Elektor Electronics

Anyone get Elektor Electronics magazine http://213.222.12.205/Default.aspx?tabid=27&year=2005&month=9&art=52895&PN=O n

Hopeless NZ bookshops have not put it on the shelf yet,

Does anyone know what capacitors range the ESR meter does?

Reply to
Eric
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"Eric the Kiwi"

** A waste of perfectly good trees.

** Trees 1, Elektor 0.
** Who bloody cares ??

Every second DMM on sale measures capacitance well enough.

For PSU electros an ESR meter is all you need and Bob Parker's one is a winner.

If an electro passes the ESR test - then it has its original (marked) capacitance value.

If an electro fails the ESR test - then it goes straight in the bin.

Capice ?

......... Phil

Reply to
Phil Allison

Why is that Phil? Is it because the dont publish designs based on pre-historic components?

Perhaps the ex roadies dont like mags that publish mostly digital designs

Reply to
The Real Andy

Because you can get same thing in a pdf

Reply to
Tom

Now why did I think as I wrote the question, "I would most unlikely get a answer, just pathic replys from children that have nothing better to do"

Reply to
Eric

On Sun, 11 Sep 2005 08:42:14 +1200, "Eric" put finger to keyboard and composed:

With respect, I can't see that this question makes any sense. An ESR meter measures ESR, not capacitance. Ideally the capacitor's C should not affect the result because it should look like a S/C to the test signal.

I don't know anything about the Elektor meter, but Bob Parker's meter applies charging pulses of three different amplitudes to the capacitor under test, and then compares the voltage to an internal reference capacitor. The assumption is that the pulse is of sufficently short duration so as not to appreciably charge the test capacitor. AFAICS, the larger the cap, the more accurate the measurement. As for very small caps, I would think that the meter's internal time constants would be selected so as to accommodate the smallest expected values of capacitance. At the very worst, the meter would overestimate the ESR. In this case the user could check the reading against a known good cap of the same value.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

Reply to
Franc Zabkar

This is aus.e;ectronics, and it does reflect the nature of the industry in australia :)

I used to be an elektor subscriber and they continue to send me mags. If this one turns up in the post I will email you.

Reply to
The Real Andy

Looking at a review of ESR meters I note that they do vary in respect of the range of caps they can accurately check for ESR - especially at the lower end of the range I gather

David

Franc Zabkar wrote:

Reply to
quietguy

On Wed, 14 Sep 2005 23:57:28 GMT, quietguy put finger to keyboard and composed:

Well, that's what I expected in the worst case.

Anyway, I notice that the ESR table on Bob Parker's Mark 1 meter goes down to 1uF, so I tried the following test using five Hitano EXR series 105 degC 1uF 100V low ESR electrolytics (WES code 1EXR100).

individual ESR measurements (1uF): 3.1, 3.3, 3.6, 3.8, 3.8 ohms all five in series (0.2uF): 18 ohms all five in parallel (5uF): 0.67 ohms

The results suggest that the meter is reasonably linear in the range

0.2uF - 5uF.

The next readings are for used, 250V, film, mains rated X2 caps:

C (uF) ESR (ohms)

----------------------- 1.0 1.4 1.4 0.82 1.5 1.5 0.47 3.3 2.9 3.5 0.22 7.7 0.10 19 19

I would have thought that the ESR for this type of cap was negligible (< 0.5 ohm ???). If so, then the readings must reflect the capacitance's contribution to the measurement process. If I understand Bob's design correctly, the capacitance should contribute a "resistance" value of dt/C (= dV/Ipulse), where dt is the duration of the charging pulse. For example, a 1us pulse into an ideal 1uF cap should make it test like a 1 ohm resistance, whereas an 0.1uF cap would measure 10 ohms.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

Reply to
Franc Zabkar

"Franc Zabkar" quietguy

** Bob's brilliant ESR meter is very clearly intended to test ** ELECTROS ** - while in circuit, in faulty gear !!

The whole reason for testing the electros is because at the end of their useful life, the " juice " inside dries out sending the ESR value high.

The principle of operation relies on the fact that at a frequency of about

100kHz, an electro's impedance it at its minimum value - so nearly equal to the intrinsic internal resistance or ESR !!

Very low value electros, like 1 uF, need a slightly higher test frequency for best accuracy.

However, plastic film capacitors need to be tested from 1 to 10 MHz to find their true ESR values - only a variable frequency ESR meter could do that as you need to find the series resonance .

Film caps do not vary in ESR throughout their life - so no need for such testing exists.

......... Phil

Reply to
Phil Allison

Ive tested faulty electro caps which still give a 'pass' according to the table. Ive also got some caps quite visibly leaking & buldging that test 'ok 'with my ESR & a CAP meter. Just something to bear in mind for amatures (like me).

Reply to
S Roby

The tech at work pulled them out(replaced them) to fix power supplies.

Reply to
S Roby

"S Roby"

** What make you sure they were faulty then ??

** So they were electrically OK - but visual reasons existed to replace them .

............. Phil

Reply to
Phil Allison

"S Roby" "Phil Allison"

** I repeat:

What make you sure they were faulty then ??

The tech may have replaced them as a precaution or because they were of a certain age etc.

........... Phil

Reply to
Phil Allison

ESR meters aren't some kind of mystical box which magically tell you with 100% accuracy which capacitors are defective. They're just one more test instrument which tells an experienced user with a good knowledge of electronics about another characteristic of capacitors which is very relevant to how well they're doing their job. ESR meter readings have to be intelligently combined with other factors including the physical state of the capacitor being tested. I never cease to be amazed by how little electrical knowledge many ESR meter users have. The DSE meter was designed specifically for service technicians, but many of them have been bought by hobbisyts and "amatures", a lot of whom still seem to think that ESR equates to leakage and/or that the higher the ESR the better. I agree with Phil's comments... he understands and appreciates where ESR meters fit into the overall scheme of things. :) That's my 2c worth.

Cheers Bob

On Fri, 16 Sep 2005 17:43:49 +1000, "Phil Allison" wrote:

Reply to
Bob Parker

On Thu, 15 Sep 2005 18:41:49 +1000, "Phil Allison" put finger to keyboard and composed:

The test signal is not sinusoidal. While the Xc of a 1uF cap at 100kHz is a negligible 1.6 ohms, that is not what the meter sees. The test signal, at least for the Mark 2 version, is an 8us current pulse with a frequency of 2kHz. The voltage seen at the meter's terminals would be given by ...

V = (I * R) + (I * dt/C)

The meter assumes it is seeing a pure resistance (R'), so it applies Ohm's Law and comes up with ...

R' = V/I = R + dt/C

This reduces to R' = R + 8 in the above case.

So if one were to apply the design principle described by Bob in his SC article, one would expect the meter to read 8 ohms for a perfect

1uF capacitance. This is not what I observe in practice, but it may at least partly explain the higher than expected readings for the film caps.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

Reply to
Franc Zabkar

On Thu, 15 Sep 2005 18:41:49 +1000, "Phil Allison" put finger to keyboard and composed:

I did not suggest that such testing was required. I merely wanted to see how the meter would evaluate "perfect" caps. To paraphrase Dirty Harry, a man's gotta know his test equipment's limitations.

Regardless, manufacturers quote a loss tangent figure for these types of caps.

See this datasheet:

formatting link

Tangent of loss angle at 1 kHz 10 kHz 100 kHz

---------------------------------------------------- C

Reply to
Franc Zabkar

I repeat The tech at work pulled them out(replaced them) to fix power supplies.

The power supplies had spikes on the output (clearly seen on the scope) , fixed by replacing caps.

Reply to
S Roby

"Franc Zabkar" "Phil Allison"

** No need to be, since the impedance minimum of an electro has a very broad range.
** 1.6 ohms is very far from negligible for a film cap.

It is, however, what the ESR meter reads with a 1uF film cap.

** It is an coupled AC signal, remember.

............. Phil

Reply to
Phil Allison

"Franc Zabkar" "Phil Allison"

** That is a tedious irrelevance.

The fact explains why Bob's ERS meter is set up to test electros ONLY.

It is NOT, repeat NOT , a precision ESR tester.

-------------------------------------------------------------

** Another tedious irrelevance.

Bob's ESR meter is clearly stated to be ONLY for electros.

Its only job is to pick out the ones that have gone bad in service.

-------------------------------------------------------------

** More tedious bloody irrelevances.

BTW The result figures are jumbled.

What a colossal , pedantic PITA you are Zabkar.

....... Phil

Reply to
Phil Allison

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