ESR meters again

[Jules Richardson]

I seem to be accumulating a pile of things with faults that are most likely down to dodgy capacitors, but my homebrew ESR meter's one of those things that is still in deep storage back in the UK. So...

1) I know that there was a thread a few weeks ago about ESR meters, and someone suggested one that was being sold on ebay - I think that listing's gone, but the site seems to be awash with others (all via China) which I believe are exactly the same product (e.g. http:// tinyurl.com/ces3y7m). They all show a capacitor hooked directly to the meter, though - so can anyone confirm that this meter is suitable for in- circuit testing? (typically I think meters output a sine wave around 100kHz with an amplitude below that which will trip TTL logic gates, do they not?)

2) Any other recommendations for a cheap meter? I really don't need inductance, transistor testing etc. as my DMM does that anyway ,so just plain ol' ESR will do.

3) Any recommendations for schematics for a DIY meter? I think I've got at least one moving-coil meter in the junk box, and a few op-amps of various types. I don't think I've got the schematic for the "in-storage" meter that I built any more. There are quite a few schematics available via google, but I don't know if any of them are any good or not...

cheers

Jules

[Dave Plowman (News)]

The cheap ESR and so on one off Ebay is rather better for basic transistor checking than any of the DVMs etc I have - you don't need to identify the transistor first. Just test it and the meter tells you the pin out, NPN or PNP, as well as gain etc. Very useful, IMHO.

It seems to work on in circuit caps as well as my other ESR meter.

[meow2222]

Amazon £12-15, test L,C&ESR,R,etc

NT

[Graham.]

This looks like the one mentioned.

It doesn't mention in-circuit ESR testing but I can't think of a reason why it wouldn't work in most cases.

[Andrew Gabriel]

I repair lots of things, but I haven't yet needed an ESR meter. To test, I simply parallel up a new capacitor, and see if that fixes the issue.

[Jules Richardson]

Hmm, OK if there's the physical space to do so, or you have suitable spares (and know that they're good!), and the item doesn't use too many, and that the item can easily be tested without lots of reassembly etc.

I've got by without a meter for a few years now because all the cap faults I've had in things have been obvious ones (leaks, bulging cases, circuit [mis]behaviour pointing to a particular one etc.) - but just lately I seem to have accumulated things where a meter would make life a lot easier.

It's certainly not something that I'd use particularly often (and so naturally don't want to spend a fortune on, either!) - but it'd be useful to have one around.

cheers

Jules

[Dave Plowman (News)]

Not much use with tantalum which can fail short circuit. ;-)

Checking a suspect cap with an ESR meter is so much quicker than by substitution, etc. I'd say it's one of those things you may not miss if you've never had one.

My Bob Parker kit one was pretty expensive, but still paid for itself. They're a lot cheaper now with even cheaper alternatives.

[Andrew Gabriel]

I didn't say by substitution - I usually just touch the leads of a new one against the existing one's leads. If it's a mains circuit, I might temporarily solder it to the existing cap's solder pads on the underside of the circuit board so I'm not holding it.

[Theo Markettos]

There's a variety like that. Most of those on ebay have a simple pin header to connect the cap - if it's in circuit that means it's awkward to connect test leads. The leads will have some resistance of their own, and it would be nice to be able to null that out. Of course you can do it manually (just subtract in your head) but easier if it does it for you.

This one:

has screw terminals, but no transistor test and somewhat byzantine modes. OTOH it does bother to put pillars for the LCD which most of the others don't. It's also not clear if it will work with a PP3 battery out of the box. Some more details on the calibration procedure here (think this is the same software):

Ah, interesting. This one:

which has the same PCB layout as above, uses a stc12le5a60s2 microcontroller, and: have some info about the algorithm if you translate from Chinese (though quite hard to follow)

Aha! This:

has an attachment with the schematic and the source code.

I'm not sure it helps that much, but at least allows you to see what it's doing.

Theo

[Theo Markettos]

More digging. Apparently the three-input type marked 'Booster edition Transistor L/C ESR tester' on the PCB are all knockoffs of a project by Markus Frejek based on an ATmega168. Another thread on them:

Karl-Heinz Kuebbeler has extended it (in German):

Theo

[mark]

+1