tue, 17 Jun 2014, Dave wrote:

I have an LCR meter which shows the ESR for electrolytic caps, but I have no
idea how to interpret this number. How do you know if a cap is shorted or
boardering on that status? I mean, if it gives me a reading of zero Ohms,
that's obvious, but what if a small (4.7uF), medium voltage (35V) cap comes
up with a reading of, say, 3 Ohms? Is that too low, like I expect, or
should it be considered acceptable? I just don't know what a good cap would
likely register, and have been surprised in the past when a brand new cap
registered a lower ESR than the one I thought was bad. Where can I find
info on the subject? Any ideas are welcome.
Click to expand...
Practice, practice, practice. Try all the electrolytics you have on hand,
try some in-curcuit (assuming the unit tests in-circuit), buy some new
ones and see. Try to get a feel.

Keep bringing home junk from the garbage that will likely have bad caps,
like LCD monitors. Once you find some bulging capacitors, which are bound
to be bad, test those and see.

This will give you a feel for what's good and what's bad.

Michael
 
"Dave"
>I have an LCR meter which shows the ESR for electrolytic caps,

** Make and model please.

> but I have no idea how to interpret this number.

** As with any measurement, you must know what to expect or it is
meaningless to you.


> How do you know if a cap is shorted or boardering on that status?

** Use an ohm meter.

The reading should be tens or hundreds of thousands of ohms.


I just don't know what a good cap would likely register, and have been
surprised in the past when a brand new cap registered a lower ESR than the
one I thought was bad.
Click to expand...

** You are way off the game.

The lower the ESR reading, the better.


Where can I find info on the subject?
Click to expand...

** Even in old equipment, most electros are still fine so take note of the
readings you get and make a list with varying values and voltages and the
corresponding ESR.

Make sure to post the details of your LCR meter - cos not all work the
same.



..... Phil
 
On Wed, 18 Jun 2014 14:38:55 +1000, "Phil Allison" <phil_a@tpg.com.au> wrote:

"Dave"
I have an LCR meter which shows the ESR for electrolytic caps,

** Make and model please.

but I have no idea how to interpret this number.

** As with any measurement, you must know what to expect or it is
meaningless to you.


How do you know if a cap is shorted or boardering on that status?

** Use an ohm meter.

The reading should be tens or hundreds of thousands of ohms.
Click to expand...

One fun thing about electrolytic caps is that they store and even generate
voltages, through dielectric absorption and electrochemical effects. That can
really fool a DVM on its ohms range, especially if you let it auto-range.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
 
"John Larkin"
"Phil Allison"

"Dave"
I have an LCR meter which shows the ESR for electrolytic caps,

** Make and model please.

but I have no idea how to interpret this number.

** As with any measurement, you must know what to expect or it is
meaningless to you.


How do you know if a cap is shorted or boardering on that status?

** Use an ohm meter.

The reading should be tens or hundreds of thousands of ohms.

One fun thing about electrolytic caps is that they store and even generate
voltages, through dielectric absorption and electrochemical effects. That
can
really fool a DVM on its ohms range, especially if you let it auto-range.
Click to expand...

** Quite so.

FYI: by "ohm meter" I meant an analogue one, ie a moving coil
multimeter. In any case, a shorted electro would show up on a
DMM quite reliably.

The OP is asking the impossible cos verifying some old electro
is still OK requires a bank of tests, meters and PSUs.

Where possible, after doing an ESR test, I just switch old equipment
on and watch out for smoke.

Anecdote:
-----------

I had a new in box power amplifier for repair some years back that
insisted on blowing its AC fuse at switch on. However, I found it
could be brought up gradually using a Variac, pulling a large AC
current if done too fast.

Made in Germany it used a pair chassis mount, 30mF, 100V Siemens
electros in the PSU - the kind with 5mm bolts on top.

Both were getting damn hot and even after an hour the Variac was
set not much beyond half mains voltage - so I stopped torturing them.

Turned out, the amplifier had been left in storage for about 2 years
and the electros had depolarised something fierce.


.... Phil
 
<jurb6006@gmail.com>
Actually ESR should be one tenth of Xc or less.
Click to expand...

** Huh ????

This a candidate for "Meaningless Post of the Year" ?

Or is it too dumb ...........


..... Phil
 
On Tue, 17 Jun 2014 16:50:40 -0500, "Dave" <db5151@hotmail.com>
wrote:

I have an LCR meter which shows the ESR for electrolytic caps, but I have no
idea how to interpret this number. How do you know if a cap is shorted or
boardering on that status? I mean, if it gives me a reading of zero Ohms,
that's obvious, but what if a small (4.7uF), medium voltage (35V) cap comes
up with a reading of, say, 3 Ohms? Is that too low, like I expect, or
should it be considered acceptable? I just don't know what a good cap would
likely register, and have been surprised in the past when a brand new cap
registered a lower ESR than the one I thought was bad. Where can I find
info on the subject? Any ideas are welcome.

Thanks...

Dave
Click to expand...

---
The ESR (Equivalent Series Resistance) of a capacitor is the
resistance (_not_ the reactance) it presents to charge trying to
flow into or out of a capacitor, and causes a capacitor to heat up
due to the power dissipated by its internal I˛R losses - generally,
if not always - in the dielectric.

The resistance of a capacitor is an entirely different thing, and
amounts to the leakage current measured through the dielectric with
a voltage across it.

In terms of goodness, the lower the ESR and the higher the
resistance the better.

John Fields
 
>"This a candidate for "Meaningless Post of the Year" ? "

Well I screwed that up royally. Damn send button.
 
In article <b243q9t7gq15ragisjeqisjkn30iib91do@4ax.com>,
jfields@austininstruments.com says...
The resistance of a capacitor is an entirely different thing, and
amounts to the leakage current measured through the dielectric with
a voltage across it.

In terms of goodness, the lower the ESR and the higher the
resistance the better.

John Fields
Click to expand...
Could you please clarify that a bit? I am only an
inbred from Maine and I did quite get that one.

Jamie
 
On Wed, 18 Jun 2014 17:19:49 -0400, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:

In article <b243q9t7gq15ragisjeqisjkn30iib91do@4ax.com>,
jfields@austininstruments.com says...
The resistance of a capacitor is an entirely different thing, and
amounts to the leakage current measured through the dielectric with
a voltage across it.

In terms of goodness, the lower the ESR and the higher the
resistance the better.

John Fields

Could you please clarify that a bit? I am only an
inbred from Maine and I did quite get that one.

Jamie
Click to expand...
Greetings Jamie,
Though I am only a basics electronics kind of guy I do sorta know
this. ESR is Equivalent Series Resistance and plain old resistance is
resistance to the flow of DC. So an ohm meter will measure the
resistance to DC, which should be high. The ESR is not measured with
DC, but with AC. And AC should be able to go through the cap easily
while it should block DC. I think I got that right.
Eric
 
In article <vib4q9pk9a7ei9sdhcpafe8eqpp91qk0tu@4ax.com>,
etpm@whidbey.com says...
On Wed, 18 Jun 2014 17:19:49 -0400, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:

In article <b243q9t7gq15ragisjeqisjkn30iib91do@4ax.com>,
jfields@austininstruments.com says...
The resistance of a capacitor is an entirely different thing, and
amounts to the leakage current measured through the dielectric with
a voltage across it.

In terms of goodness, the lower the ESR and the higher the
resistance the better.

John Fields

Could you please clarify that a bit? I am only an
inbred from Maine and I did quite get that one.

Jamie
Greetings Jamie,
Though I am only a basics electronics kind of guy I do sorta know
this. ESR is Equivalent Series Resistance and plain old resistance is
resistance to the flow of DC. So an ohm meter will measure the
resistance to DC, which should be high. The ESR is not measured with
DC, but with AC. And AC should be able to go through the cap easily
while it should block DC. I think I got that right.
Eric
Click to expand...

You know if "Leakage" resistance was put in the statement, I may have
understood that.:)

Jamie
 
On Wed, 18 Jun 2014 17:19:49 -0400, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:

In article <b243q9t7gq15ragisjeqisjkn30iib91do@4ax.com>,
jfields@austininstruments.com says...
The resistance of a capacitor is an entirely different thing, and
amounts to the leakage current measured through the dielectric with
a voltage across it.

In terms of goodness, the lower the ESR and the higher the
resistance the better.

John Fields

Could you please clarify that a bit? I am only an
inbred from Maine and I did quite get that one.

Jamie
Click to expand...

---
If you did "quite get" it, why is clarification necessary?

John Fields
 
On Wed, 18 Jun 2014 22:24:02 -0400, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:

In article <vib4q9pk9a7ei9sdhcpafe8eqpp91qk0tu@4ax.com>,
etpm@whidbey.com says...

On Wed, 18 Jun 2014 17:19:49 -0400, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:

In article <b243q9t7gq15ragisjeqisjkn30iib91do@4ax.com>,
jfields@austininstruments.com says...
The resistance of a capacitor is an entirely different thing, and
amounts to the leakage current measured through the dielectric with
a voltage across it.

In terms of goodness, the lower the ESR and the higher the
resistance the better.

John Fields

Could you please clarify that a bit? I am only an
inbred from Maine and I did quite get that one.

Jamie
Greetings Jamie,
Though I am only a basics electronics kind of guy I do sorta know
this. ESR is Equivalent Series Resistance and plain old resistance is
resistance to the flow of DC. So an ohm meter will measure the
resistance to DC, which should be high. The ESR is not measured with
DC, but with AC. And AC should be able to go through the cap easily
while it should block DC. I think I got that right.
Eric

You know if "Leakage" resistance was put in the statement, I may have
understood that.:)

Jamie
Click to expand...

---
Doesn't Ohm's law work in Maine?

John Fields
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:si75q9p07h0gqirhan0eigcj3p9nj4ghoo@4ax.com...
On Wed, 18 Jun 2014 17:19:49 -0400, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:

In article <b243q9t7gq15ragisjeqisjkn30iib91do@4ax.com>,
jfields@austininstruments.com says...
The resistance of a capacitor is an entirely different thing, and
amounts to the leakage current measured through the dielectric with
a voltage across it.

In terms of goodness, the lower the ESR and the higher the
resistance the better.

John Fields

Could you please clarify that a bit? I am only an
inbred from Maine and I did quite get that one.

Jamie

---
If you did "quite get" it, why is clarification necessary?

John Fields
Click to expand...

https://www.dropbox.com/s/cijji0j8kllix51/cap.jpg For reference

Rick
 
On 2014-06-18, Phil Allison <phil_a@tpg.com.au> wrote:
jurb6006@gmail.com

Actually ESR should be one tenth of Xc or less.



** Huh ????
Click to expand...

Looks like he was aiming for "Zc" but missed


--
umop apisdn


--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
 
"Jasen Bleats" <jasen@xnet.co.nz>
Phil Allison

jurb6006@gmail.com

Actually ESR should be one tenth of Xc or less.



** Huh ????

Looks like he was aiming for "Zc" but missed
Click to expand...

** Now that is the "Dumbest Post of the Year"

Baaaaaaaaaaaaaaaahhhhhhhhhhhhhh

Plop.



..... Phil
 
Maynard A. Philbrook Jr. <jamie_ka1lpa@charter.net> wrote:
In article <b243q9t7gq15ragisjeqisjkn30iib91do@4ax.com>,
jfields@austininstruments.com says...
The resistance of a capacitor is an entirely different thing, and
amounts to the leakage current measured through the dielectric with
a voltage across it.

In terms of goodness, the lower the ESR and the higher the
resistance the better.

John Fields

Could you please clarify that a bit? I am only an
inbred from Maine and I did quite get that one.
Click to expand...

If you take an electronic device, even something simple like a battery
there are still losses inside the device from the wiring, connections and
other electrochemical stuff going on inside the device.

Those internal losses are what's called ESR. For instance, if you short
out a AAA battery you will get less current than if you short out a D
cell, even though both can in theory output 1.5V. The D cell has beefier
internal construction and offers a lower internal resistance, so more
current can be drawn from it.

The tricky part is a battery, (or capacitor or anything really) is not a
plain resistor, so you can't measure this "equivalent" value with an ohm
meter, but if you could, the result would be the ESR.

In capacitors, you generally want the lowest possible ESR. A cap with a
high ESR is old, failing, cheap or just junk, and it can potentially heat
up during use, just like a resistor. Heat makes electrolytic capacitors
dry up, which increased the ESR, which make them heat up more, until they
explore or just stop being capacitors.
 
On Thu, 19 Jun 2014 17:19:00 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

Maynard A. Philbrook Jr. <jamie_ka1lpa@charter.net> wrote:
In article <b243q9t7gq15ragisjeqisjkn30iib91do@4ax.com>,
jfields@austininstruments.com says...
The resistance of a capacitor is an entirely different thing, and
amounts to the leakage current measured through the dielectric with
a voltage across it.

In terms of goodness, the lower the ESR and the higher the
resistance the better.

John Fields

Could you please clarify that a bit? I am only an
inbred from Maine and I did quite get that one.

If you take an electronic device, even something simple like a battery
there are still losses inside the device from the wiring, connections and
other electrochemical stuff going on inside the device.

Those internal losses are what's called ESR. For instance, if you short
out a AAA battery you will get less current than if you short out a D
cell, even though both can in theory output 1.5V. The D cell has beefier
internal construction and offers a lower internal resistance, so more
current can be drawn from it.

The tricky part is a battery, (or capacitor or anything really) is not a
plain resistor, so you can't measure this "equivalent" value with an ohm
meter, but if you could, the result would be the ESR.

In capacitors, you generally want the lowest possible ESR. A cap with a
high ESR is old, failing, cheap or just junk, and it can potentially heat
up during use, just like a resistor. Heat makes electrolytic capacitors
dry up, which increased the ESR, which make them heat up more, until they
explore or just stop being capacitors.
Click to expand...

---
Right.

They turn into explorers. ;)

John Fields
 
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