esr or cap tester

[RusMike]

Re: esr or cap tester

Could you send me a PM

has done

[brethin]

Re: esr or cap tester

yes we have both version (3.1 and 4.0S) in stock now.
The only difference for 4.0S is another LCD we used (segments vs graphic in 4.0)
But power consumption became less.

Could you PM me as well. I am intrested in being a USA reseller/distributor.

[lucidbarrier]

Re: esr or cap tester

has done

Thank you, payment sent!

[twixt]

Re: esr or cap tester

Twixt, are you professional writer?

Hi, Mike. No, I'm not a writer by profession. However, technical writing is frequently a part of my work.

A big part of my job is making sure users can actually comprehend both the software and hardware they are using.

In many cases, I find the difference between success and failure in a computer project hinges on having users understand how to use the system competently and effectively. Users can't do that if they don't understand their part in the total scheme of things - as well as what to do when things go wrong, go wrong, go wrong....


As a result, I consider a good command of the english language to be a requirement for success in my field.

However, if I can have some fun along the way - well why not?


twixt

[scokljat]

Re: esr or cap tester

I finally got my ESR 4.0s

But, it always shows much hihger capacitance than expected and specified on the cap itself. Brand new 47uF cap is displayed 66uF, 1000uF is displayed 1140uF, 470uF is displayed 531uF, 22uF is displayed 30.6uF, 10uF is displayed 12.6, etc....

Same caps measured with fluke 175 show much different values, usually little less than specified on the cap itself, but never as much as ESR4.0s displays. Sometimes it drifts more than 50%.

I can't be sure if it shows correct ESR as I don't have other ESR meter for reference.

I was very happy because ESR4 measure capacitance, but I'm affraid it's unusable in that matter :-(

Is it normal for all ESR4's or just my ESR4 has some problem with capacitance or some misadjustment?


Cheers!

Suad

[twixt]

Re: esr or cap tester

I finally got my ESR 4.0s

But, it always shows much hihger capacitance than expected and specified on the cap itself. Brand new 47uF cap is displayed 66uF, 1000uF is displayed 1140uF, 470uF is displayed 531uF, 22uF is displayed 30.6uF, 10uF is displayed 12.6, etc....

Same caps measured with fluke 175 show much different values, usually little less than specified on the cap itself, but never as much as ESR4.0s displays. Sometimes it drifts more than 50%.

I can't be sure if it shows correct ESR as I don't have other ESR meter for reference.

I was very happy because ESR4 measure capacitance, but I'm affraid it's unusable in that matter :-(

Is it normal for all ESR4's or just my ESR4 has some problem with capacitance or some misadjustment?


Cheers!

Suad

Hu, Suad. Some things to know about electrolytic capacitors:

1. It is common for electrolytic capacitors to have asymmetrical tolerance. A typical value is -20%/+80%.

2. The reason for the above is due to dielectric resorption during capacitor storage. Go to the following page for information on how electrolytic capacitors are made:

http://www.chemi-con.com/index.php?o...id=2&Itemid=16

3. It is important to understand that the capacitance of an electrolytic is inversely proportional to the thickness of the aluminum oxide layer (dielectric) on the surface of the anode foil. See the following Wikipedia article for more information on electrolytic capacitors:

http://en.wikipedia.org/wiki/Electrolytic_capacitor

4. Thus, the rated capacitance of a capacitor is a function of the "forming voltage" - which induces the formation of the oxide layer on the anode foil in the first place - as well as the "aging" voltage which reforms the oxide layer after the capacitor is manufactured and installed in its "can". The "aging" voltage is specifically applied in order to accomodate any oxide-layer damage which occurs during the various steps in the manufacturing process.

5. A characteristic of the electrolyte used in electrolytic capacitors is it attacks the oxide layer on the anode foil and gradually reduces the thickness of the dielectric layer if the capacitor is left uncharged. Thus, all capacitors will increase in value as they are stored - but their ability to withstand voltage will decrease as the dielectric layer gets thinner.

6. When you first hook up a capacitor which has been stored for a while, the dielectric layer is "reformed". The layer builds up to an equilibrium value which is a function of the "ongoing forming voltage" - which is the voltage differential actually applied to the capacitor while in-circuit - not the original forming voltage used to generate the oxide layer in the first place.

7. From the above, it can be seen that running an electrolytic under its "rated" voltage will automatically allow the electrolyte to gradually resorb the oxide layer until such time as the thickness of the oxide layer and the "ongoing forming voltage" come into equilibrium. As an example, installing a capacitor rated at 2000uf/35V into a circuit running at 25V will cause the capacitor to gradually increase its "real world" value over the capacitor's lifetime - as the dielectric thins to come into equilibrium with the "real world forming voltage" of the circuit in which that capacitor is actually running.

8. Thus, there is no such thing as a "typical" value for an Electrolytic Capacitor's "actual" capacitance - it varies depending upon how long the capacitor has sat in storage, what forming/aging voltage was used at the factory, and what voltage the capacitor is actually being used at in-circuit.

9. Because capacitance always increases when the capacitor is stored unused, the tolerance for an Electrolytic is much higher in the positive direction simply as a result of the physics of how the oxide layer(dielectric) of the electrolytic is created in the first place - and then how the oxide layer is maintained by the "operating forming voltage" when the capacitor is active and in-circuit.


With the above background information/understanding in place, we come to your question about the actual measured capacitance in-the-real-world:

1. How long have those capacitors remained in storage?

2. What temperature were they stored at?

Note: Both the above questions have to do with the process of dielectric resorption. High storage temperatures accelerate the rate of resorption.

This also explains why forming is done at higher-than-rated voltage. This allows the capacitor to be stored for several years and then "reformed" successfully when put in-circuit at the rated voltage.

It also explains why capacitors that have been in storage for a loooooong time can spontaneously short-out and/or vent when put in-circuit without going through a dedicated process to "reform" the oxide layer (dielectric) in a safe manner.

3. Because Mike's meter uses such small testing voltages (which is the reason it can be used in-circuit since the voltage is too low to cause diode or transistor conduction) the dielectric can get very thin indeed (from resorption) without the capacitor failing when tested. However, the actual capacitance value may therefore be higher than the rated value because of that resorption.


And finally, the variation in reported capacitance values between the Fluke and the ESR4.0s:

1. Because your ESR4.0s is consistently high, I suspect it may not have been properly calibrated after manufacture. Check with Mike to see what he thinks about the difference between the sets of readings on the Fluke and the sets of readings on the ESR4.0s.

2. I do know that Mike changed the testing methodology for the capacitance measurement in order to increase resolution for small capacitance values. Again, check with Mike to see if this may be a cause of the difference between the Fluke readings and the ESR4.0s readings.

3. Do you have acess to a third meter (eg: from someone else you know) who can measure that same set of capacitors and give you their readings? This would provide further clues.


Hope this helps.

[budm]

Re: esr or cap tester

How is the meter calibrated? Using reference capacitor with know value (its value has been verify with calibrated cap meter) for calibration. The meter will be as useful as how well it is calibrated.

[mariushm]

Re: esr or cap tester

The capacitors can also measure different capacity depending on the frequency used to measure the ESR an capacity.

I've posted yesterday a link to another forum thread where a guy was doing a sweep from 1 kHz to a few Mhz and you can see both the ESR and the capacity changes.

Here's the thread : http://www.eevblog.com/forum/product...the-moment/30/

Read "The Electrician"'s posts.

The Fluke may be measuring at a certain voltage threshold and through some tehnique while the esr meter uses a higher frequency..

On the next page he shows a 50uF capacitor, which is around 50uF at 60-120Hz but at 1kHz it's already 66.8uF and gets close to 100uF at 100 kHz:



Other capacitors behave the other way around - here's an electrolytic 47uF / 16v he posted:



You can see the cap already measures 40uF at 1kHz and goes down to 4.6 uF at 100 kHz - it's probably a general purpose capacitor, not meant for high frequency circuits.

So I don't know, I guess the real value depends on the frequency and what KIND of capacitors were used to calibrate (maybe there's a series of adjusting values stored inside the processor code or eeprom).

Anyway, the ESR meter does a good approximation of the ESR (it's not the actual ESR of a capacitor in the real sense of the term) and as a plus it gives a good approximation of the capacitance.

Most capacitors have a +/-20% tolerance, so it's not a problem if the meter shows a capacity a bit higher than others, it doesn't mean necessarily that it's uncalibrated.

[scokljat]

Re: esr or cap tester

1. How long have those capacitors remained in storage?

2. What temperature were they stored at?

Note: Both the above questions have to do with the process of dielectric resorption. High storage temperatures accelerate the rate of resorption.

First, thank you very much for highly elaborate answer

I don't know how long have those capacitors remained in storage. They are bought brand new and I have them "on stock" for my hobby projects and repairs. They are held in my apartment at +25C no more than one year. I don't know how long they remained in storage in the shop before I bought them. I also measured some used caps, pulled from working devices. Also displayed high on ESR4's.

And finally, the variation in reported capacitance values between the Fluke and the ESR4.0s:

1. Because your ESR4.0s is consistently high, I suspect it may not have been properly calibrated after manufacture. Check with Mike to see what he thinks about the difference between the sets of readings on the Fluke and the sets of readings on the ESR4.0s.

2. I do know that Mike changed the testing methodology for the capacitance measurement in order to increase resolution for small capacitance values. Again, check with Mike to see if this may be a cause of the difference between the Fluke readings and the ESR4.0s readings.

3. Do you have acess to a third meter (eg: from someone else you know) who can measure that same set of capacitors and give you their readings? This would provide further clues.

I have a cheap multimeter capable of measuring capacitance up to 20uF. It tends to measure and show even lower results than fluke! E.g. a 10uF/350V cap from my old plasma which I suspected was bad measured with my YFE multimeter shows 7.7uF, on Fluke175 it shows 8.5uF (as I remember), and 10.4uF on ESR 4's with ESR of 8.4ohm. Other 10uF/350V cap removed from the same YSUS board shows 8.6uF on YFE and 11.8uF with ESR 2.99ohm on ESR4's. Other 10uF/350V caps from same board have 5.0ohm, 7.0ohm, 3.0ohm and 2.0ohm ESR. So, the first one is definitely bad, and other are not as new so I replaced them all with Panasonic EE 10uf/450V. Fluke meter was borrowed from my friend and I have to return it back...

I have send an email to Mike, I'm sure he will explain it all and help me to calibrate my ESR4 if needed.

Cheers!

Suad

[scokljat]

Re: esr or cap tester

Just got reply from radiodevices.

They say:

"sure you can adjust precision with pots R9 and R15
just connect cap (about 1000...2200 uF) into socket and tune R9 to get readings the same as say your FLUKE

after that insert resistor 10 ohms into socket and tune R15 to get 10.0 on LCD then do calibration and check for low-ohms resistors (0.1.... 1 ohms)"

Well OK, I'll borrow Fluke again and do some testing and adjustment. For R15 adjustment I suppose it's good idea to use 1% resistor.

I'm still trying to justify high capacitance reading of ESR4.0s. I'll test some new caps as well as some good used caps and if all show high I'll readjust it.

Cheers!

Suad

[budm]

Re: esr or cap tester

Cap reading

[RusMike]

Re: esr or cap tester

Yes as it was written above real capacitance value may vary within +/-20% more, so that's why i think not very important to know EXACT value, and it can depend on measuring method you use. Sure everyone can tune his device with pot R9 (capacitance) and R15 (R-ESR), just pay attention for that you must calibrate it after EVERY R15 tuning and AFTER THAT need to check for low-ohms resistors to provide maximal exact readings within band 0....1ohm (use resistors 0.1, 0.33ohms or so...)

[RusMike]

Re: esr or cap tester

How is the meter calibrated? Using reference capacitor with know value (its value has been verify with calibrated cap meter) for calibration. The meter will be as useful as how well it is calibrated.

Absolutely. we use low-ESR caps which were measured with ATLAS ESR60

[RusMike]

Re: esr or cap tester

mariushm, twixt THANKS for usefull information!

[RusMike]

Re: esr or cap tester

Could you PM me as well.

has done

[emardee]

Re: esr or cap tester

Hi,

Has anyone got any experience of a device like this one?
http://r.ebay.com/IN5GZx
(UNI-T T612 listed on ebay)

It supposedly tests a whole load of stuff (says it does: L/C/R/DCR/Q/D/θ/ESR), not just ESR, but not sure if it is worthwhile or not. Does it work well? Is it good value for money compared to separate devices?

Thanks

Mike

[budm]

Re: esr or cap tester

Not experience with this brand, but if it does all those functions, then it is a good value for the money.

[mariushm]

Re: esr or cap tester

I have the Unitrend UT61E multimeter ... it's excellent meter for the money.

Seen lots of reviews for various multimeters of theirs, some are just like this 61E excellent value for money, but others, even some versions from the same series for example UT61C are of relatively average quality or have some minor flaws (like using glass fuses instead of better but slightly more expensive ones).

So it's as if they have several teams doing designs or something like that, you can't be sure of how one of their products is until after you see it reviewed.

Overall, if I needed one lcd meter, I would buy it, it can't be worse than other no-name or various OEM clones. Price seems good.

Tip: It's also available on Dealextreme, with free shipping: http://dx.com/p/uni-t-ut612-2-8-lcd-...-1-x-9v-132226

It would be more reliable than a random eBay seller, and might be cheaper than eBay.
But some people here dislike Dealextreme for selling fake capacitors. I bought from them in the past stuff (not capacitors) and on these more expensive things it's safe to buy, they're not fake.

[emardee]

Re: esr or cap tester

Thanks.

I haven't been able to find any review of this unit. I'm guessing the unit is too new to have been reviewed yet. It looks like it has a data logging feature over USB to a computer, but it is all a bit vague.

My immediately need is to be able to get a way to test ESR, hence reading the whole of this thread, and posting here.

I already have a reasonable DMM (with Analogue needle too!), which has Capacitor test, frequency test, resistance, voltage etc. So some of these features will be duplicated for me, but then it still looks to be good value overall (if it works well!). Equally, ESR is the main thing I need right now, and being able to test inductors in a SMPS would be handy too.

I guess I should post a picture of my current DMM (when I get home from work), as someone will be able to confirm how much extra the UNI-T can do compared to my current DMM.

Ebay looks to be a bit cheaper for me in NZ than DealExtreme, but not a lot in it.

Thanks again for your help

Mike

[caledor]

Re: esr or cap tester

For RusMike

Mike, could you send me a PM or email and give me details on how to order a V4.0S to Spain?

Thanks