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Real simplest and most practical ESR meter circuit

abdulbadii

New Member
Any experienced expert in creating some testing instrument here ?

What'd the simplest, cheapest and most practical ESR meter circuit be, requiring only 6 V PS (not 9 as usually) while it's reliable enough to perform a test with ~ 2% (or even just 2.5%) tolerance
 
Last edited:

whit3rd

New Member
The answer depends on your ESR resistance range; a CMOS '555 can do a few milliamps of square wave,
and an oscilloscope readout will show resistance at the 0.1 ohm level, but some
low-ESR capacitors are spec'ed for 0.01 ohms (ten milliohms), so a 2%
tolerance means detecting a (0.02 * 0.010amp *0.010 ohms = 2 microvolts)
very tiny step voltage. It would be best to use a four-wire probe for such a measurement.

Large-ish electrolytic capacitors (330 uF) and up that fail due to high ESR are usually
in the 1.0 ohm ++ range, and you don't need accuracy to know that they're bad.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
The answer depends on your ESR resistance range; a CMOS '555 can do a few milliamps of square wave,
and an oscilloscope readout will show resistance at the 0.1 ohm level, but some
low-ESR capacitors are spec'ed for 0.01 ohms (ten milliohms), so a 2%
tolerance means detecting a (0.02 * 0.010amp *0.010 ohms = 2 microvolts)
very tiny step voltage. It would be best to use a four-wire probe for such a measurement.

Large-ish electrolytic capacitors (330 uF) and up that fail due to high ESR are usually
in the 1.0 ohm ++ range, and you don't need accuracy to know that they're bad.
Exactly, for service purposes you don't need any sort of accuracy - and duff caps are mostly MUCH higher than the 1 ohm whit3rd suggested.

I've tested, and replaced, thousands of electrolytics - and almost always you go 'wow' when you find a faulty one, and just can't believe it still worked to any degree. Generally you don't even pay attention to the numbers - you just run along the capacitors until one jumps out and grabs you :D

A 330uF at 1 ohm should certainly be changed, but doing so would be unlikely to cure the fault - it's more for future prevention.

A lot depends, as usual, on exactly what the OP is trying to do - if it's simply testing capacitors out of circuit, then the cheap Chinese component tester kits would be fine, as most now do ESR (but not very well in-circuit).

I used a home made (out of TV Magazine) analogue one for a number of years, then bought a Peak Electric one, which I can highly recommend (and they are made not too far from me).

 

Musicmanager

Active Member
I used a home made (out of TV Magazine) analogue one for a number of years,

I made and still use that same TV Magazine Meter .. .. . works for me ..

ESR Meter.jpg


MM
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I made and still use that same TV Magazine Meter .. .. . works for me ..

View attachment 133812

MM

I made two, one for work and one for home, I gave them both away long ago.

Nice job on the scale - presumably the one printed in the magazine?.

I did scan the entire article, but I can't find it any more?.

Edit: If you type in 'esrmeter' in the search box on Windows it finds it for you! :banghead:

This is scanned, OCR'd, and edited from the original articles.
 

Attachments

  • esrmeter.pdf
    119.1 KB · Views: 7
Last edited:

Musicmanager

Active Member
:) I was just going to send to my PDF of the article that you sent me in 2015 !

The scale is the one in the article but I edited it with a bit of software called ' Meter Basic ', quite good.

MM
 

Nigel Goodwin

Super Moderator
Most Helpful Member
:) I was just going to send to my PDF of the article that you sent me in 2015 !

I just couldn't see it - and it was even where I looked :D

Did you build it from that PDF?.

The scale is the one in the article but I edited it with a bit of software called ' Meter Basic ', quite good.

MM
Nice!.
 

dougy83

Well-Known Member
I'm, not sure I remember, but it's unlikely I built it from anything else.
...
Look Familiar ?

MM
That's a different circuit. Yours is using a 74HCT14 (presumably a squarewave oscillator, with LPF); Nigel's is using a bunch of opamps (presumably a "sine"wave oscillator).

Is this yours, MM?
iu
 

Musicmanager

Active Member
Yep .. you're quite right !
My memory isn't what it used to be .. .. .. .. .

Mine is based on the attached article .. .. .

MM
 

Attachments

  • Yorkie's ESR Meter.pdf
    1.3 MB · Views: 2

dougy83

Well-Known Member
Yep, that's the same circuit I posted. I wonder what accuracy you can expect from it. Obviously it works well enough to detect bad caps.
 

Musicmanager

Active Member
Well, I'm only slightly less of a novice now than I was when I built it so the accuracy wouldn't mean a lot to me either way.

It seems to detect a cap with an ESR problem well enough, I successfully used it a number of times; most recently an Instek Bench Power Supply that was explosive - a pair of MOV's burnt to a crisp, a large FET with the front blown off .. .. .. .. .. .etc .. .. .. .. MOV's, Bridge, FET's and most of the caps replaced .. .. now working nicely.

In the article the author actually states that accuracy is not very important so that maybe answers your question.

MM
 

dougy83

Well-Known Member
That's cool that it was handy for fixing the PSU.
Even if it doesn't meet the 2% requirement of the OP, it's so simple that I think I'll have to build one, but will swap out the 74HC14 for a LM555C.

Cheers.
 

Musicmanager

Active Member
You're very welcome .. .. ..

Nothing more than curiosity .. I'd be interested to see the LM555C circuit when you've done ?

MM
 

Nigel Goodwin

Super Moderator
Most Helpful Member
That's a different circuit. Yours is using a 74HCT14 (presumably a squarewave oscillator, with LPF); Nigel's is using a bunch of opamps (presumably a "sine"wave oscillator).

Is this yours, MM?
iu
The article from TV Magazine suggests that using a sinewave is advantageous, I've no idea what difference it makes in practice. I'm presuming the multiple 680 ohms (to increase drive power) and 47nF above are to 'round off' the squarewave to approximate a sine?.
 

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