ESR Meter confusion

I just picked one cheap and cheap or no shipping from China. There may be program differences. Non of them measure high values of capacitance. Mine is the component testor. Most devices included in testing.

Greg

You can't beat free.

Works for 30 days before some features get disabled, but looks like the ESR may still work after that. I played with an earlier version years ago and found it very useful for ESR testing.

It uses a PC sound card for testing.

It requires a stereo microphone input. Some computers have mono microphone input and won't work. I had a soundblaster USB at the time.

There's discussion of sound cards on their site.

Might be worth a look. YMMV.

There are many of those "$5 including shipping" component testers on ebay and aliexpress that you can try, they automatically determine the component you plug in the ZIF socket and when it is a capacitor they also indicate the ESR. This is a nice toy for the low-budget hobbyist.

Do you have a 'scope and function generator? How much accuracy do you need/ want?

George H.

those things are quite handy. They test a lot more than caps of course. Plenty of limitations but a good choice for the hobbyist, and quite useful for the non-hobbeast.

NT

If he has a scope, he doesn't need an ESR tester; just scope the ripple.

One old TV repair trick was to in-circuit parallel a suspect cap with a good one. If that fixed the set, leave them both in.

ESR testers are a sort of amateur cult thing. Most cheap and many not cheap L/C and ESR meters are awful.

Fun: measure an inductor with several different L meters.

They're good enough to tell a good cap from a dud. I've found that useful. It may be worth bearing in mind I've worked on kit from every decade back to the 1920s.

If you want inductors tested over a range of currents you'll need more than a basic tester. Coils of wire are more complex than they appear.

NT

Ah, well, no, never a good idea as the old cap was likely leaky and as such slowly turning into a resistor... Ever felt the cans on those old electros? If the can was warm/hot then the cap was assumed bad. Warmer than the chassis that is.

Bob Parkers ESR kit is still outstanding - I've lost count how many we sold after the 1,000 mark passed 15 years ago. We still sell a dozen or so a year. And continue to use one in our own service shop.

John :-#)#

I was going to tell him your trick of voltage step into a cap and reading ESR off the step part of the response. That works for certain values.

I'm not sure I always trust our expensive LCR meter. There's this old Boonton radio Q-meter on the equipment shelves... It worked last time I turned it on. (Good for HF stuff)

George H.

If you have a square wave generator and a scope, that test is a lot more believable than a number on some ESR meter. It suggests ESL too.

Right. I think when I tried it I used the edge from my function generator and that's not as fast as it could be.

George h.

I used my old B+K analog function generator for that pic. It doesn't need to be super fast. The scope sweep was 4 us/cm.

w2aew has a very good explanation of measuring ESR with a scope and function generator.

Cheers

Not very good. For the "bad" cap, he's not properly separating the ESR from the capacitance.

Heathkit made a nice LC tester that used a Magic Eye tube to show results. One feature of this meter was a Power Factor and that was handy for seeing how well electrolytic caps performed under load. I don't bother any more because most modern caps with a good name brand are much better than the oldies so we usually just replace electros (and the rest) in tube equipment then troubleshoot.

John :-#)#

Yup - but in fairness he does explain how to. And if you're just looking for bad caps, it doesn't matter which caused the problem, ESR or loss of C.

NT

te:

The question is whether the meters are awful or if the parallel and serial resistances are a little too distributed to be usefully characterised by a measurement at a single frequency.

Inductors have series resistance in the windings, and a parallel resistance due to the current inducted in the core material (if they have a core, whi ch most do). The series resistance in the windings eventually increases wit h frequency because of the skin effect.

All great fun to do properly, but who has the time, or the multi-frequency impedance bridge ...

OK, I'll have to try it again sometime. I think I used my Rigol FG.. may not be as snappy as the wavetek.

George H.

Hmm... it's not that bad. You should be able to get R and C for the bad one.

GH