ESR (again)

[spec]

Thanks Doc , I did see this design but had parts for build "In stock"
spec, thanks for reform post , I tried it on the 12,000 uF cap ( only 20v) and it would appear OK .

no probs grand. I thought the cap would be OK- they are pretty rugged things.

 

[Nigel Goodwin]

Every one of these meters is called an "LCR meter", and all of them can measure ESR. They can all measure inductance as well.

Obviously they can measure inductance - it's in the name

L (inductance), C (capacitance) and R (resistance).

What it doesn't make clear is that they can measure ESR as well - perhaps they should make the name somewhat clearer, or posters here should.

As I also mentioned, the cheap AVR component testers do all of that anyway, and a great deal more - for almost no cost at all.

 

[Tony Stewart]

So it's NOT just an 'LCR' meter then, it can actually measure ESR as well - which makes it somewhat more useful for finding faulty capacitors.

However, presumably (unlike a proper ESR meter) it can't test them in circuit? (although to be fair there's a small number of circuits where ESR meters can't do that either.

Most ESR meters also tell you the capacitance as well, but not the simple analogue ones like the OP made.

Nigel,
I've had this $250 meter for over 10 years and it has hundreds of useful applications including measuring in-circuit as the voltage with the CC sine wave is usually less than 1 diode drop for isolation from secondary coil resistance.

It's always been called an LCR meter.

But I understand where you are coming from. Even 30 years ago by Philips , Agilent( nee HP) and other makers of these fine instruments, it has always been called an LCR meter.

It wasn't until much later that cheap DMM's tried to offer LCR capability with a much less accurate and cheaper pulse method , which meant they could only measure LCR and not Q, ESR, Df, Rs, Rp etc etc.

regards,
Tony

I come from a Test Engineering and R&D background for 40yrs, so my familiarity with test equipment may be different from others. At one time my capital equipment responsibility included 10 different ATE board testers including ICT and Functional tests where we measured Bode response of servo boards.

 

[spec]

Tony,

Could you recommend a high performance, in production, LCR meter similar to your model- preferably not too expensive. I wouldn't mind building a kit.

spec

 

[MrAl]

Not really, Tony claimed that all you need is an LCR meter to test for faulty electrolytics - which is patently untrue. He later added the extra information that it tests ESR as well. A normal LCR meter wouldn't detect 95+% of faulty electrolytics.

As for home made meters, the now defunkt 'Television' magazine published two designs for them, I used the first type for a number of years.

The frequency you need to use is 100KHz, as that's what the capacitor specs use for testing.

Incidentally, the AVR based component testers from Bangood also test ESR as well as capacitance - with some of the newer versions adding in-circuit ESR testing.

Hi,

So i guess you have used ESR meters that actually help then? If so, that is good to hear. As i always say, i never needed one because i use a scope and wave generator. The scope isnt even very high bandwidth but it is still good enough.

For those of you who want to use a scope and generator, here is a picture of how easy it is to do, and this also illustrates how it can work in-circuit too, because the test voltage can be so low (much less than 0.1v unless the cap is bad, then a little higher as shown).
I post a file like this now and then for those who are interested. This one shows how to interpret the response waveform too.
Note that "Vcap" in the drawing is shown incorrectly, it should be only down to the next point where the straight vertical line part of the response starts, not all the way down to the tip. Little drawing error there, however the ESR vertical line is the most important as that shows the ESR.

 

[granddad]

My LCR only measures LCR !

 

[Nigel Goodwin]

So i guess you have used ESR meters that actually help then? If so, that is good to hear. As i always say, i never needed one because i use a scope and wave generator.

Yes, it's an absolutely invaluable tool for servicing - you 'can' do crude tests with scopes and generators - but the difference is between a small number of seconds and a considerable number of minutes, for a far inferior test

If you've got a scope, then you can look for ripple on the capacitors - you can usually easily clip the scope on the output of the rectifiers, without even removing the board.

 

[Nigel Goodwin]

My LCR only measures LCR ! View attachment 98765

As most do

I've got the same LCR meter, and the ESR meter from the same range - they are designed and built not far from me (and made with PIC's).

 

[MrAl]

Yes, it's an absolutely invaluable tool for servicing - you 'can' do crude tests with scopes and generators - but the difference is between a small number of seconds and a considerable number of minutes, for a far inferior test

If you've got a scope, then you can look for ripple on the capacitors - you can usually easily clip the scope on the output of the rectifiers, without even removing the board.

Hello again,

What is a far inferior test? Certainly not scope and wave generator, as the scope has sensitive inputs, and is calibrated good enough to measure small voltages accurately enough for this kind of test.

You can only check for ripple if the product under test will power up. Both products i had problems with would not power up or power up for less than a second and then shut right down, turning off the power to the caps. In those cases there isnt enough time to look for ripple, although that's a very good idea if the device powers up for at least 5 to 10 seconds or so. I like "power off" tests better anyway though

 

[Tony Stewart]

Tony,

Could you recommend a high performance, in production, LCR meter similar to your model- preferably not too expensive. I wouldn't mind building a kit.

spec

I can only recommend what, I've used. I would never suggest a kit for this, But some may be more aff0rdable now with same or better specs.
Mine supports programmable %tolerance bin sorting , audible beeps, or Go/NoGo, abs/rel., L,C,R with Q,D,Rs, or Rp which is typical. But now support 100kHz in portable and more expensive types to 1MHz and up.

I'm sure you can find a good Japanese design made in Taiwan or CHina now for < $100.

 

[spec]

I can only recommend what, I've used. I would never suggest a kit for this, But some may be more aff0rdable now with same or better specs.
Mine supports programmable %tolerance bin sorting , audible beeps, or Go/NoGo, abs/rel., L,C,R with Q,D,Rs, or Rp which is typical. But now support 100kHz in portable and more expensive types to 1MHz and up.

I'm sure you can find a good Japanese design made in Taiwan or CHina now for < $100.

sounds good- thanks
spec

 

[Nigel Goodwin]

You can only check for ripple if the product under test will power up.

Which is why ESR meters are so useful

It's got to the stage now that there are VERY few repairs coming in at work - and I'm mostly doing deliveries and installations rather than repairs. But up until a couple of years ago I was using the ESR meter multiple times every day, and had done for many years.

As we sell mostly Sony TV's we get very few faulty ones, and as Sony don't use the cheap crap capacitors that others do it does mean ESR meters aren't much use with Sony TV's

However, they do use cheap crap capacitors in sound-bars, and the ESR meter comes in useful for fault finding those.

 

[Tony Stewart]

Thanks Doc , I did see this design but had parts for build "In stock"
spec, thanks for reform post , I tried it on the 12,000 uF cap ( only 20v) and it would appear OK .

For this class of caps....leakage can be defined in worst case for new condition or re-conditioned.

I = .006 √ CV
Not to exceed 6.0 mA max. after 5 minutes, C = Capacitance in µF , V = Rated Voltage, I = Leakage current in mA

Thus after 5 minutes leakage current on 12 mF at say 24Vdc should be < 0.006 * √ ( 0.012 * 24) = 3.2 mA max which is equivalent to 7.5 kΩ minimum across 24Vdc.

Although rarely specified each family of caps has a uniform Rp leakage * C time constant which can be ms to hours for Teflon caps, but in this case 0.09 seconds minimum.
But as noted before Absorption capacitance can have a much longer time constant with high ESR and higher effective parallel resistance.. with time constants in minutes.

The ESR *C also has a relatively constant value in each family of caps which is affected by material, size , temp and rated voltage.

For this class of Cap the ESR*C constant is around 100~200 microseconds. "ultra Low ESR types" would be in the range of 1~10 μs.
So you can expect the ESR of this 12mF cap to be in the range of 15 mΩ give or take a wide margin.

Although an arc strikes on short circuit in picoseconds, it would take couple hundred microseconds to discharge, the residual charge that raises the voltage is due to aging effects of Dielectric Absorption, which doesn't make the cap bad, but does require re-conditioning.

The energy stored would be 1/2CV^2 which at 24V is only 3.5 watt-seconds or Joules

So you could charge up the cap to 24V to 30V and it could power a string of 6 White LEDs or ~18V and with 6 to 12V drop use 300Ω and get 20 to 40mA peak current dropping to dim in about 5 seconds then run on a few mA for much longer.

Does that help?

 

[The Electrician]

Obviously they can measure inductance - it's in the name

L (inductance), C (capacitance) and R (resistance).

My point in emphasizing that is because if a person wants to measure ESR of capacitors and buys a modern "LCR meter", he gets the ability to measure inductance as well. If he buys or builds a special purpose "ESR meter" it most likely can't measure inductance.

What it doesn't make clear is that they can measure ESR as well - perhaps they should make the name somewhat clearer, or posters here should.

It's generally known by people who need an LCR meter and who have studied the specs of modern LCR meters (as they progress toward their purchase decision) that modern LCR meters can measure Rs of a capacitor (also known as ESR).

eBay offerings sometimes give full specs, but I think it's assumed that a potential buyer of those instruments will already know the specs of a particular instrument (easily found at the manufacturer's site) and is perusing eBay because he wants a good price.

As far as what posters here should do, I made it quite clear that all the instruments on eBay I linked to can measure ESR. Since they are modern full-featured meters, they designate the measurement of equivalent series resistance as Rs, rather than ESR. Modern LCR meters are essentially impedance meters, and it's a convention to designate the resistive part of impedance as Rs (in series equivalent mode) or Rp (in parallel equivalent mode). The resistive part of the series equivalent impedance, Rs, is also called ESR when the component being measured is a capacitor.

Pulse or square wave excitation is used by the Peak Atlas and Banggood style ESR meters and the DIY designs found on the web. This doesn't matter for troubleshooting purposes where the goal is to detect a bad electrolytic. But it is not the method used by the capacitor manufacturers to characterize their capacitors at 100 kHz--they use a high-end impedance analyzer (or LCR meter) which makes the measurement with sine wave excitation.

So, a repair technician can use a special purpose ESR meter to detect bad electrolytics, but those meters have limitations that make them unsuitable for design engineering purposes. For example, they can't measure ESR of low value capacitors, and they only measure at one frequency.

I have an Atlas ESR70 which is probably the easiest meter to use for detecting bad electrolytics when I'm in repair tech mode. But I also have LCR meters and impedance analyzers which I use when I need to characterize capacitors and high frequency magnetics for switching power supply design. If I were a hobbyist and could only afford one meter, I would choose a DE-5000 because it can measure ESR at 100 kHz just like the special purpose ESR meters. It can also measure DF at 120 Hz, which is a common specification for electrolytics used in grid frequency power supplies; the special purpose ESR meters can't do this.

 

[The Electrician]

As most do

I've got the same LCR meter, and the ESR meter from the same range - they are designed and built not far from me (and made with PIC's).

I think if you check current offerings you will find that it's not true that "most" only measure L, C and R. Of course, I suppose the truth of that assertion depends on what one means by "most". If "most" is taken to mean "more than half", just using eBay as the place to check offerings I find that "most" meters called "LCR meters" can also measure Q, ESR, Df, Rs, Rp.

As Tony Stewart said "It wasn't until much later that cheap DMM's tried to offer LCR capability with a much less accurate and cheaper pulse method , which meant they could only measure LCR and not Q, ESR, Df, Rs, Rp etc etc".

That was the state of affairs quite some time ago, but now it's the rare meter called an "LCR meter" that only measures L, C and R. Things have changed with the availability of low cost MCUs and custom ICs.

 

[The Electrician]

Tony,

Could you recommend a high performance, in production, LCR meter similar to your model- preferably not too expensive. I wouldn't mind building a kit.

spec

This one: https://www.ebay.com/itm/DER-EE-DE-...502152?hash=item3ac0f6c9c8:g:p~cAAOSwHPlWeWrX

is available for low cost (under US$100), and for more money specialized test leads are available. Search for DE-5000 on eBay.

This meter is the preferred one for hobbyists on a number of forums. Just make sure you don't connect a charged capacitor to it!

 

[spec]

This one: https://www.ebay.com/itm/DER-EE-DE-...502152?hash=item3ac0f6c9c8:g:p~cAAOSwHPlWeWrX

is available for low cost (under US$100), and for more money specialized test leads are available. Search for DE-5000 on eBay.

This meter is the preferred one for hobbyists on a number of forums. Just make sure you don't connect a charged capacitor to it!

Looks good Electrician- many thanks.

UPDATE 2016_04_08 Wow- had a chance to read the specification and some of the reviews/comments on the net- looks like an excellent machine, and for around £100 UK too.

spec

 

[dr pepper]

I have a cheap chinese component tester with a 256x64 display, it shows esr for caps.
It never really gets used, the user interface is annoying.

 

[MrAl]

Which is why ESR meters are so useful

It's got to the stage now that there are VERY few repairs coming in at work - and I'm mostly doing deliveries and installations rather than repairs. But up until a couple of years ago I was using the ESR meter multiple times every day, and had done for many years.

As we sell mostly Sony TV's we get very few faulty ones, and as Sony don't use the cheap crap capacitors that others do it does mean ESR meters aren't much use with Sony TV's

However, they do use cheap crap capacitors in sound-bars, and the ESR meter comes in useful for fault finding those.

Hi again,

It is nice to know that you have used an ESR meter for a long time and found it to work, at least i know now that there are at least some that work good.

Rhetorical: Could it be that the people who make the cheap caps also make the ESR meters? Making cheap caps would open the market for expensive ESR meters (har har)

You gave me an idea through all this. Since i am looking to (possibly) build a hardware based PC hardware monitor (not software) perhaps i can incorporate an AC measurement with the standard DC measurement. Measuring the +12v line is not too hard with a modern microcontroller chip, and that would provide the DC reading which is good to know especially with high current draw devices inside, but that doesnt tell us much about the ripple which as you stated tells us about the health of the capacitor(s) used to filter that 12v line. Measuring the AC and displaying that would tell us how the cap(s) is/are doing over time. If the AC was 0.050v in January and 0.100v in January of the next year, we know something about the power filtering is changing and is most likely the caps.
Now i am starting to lean toward making my own and doing this measurement too. Thanks for the idea

 

[Tony Stewart]

Precision RLC meters generate a constant current source at a precise frequency to measure voltage amplitude and phase shift with 16 bit resolution to determine the real (ESR) and imaginary (uF) from the phase vector (phasor) and then any result can be computed.

Inexpensive RLC DMM's use an integrate and dump method and measure the pulse width over the relatively linear 1/3 beginning of the ramp and repeat with frequency counts.

Murata explain that their MLCC ceramic caps will increase in capacitance with voltage swing. This can affect the apparent ESR and apparent capacitance on all meters as lower results may occur with higher frequencies if the voltage swing detected is lower. The supplier detailed specs need to be consulted in detail to understand disparities in meter readings.

https://www.murata.com/en-global/support/faqs/products/capacitor/mlcc/char/0041