Author Topic: What about home made (ESR) Meter ?  (Read 69046 times)

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Offline Kiriakos-GRTopic starter

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Re: What about home made (ESR) Meter ?
« Reply #25 on: October 06, 2011, 07:12:06 am »
About the meter for the ESR tester I have run in to problems,  the local stores haves 100uA 150 200 300 but no 50uA in stock,
and it costs 7 Euros.
And one cheap analogue multimeter about 8 Euros. 

From the other hand , the Italian circuitry shows that the connected multimeter is set to 500mA !!
How can this be right ?  when the battery is a single 9V !! 

 

Offline Balaur

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Re: What about home made (ESR) Meter ?
« Reply #26 on: October 06, 2011, 07:38:08 am »
About the meter for the ESR tester I have run in to problems,  the local stores haves 100uA 150 200 300 but no 50uA in stock,
and it costs 7 Euros.
And one cheap analogue multimeter about 8 Euros. 


You can use any reasonably-sized galvanometer that the opamp can safely drive. Obviously, you will need to adjust the pot + resistance in series with the galvanometer in order to adjust the full-range (0 ohms indication).

There are two main things that are useful with the schematic you selected:

- Verify whether the amplitude of the signal on the output of the transformer is low enough.
The original transformer has a 400:20 ratio. That means that a 5V peak-to-peak signal generated by the first opamp will become a 250mV at max applied on the tested capacitor. This low value is required to not polarize any junctions if you test the cap in circuit. If the transformer you use has a different ratio, you will need to adjust the second opamp gain to not saturate the rectified signal for low ESR values (basically, when test leads are shorted, the output of the second opamp should be as high as possible but no saturation)

- Instead of the single adjustment pot, use resistor and a pot. This way, you will have a much better adjustment window.

Cheers,
Dan
 

Offline Balaur

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Re: What about home made (ESR) Meter ?
« Reply #27 on: October 06, 2011, 07:50:41 am »
From the other hand , the Italian circuitry shows that the connected multimeter is set to 500mA !!
How can this be right ?  when the battery is a single 9V !!

Are you looking at the picture of the multimeter?

The original galvanometer is supposed to be 500 microamps. The gentlemen on the indicated link (http://www.qsl.net/iz7ath/web/02_brew/15_lab/06_esr/index.htm says that he used a 1mA galva with a transistor amplifier. Why? You just need to adjust the series resistors.
 

Offline Kiriakos-GRTopic starter

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Re: What about home made (ESR) Meter ?
« Reply #28 on: October 06, 2011, 02:32:36 pm »
You are totally correct Balaur ... 

In this case if I start the Italian idea I will need a 500uA meter, and no extra amplification stage. 

Thanks for the info..  ;)

The good part is that I have not start anything yet,
I would prefer to make a full scale ESR tester, and not to convert a multimeter.
The IC1=TL084 needs more voltage, like steady  9-10V .
And so it can not be powered by batteries if you seek 100% success.
But the first design it can be powered with 9V or less.

Any way, there is still some time for suggestions .   :)

 
 
 
 

Online BravoV

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Re: What about home made (ESR) Meter ?
« Reply #29 on: October 07, 2011, 04:54:20 am »
No Kiriakos, I haven't build it yet, its just your thread here has inspired me to build a non mcu based esr meter, and this Italian design is in my bookmark, thought I'd share it here, also I might join you here building discrete esr meter, its just its not easy to get the enameled copper wires for the inductor here, for the core, we got plenty, for diy winding, I just want a new and fresh copper wire rather than used/ salvaged wire, it might have chipped/scratched enamel.

Already built one using mcu based few years ago and working fine, but it was hijacked and kidnapped by one my good friend here  ???, so I think its time to build another one but non mcu based.

Any way, there is still some time for suggestions .   :)

Another discrete non mcu based variant design as an option -> http://www.siliconchip.com.au/cms/A_103805/article.html

Offline kripton2035

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Re: What about home made (ESR) Meter ?
« Reply #30 on: October 07, 2011, 07:02:40 am »
hello to you all,
to give you some ideas, please consult my esr repository page
you will get lots of schematics, and i hope you will get inspiration for your own esr meter !!!

http://kripton2035.free.fr/esr-repository.html

I'm currently designing a digital esr meter with a minimum component count
(6 including the two protection diodes...) I will post on the site as soon as it works !

regards,
 

Online BravoV

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Re: What about home made (ESR) Meter ?
« Reply #31 on: October 10, 2011, 06:03:11 am »
hello to you all,
to give you some ideas, please consult my esr repository page
you will get lots of schematics, and i hope you will get inspiration for your own esr meter !!!

http://kripton2035.free.fr/esr-repository.html

I'm currently designing a digital esr meter with a minimum component count
(6 including the two protection diodes...) I will post on the site as soon as it works !

regards,

Hey Kripton, its amazing you've collected so many esr measuerement circuits, thanks.

PS : I noticed at one of the German's circuit, you're using google translation, now you can use better one here -> https://www.eevblog.com/forum/index.php?topic=5087.0 and post it at your web site.

Offline amspire

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Re: What about home made (ESR) Meter ?
« Reply #32 on: October 10, 2011, 06:22:25 am »

I'm currently designing a digital esr meter with a minimum component count
(6 including the two protection diodes...) I will post on the site as soon as it works !

regards,

I am looking forward to see this.

I guess it has to have a micro and display, a supply capacitor, the two diodes.

And that leaves one more component - I guess it would have to be a resistor.

I suppose you could get the two diodes in one package and call it one component.

Whatever your plan is, if you can pull it off, it could be very popular.

Richard
 

Offline kripton2035

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Re: What about home made (ESR) Meter ?
« Reply #33 on: October 10, 2011, 09:35:42 am »

Hey Kripton, its amazing you've collected so many esr measuerement circuits, thanks.

PS : I noticed at one of the German's circuit, you're using google translation, now you can use better one here -> https://www.eevblog.com/forum/index.php?topic=5087.0 and post it at your web site.

uh yes Richard's translation is far better than google translate !!!!
I will correct my documents and post them soon. thanks for it !
 

Offline kripton2035

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Re: What about home made (ESR) Meter ?
« Reply #34 on: October 10, 2011, 09:43:02 am »
And that leaves one more component - I guess it would have to be a resistor.
good guess ! ;)

I suppose you could get the two diodes in one package and call it one component.

no I didnt but this is a VERY nice suggestion !
 

Offline saturation

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Re: What about home made (ESR) Meter ?
« Reply #35 on: October 10, 2011, 11:07:46 pm »
FWIW if you have a capacitance meter that show DF , then ESR can be calculated:



DF is really all you need since ESR proportionate to DF.

So ESR = DF x Xc

For more calculations and samples:

http://www.illinoiscapacitor.com/pdf/Papers/impendance_dissipation_factor_ESR.pdf
Best Wishes,

 Saturation
 

Offline amspire

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Re: What about home made (ESR) Meter ?
« Reply #36 on: October 11, 2011, 02:26:57 am »
Capacitance meters are not great at measuring ESR.

Capacitance meters usually want to measure big valued capacitors at low frequencies, because they are concerned at accurately measuring the capacitance.

The ESR reading is usually done at 100KHz and at that frequency, it is just about impossible to measure the capacitance of an big electrolytic, but it is really easy to measure ESR.

Also ESR meters test capacitors in-circuit, whereas capacitance meters need the capacitor removed from the circuit first.

So if you want to measure ESR, nothing beats a good ESR meter.

Richard.
 

Offline Conrad Hoffman

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Re: What about home made (ESR) Meter ?
« Reply #37 on: October 11, 2011, 04:39:42 am »
As owner and collector of many capacitance bridges, I have to agree with Richard. Almost all normal bridges and meters are incapable of measuring big caps at high frequencies. If you want esr, an esr meter is quite handy. I will say however, that I've never seen a bad capacitor that didn't reveal itself, usually in-circuit, with a conventional low frequency dissipation factor measurement. If DF is high and/or Cp is low, it's toast. The only time you can't get good results with an in-circuit measurement is if the cap is already shunted by some low impedance.
 

Offline kripton2035

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Re: What about home made (ESR) Meter ?
« Reply #38 on: October 11, 2011, 06:44:50 am »
hi,
to follow the nice idea from Richard of putting the two diodes in the same package,
does anyone ahave a reference of a double reverse schottky diode in a single package ?
like the bat54s (the s is important must be reverse diodes) but with higher voltage rating like 500v or 1000v ?
thanks.
 

Offline amspire

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Re: What about home made (ESR) Meter ?
« Reply #39 on: October 11, 2011, 07:03:33 am »
hi,
to follow the nice idea from Richard of putting the two diodes in the same package,
does anyone ahave a reference of a double reverse schottky diode in a single package ?
like the bat54s (the s is important must be reverse diodes) but with higher voltage rating like 500v or 1000v ?
thanks.

Schottky diodes cannot be high voltage - the physics doesn't allow it.

But aren't you putting them back to back, so the maximum voltage across the diodes is one diode drop?

Richard
 

Offline kripton2035

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Re: What about home made (ESR) Meter ?
« Reply #40 on: October 11, 2011, 12:02:06 pm »
yes I put them back to back like in the bat54S (and not bat54a or c they are the same direction)
ok for "normal" diode. I only found same direction diodes in a single package ...
« Last Edit: October 11, 2011, 12:04:37 pm by kripton2035 »
 

Offline amspire

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Re: What about home made (ESR) Meter ?
« Reply #41 on: October 11, 2011, 12:20:52 pm »
So you don't need a high voltage rating. The diodes never have more then one forward diode drop voltage across them, so you can use any Schottky you can find.

Richard
 

Offline amspire

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Re: What about home made (ESR) Meter ?
« Reply #42 on: October 11, 2011, 12:54:21 pm »
I am assuming you are testing below the Schottky forward voltage.

Here is my suggestion from Digikey:

http://search.digikey.com/us/en/products/CDBHD240-G/641-1213-1-ND/1678631?vendor=641

The diodes are 2A each, and the bridge has 4 diodes so that will make 4A current capacity in each direction. The 8.3 mSec surge current is 100A for each pair.

The forward voltage of these will be under 200mV, but if you need more voltage, the CDBHD260-G has double the forward voltage of the 240.
« Last Edit: October 11, 2011, 01:01:07 pm by amspire »
 

Offline amspire

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Re: What about home made (ESR) Meter ?
« Reply #43 on: October 11, 2011, 11:47:12 pm »
I hadn't thought of that. Nice!

For the ESR meter, you need to measure sub ohm resistances, and it looks like the circuit in the app note has way too much series resistance. If the series resistance is reduced to 1 ohm, then it will limit the current at 1A. A bit much.

But I will definitely keep it in mind for protecting high impedance inputs.  It has to compete of course with the PTC now in every multimeter.

Richard
 

Offline amspire

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Re: What about home made (ESR) Meter ?
« Reply #44 on: October 12, 2011, 05:06:38 am »
The force and the sense connections can be seperate but the biggest problem here is how to add some sort of protection without going above 6   5 components for the total design.

That seems to be the design mission.  ;D

Richard.
« Last Edit: October 12, 2011, 05:09:53 am by amspire »
 

Offline kripton2035

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Re: What about home made (ESR) Meter ?
« Reply #45 on: October 12, 2011, 09:57:46 am »
AcHmed99,
yes it is to protect the input of the esr meter
but as richard already said, it is for measuring around the ohm value
so it's not a good thing to insert a 1kohm resistor in the measure ...
anyway thanks for the trick.

I'm looking for a two diodes in one package component
but all I see are for rectifiers of smps, so they have the cathode of the diode connected together
I want the two diodes reversed.
richard say it doesnt exist in schottky, so does it exist in normal diode with voltage like 500V ?
I repeat this is to protect the measuring circuit from charged capacitors of smps ...
thanks
 

Offline amspire

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Re: What about home made (ESR) Meter ?
« Reply #46 on: October 12, 2011, 10:16:18 am »
I have no idea how you are going to protect the meter with two reversed diodes.

You have got me stumped there.

They cant be in series with the test capacitor, and if they are in parallel with the capacitor, they will do nothing as no electro will ever have more then 450VDC.

What is left?

Richard
 

Offline kripton2035

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Re: What about home made (ESR) Meter ?
« Reply #47 on: October 12, 2011, 11:15:13 am »
some protection like this one :
 

Offline amspire

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Re: What about home made (ESR) Meter ?
« Reply #48 on: October 12, 2011, 11:28:22 am »
The maximum forward drop possible across the diodes in that circuit is one diode drop, so any diode rated at more the  1V will be fine.

One diode is always forward biased, and the trick is to keep the measurement voltage below the turn-on voltages of the diodes.

The only reason someone used the 700V 1N4007 diodes was because it is a very common, very cheap part.

So you can use your BAT54S diodes or for more rugged diodes, you could use my bridge rectifier package.

Richard.
 

Offline kripton2035

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Re: What about home made (ESR) Meter ?
« Reply #49 on: October 12, 2011, 01:01:38 pm »
I also have an UC3611 bridge that is rated 3A
will certainly do with it...
regards,
 


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