DIY ESR Meter advice (What one to build?!?!)

[peps1]

Hey guys,

Could really do with a ESR meter to stop me from alway having to desolder a cap leg, so thought I would build one myself!

The trouble is, there are just so many out there its a little daunting, and I'm not sure picking one based purely on what parts i've got in the scrap bin is the best approach. 

So, Im sure a lot of you have made your own and I would really like some recommendations.

p.s

Analog and minimal parts me me happy! 

[Jay_Diddy_B]

Check this thread

https://www.eevblog.com/forum/projects/5-transistor-esr-meter-design/msg171364/#msg171364

Jay_Diddy_B

[Shock]

I'll put it out there, only because I was originally going down the same path as you before I changed my mind.

You might not be aware of the project but there's a $20 (inc shipping) LCR ESR Transitor tester that works very well and can be purchased preassembled on ebay sometimes for as little as $10. The design is of german origin and is documented here http://www.mikrocontroller.net/articles/AVR_Transistortester

It's not analog as they use ATmega microcontrollers and have LCD displays, but if you not sold on the idea of making one yourself it's undoubtedly the cheapest and most feature rich way to go, shy of spending approx $80-$100 for a DER EE DE-5000 handheld ESR meter which is the most bang for buck in commercially made ESR equipment.

If you want to make it yourself, all the code and schematics are there and despite it's complexity it uses very few components and could be made for around $20-$30 if you pickup a display (which are the most complex part) on ebay for a few dollars.
You don't have to make it out of SMD components and it will be quite happy running on a breadboard.

The advantage this has over purely analog meters is it measures other components and when measuring ESR displays the capacitance and ESR simultaneously on screen and is very easy to read and fast to operate.

The $20 ESR can be found discussed in these 2 threads.
https://www.eevblog.com/forum/testgear/$20-esr-lcr-transistor-npn-pnp-mosfet-meter
https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project

[Shock]

Now to complicate matters, you have indicated that you dislike lifting the leg of a component.

If this is very important, you will need to look for a design that supports in circuit testing.  They will have a low test voltage as not to turn on other components in the circuit.  As ESR reads differently at different test frequencies it may be handy to also have a tester that measures at a specific frequency to match data sheets such as 100 KHz.

Despite getting a suitable in circuit ESR meter you are never be 100% sure of the reading, as parallel resistances present in circuit will throw your measurement out, testing the cap out of circuit generally accepted as more conclusive.

Another thing that may sway your decision is if the design can handle charged capacitors.  Otherwise you will need to ensure all caps are drained before testing especially in circuit or risk blowing your meter.

So what I ended up doing was buying a proper desktop LCR/ESR meter for kelvin testing and some frequency support.  A couple of $20 ESR for comparison units to mod or redesign.  I'll also pick up a DER EE DE-5000 at some stage for portable kelvin testing and freuquncy support.  None of these however were really designed to support full in circuit testing

[peps1]

Check this thread

https://www.eevblog.com/forum/projects/5-transistor-esr-meter-design/msg171364/#msg171364

Jay_Diddy_B

Thanks Jay, that look just like the kind of thing Im after, just have a little trouble seeing how to hook up the pot as it seems to be missing in the schematic and unattached to anything in the photos?

Now to complicate matters, you have indicated that you dislike lifting the leg of a component.

If this is very important, you will need to look for a design that supports in circuit testing.

Yes, the inline functionality is very important to me, but iv seen a few of those AVR testers with a zero button im assuming is for adding leads for inline testing......but they are twice the price.

[Jay_Diddy_B]

Hi Peps1 and the group,

Thanks Jay, that look just like the kind of thing Im after, just have a little trouble seeing how to hook up the pot as it seems to be missing in the schematic and unattached to anything in the photos?

The wiring for the meter is like this:

      TP4 to the Meter + terminal

      Meter - terminal goes to the wiper of the pot

      One end of the pot goes to TP3 on the board

As you turn the pot clockwise the resistance should decrease.

The only critical parts on the schematic are the diodes D3 & D4 they are small signal Schottky diodes 1N5711. You could also use something like Germanium diodes like OA91 or 1N34.

For the transistors they are not critical, you can use BC548 for the npn and BC558 for the pnp

Let me know if you have any other questions.

Jay_Diddy_B

[Shock]

The DER EE DE-5000 is about the cheapest I've seen with 4 wire kelvin testing (leads become less an issue). A zero button would be to short the leads for quick calibration, so would probably be roughed in even if you had longer leads. 
I've seen several dozen designs and models. If the design does not specifically mention overload protection, discharge or in circuit testing it won't have it. There is only a handful that do.  Most notably on the cheap end of the scale.

The Blue ESR meter (pre built or kit) can be used in circuit which applies 100mV across the cap.
The EVB ESR meter (pre built or kit) can do in circuit and has overload protection but not sure about the discharge.
(both are based on Bob Parker designed DSE K-7214 kit)
The Peak Atlas ESR Plus (commercially made ~$160) supports in circuit testing (have no spec for this), 100kHz frequency, discharge and also has an audio alert. They say it's accurate enough to be used for trace testing as well.  You might want to check that requires no button pushing prior to each test in circuit.

But you still have to pull some caps out to test them properly.

[PaulAm]

Here's a link to all kinds of ESR meters you can build or buy:
http://kripton2035.free.fr/esr-repository.html

They link to the Eevblog 5 transistor circuit as well.

I built this one:

http://members.shaw.ca/swstuff/esrmeter.html

It's not a precision instrument, but it will tell you if a cap is really bad while in circuit.  If I need to actually know an ESR value, I'll use my HP LCR meter.

[CMTan]

Hi All,
I have a ESR meter schematics which I redesigned.  The original is based on Luden's design, but being a design engineer I have to redesigned it after realising the flaws in the original design.  I have also raised several questions, for anyone who is challenged to think deeper into the design.

https://electronicsdesignfun.blogspot.com/p/esr-meter.html

Let me know if you have questions.

[m3vuv]

Firstly the chineese component testers will measure esr but the test voltage is to high for in circuit testing as has been pointed out,secondly why bother building the ludens esr meter that involves winding transformers,you can build the j diddy 5 transistor unit in less time it takes to wind the transformer,ive built both,the j diddy one works 100x better,its a no brainer imho.

[Shock]

Let me know if you have questions.

No lets not. Please discuss it in the actual project thread and not bump 9 year old threads elsewhere on the forum. https://www.eevblog.com/forum/projects/diy-analog-esr-meter-design/