ESR Meter confusion

** Ooopps - that should be higher at LOW frequencies.

Has something to do with losses associated with ions vibrating in sympathy with lower frequencies.

.... Phil

Reply to
Phil Allison
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I built the Cyril Bateman design Tan-theta meter from Electronics World UK articles circa 1999. Very good gear! That isn't strictly Esr as it really displays Esr/Xc which he said was a better figure of merit. It uses a test signal at 100Hz - I think for the very reason you mentioned.

piglet

Reply to
piglet

It's displaying dissipation factor. DF = ESR / Xc There's also loss tangent angle and Q:

Some ESR meters offer a range of test frequencies:

100 Hz, 120 Hz, 1 kHz, 10 kHz, and 100 kHz for the 886 model.

Looking at various capacitor data sheets, I see ESR typically specified at 100KHz, while DF is specified at 120Hz. For high value electrolytics used in switching power supplies, ESR is probably good enough. For 60Hz or 120Hz AC powered motors and linear power supply electrolytics, dissipation factor or loss tangent seems more appropriate.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

I don't know the chemistry involved, but methinks it has more to do with the ratio of the purely resistive component (ESR) to the capacitive reactance (Xc) of the capacitor. The typical ESR meter is actually displaying the vector sum of the resitive and reactive components.

Using high frequencies to measure small value capacitors doesn't work so well. For example, this is the ESR vs Temp graph for a 0.22uf 50v electrolytic: It doesn't show much of a change in measured ESR because what it's actually measuring is the change in Xc (capacitance value) and not the lossy resistive value. The resistive part changes radically with temperature, while the reactive part changes very little, resulting in a fairly flat curve. If I had been able to separate the resistive from the capacitive components, the resistive part would have looked more like the larger value capacitors, such as this 1000uf 6.3VDC:

This can be shown on the revised chart on the Bob Parker ESR meter: Notice that there are XXX markers in the low value (upper left) and small ESR value (lower right) where the readings are questionable. The low values are a problem because of the aformentioned problem of the meter measuring Xc instead of the resistive ESR. The lower right problem is where the indicated ESR is too small for the meter to read accurately. I ran into that with this graph: where the ESR dutifully dropped with temperature, but only down to

0.03 ohms where it flat lined.
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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

** Nope. Electro cap manufacturers actually specify the max ripple current as being lower for 100/120 Hz operation as compared to 20kHz or 100kHz. This is on the basis of self heating so is real dissipation of heat.
** Electro makers do not use low cost ESR meters intended for servicing work.

Very likely they measure internal temp rise with a thermocouple probe under varying ripple current and frequency conditions.

** Yes, equating measured impedance with ESR is only 100% valid in the flat part of a electro cap's impedance / frequency curve. Most electros show a broad flat impedance dip in the high audio to supersonic region on account of their very low Q factors.

.... Phil

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Phil Allison

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.... Phil

Reply to
Phil Allison

Phil Allison:

** Hi Bob,

you sure started something when you persuaded JR to publish that neat little meter of yours. I recall you saying he felt there would not be very much interest in such a device .....

Now, the very mention of "ESR" is like waving a red flag at a bull.

.... Phil

Reply to
Phil Allison

For sure! As JR used to say, "You just never know which projects will be popular and which ones won't". If anyone told me back in 1996 that kits for the ESR meter were still going to be produced and sold nearly 23 years later, I'd have told them they were dreaming. Ya just never know...

Reply to
Bob Parker

Phil, I hope you aren't meaning me, though, when you say JR (pawing the ground). I am not to blame for the success of these kits, I just enjoy supporting good products!

Bob got his real start with the electronic magazines (EA if I recall correctly) down under and Dick Smith (Fiona was my sales rep, a very nice lady!) - which was where I found his kits so many years ago, back in the early days of the Internet...

John :-#)#

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Reply to
John Robertson

Hi there John,

Actually you are partly to blame for their success! But the "JR" we're referring to was the Editor-In-Chief of EA magazine who looked very puzzled when I told him about the ESR meter idea. I could see him thinking "Why would anyone want to make a meter to measure a capacitor parameter no-one's ever heard of?".

Thanks again for all you've done to keep the meters well known. :)

Bob

Reply to
Bob Parker

** The editor of EA mag back when Bob's ESR & Low ohms Meter meter was published was Jim Rowe.

A number of my designs, mostly for items of test equipment or audio related were also published in EA between 1985 and 1998 - so around the same time.

.... Phil

Reply to
Phil Allison

If you have those articles in PDF perhaps you could add them to your web site, I'd like to see them!

John :-#)#

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Reply to
John Robertson

Time to repair a spectrum analyzer with a flaky YTO PLL using an ESR meter: about 10 minutes, including the time spent digging around in the parts drawer for a replacement cap.

Time to repair the same unit by "scoping the ripple," monkeying around with a sound card, hooking up caps in parallel, using a carburetor synchronizer as a curve tracer, or whatever other wacky suggestions always seem to be posted in threads where the name of the game is to justify not buying a $25 meter: good luck figuring it out before lunchtime.

-- john, KE5FX

Reply to
John Miles, KE5FX

I guess you don't have an oscilloscope.

Did you remove the cap to measure its ESR?

If you suspected the cap, why not just clip-lead another cap in parallel?

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
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Reply to
John Larkin

I can't believe *YOU* of all people thinking this is a viable approach.

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Reply to
Cursitor Doom

What do you find wrong with the concept?

Actually, I would scope around before doing anything else. The ripple waveform of a high-ESR cap will be distinct. Once you have a probe connected to a scope, there are all sorts of other things to look at. You can't just keep pulling parts and testing them.

I don't have an "ESR meter" or a "transistor tester" or any of those kind of things. But then I'm a circuit designer, not a repair tech.

I was just measuring the inductance, saturation behavior, and leakage inductance of a custom toroidal transformer. I did all that with a function generator and a scope. I wouldn't trust any "meter" to do those measurements. Actually, the AADE LC meter came close on leakage inductance, about 100 uH, but was about 4:1 low on winding inductance, which is actually about 2.5 henries.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
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Reply to
John Larkin

The fact that there are at least several dozen axial electrolytics in the instrument in question, few of which are accessible during operation without dragging out the PCB extenders.

If experience tells you that a symptom is >50% likely to be caused by a bad cap -- and it does -- then it's silly not to try the shotgun technique first.

I enjoy doing both on occasion. Opening up a nice old piece of gear from companies like HP or Tek is like entering a temple. Sometimes, though, you don't have time for the whole Indiana Jones tour, and you just want to get your gear up and running and get on with your day. That's when an ESR meter can come in handy.

-- john, KE5FX

Reply to
John Miles, KE5FX

Heh, let's not go there

-- john, KE5FX

Reply to
John Miles, KE5FX

It is. Done it plenty of times. So have armies of repair people.

NT

Reply to
tabbypurr

** This link gives you pdf scans of the relevant issues of EA magazine.

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May 1985: True RMS Adaptor ( for DMMs )

May 1988: Power transistor tester

Feb 1989: Low Distortion Oscillator #1

Mar 1989: Low Distortion oscillator #2

Dec 1996: Miniosc ( pocket audio oscillator )

Jun 1997: RMS Current Monitor ( for mains power )

Aug 1997: Audio Frequency Shifter ( for PA systems )

Feb 1998: FET DI Box ( for musicians)

July 1998: Variable Frequency Drive ( for hi-fi turntables )

The Miniosc was the most popular design, kits were on sale from Altronics for a long time.

.... Phil

Reply to
Phil Allison

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