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Measure in-circuit ESR using (LCR-T7) atmega component tester?

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harvie

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I've heard that it's possible to detect faulty electrolytic capacitors using ESR-meter without desoldering them from circuit. Will this work only with old single-purpose analogue ESR meters? Or can i measure ESR in-circuit even with the new popular atmel-based multifunctional testers like LCR-T7?

These cheap devices are very very cool when it cames to detecting standalone components:



But i am not sure how well they perform on components placed in circuit... Do you have any experience with this?
 

It could work if the tester can be configured to perform a low voltage impedance measurement and skips junction detection. The one-button automatic test concept has no room for configuration.
 

you must have a low voltage esr measurment to perform an in-circuit test
this meter (and his family) does not have it
on my repository, you can find esr meters to build yourself, that have this in-circuit capability.

**broken link removed**
 

Can you please elaborate on this? How does it work? The concept is same, but it uses lower voltage (like 0.2V ??) to prevent any nearby diodes and transistors from opening and starting to conduct?

Is there any way to set this up on these atmega meters using custom firmware? Or maybe simpe voltage dividers?
 

yes it uses low voltage (under 0.6V or even 0.2V some are around 0.1V) to measure the component esr.
then it has to amplify the resulting signal to be able to measure it.
and the atmega tester has no amplifier on its inputs so it cannot do this kind of measurments.
there would be too much changes to make it work, better build a dedicated in circuit esr meter
also you have to protect the device against some charged capacitors, and the atmega clearly does not have this feature also.
 

So i've found these two:

MESR-100 (42 USD)
Claims to use 15mV peak-to-peak

**broken link removed**



ESR-V5 (25 USD)
Can't get any information about used voltage

**broken link removed**

 

The difficulty as I see it, a lot of electrolytics are used as decoupling capacitors on a dc bus. Which means usually there may be several connected in parallel but distributed physically. If one goes high ESR, it may not be obvious if there are others connected in parallel that are working fine.

If ESR is critical enough to worry about, I think lifting at least one leg might be advisable.
 

one hint : esr meters that are delivered with crocodile clips are not to be used in circuit !
how can you clip the probes on a circuit without desoldering the capacitor ???
try one that are delivered standard with normal multimeter probes. (better one with 4 wires probes)

if you have $100 then buy a deree de5000, precise lcr meter that works in circuit (but that DONT discharge capacitors ...)
or make some esr meter like the one I gave in the link above.

for example this one : **broken link removed**
is really simple and has all you need (in circuit and discharges capacitor)
 

I just purchased one of these:

**broken link removed**

Only arrived yesterday, but for the price it appears to be a great little instrument to have handy.
Just the components to build one myself would surely cost far more, and the result not as good as this little gem.
 

Kripton2035 said:
one hint : esr meters that are delivered with crocodile clips are not to be used in circuit !
how can you clip the probes on a circuit without desoldering the capacitor ???
Click to expand...

You can plug different kind of probes in them :) The description says "in circuit". Cheap multimeters also usualy don't come with aligators, but i still buy them extra :) However having only crocodile clips surely gives us some hint about quality.

Kripton2035 said:
for example this one : **broken link removed**
is really simple and has all you need (in circuit and discharges capacitor)
Click to expand...

Why do you think this one discharges capacitors?? I don't think it's really good idea to use it on charged capacitor. At least when it's high voltage or high capacity.

Warpspeed said:
I just purchased one of these:
**broken link removed**

Click to expand...

This is one of the first ancestors of the LCR-T7 that i was originally asking about. Which means it's not usefull for in-circuit measuring. Main difference from LCR-T7 is that it has worse display, older firmware and cames without plastic case.
 


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