Easy ESR meter for Electros

** Anyone who needs to check the ESR of a few electros can lash up a test rig in seconds - all you need is a bench audio generator and a basic scope or CRO as poms and Aussies call them.

Set the audio gen to about 100kHz (sine wave) use full level and connect the output across the electro under test - then connect the scope probes direct to the same cap, not the generator - this is important.

You should see a small voltage at 100kHz on the scope - say 2 to 100mV rms.

By comparison with known good electros of similar ratings, one can note the residual voltages and determine if a given electro is OK.

If you put a 1 ohm test load on the audio gen - you can easily find the output current and then use the voltage readings on the scope to get actual ESR values for electros.

Tests can be done while caps are still in circuit - but be careful to make sure they are fully discharged first !!!

.... Phil

Reply to
Phil Allison
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I didn't notice mention of any series resistor, and I have generators of both 50 ohm and 600 ohm output, but I guess if it doesn't blow out, it will be OK. !! Good tip.

greg

Reply to
GS

Or you can order a blue ESR meter kit from Anatek, solder it together and it gives you readings and a reference chart to determine good and bad caps. Much faster and convenient. Plus you have the fun and satisfaction of building it yourself.

BTW: there not that expensive

Shaun

Reply to
Shaun

I think Phil's point here was if you only wanted to check a couple of capacitors that you don't need to buy the kit.

Of course if you are servicing machines then an ESR meter is rather handy...(and we sell the Bob Parker design - Anatek BLUE ESR kit (rather shameless plug)).

There are also links at the bottom of my original ESR page for alternative testers including a $0.99 version (yes, that's 99 US cents - or 98 cents Canadian these days;-).

John :-#)#

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Reply to
John Robertson

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