building an ESR meter

I'm interested in building an ESR meter and have some questions.

I've found two designs
Homo Ludens http://ludens.cl/Electron/esr/esr.html
Lawrence Glaister http://members.shaw.ca/swstuff/esrmeter.html

Initially, I'm drawn to the Ludens design.
Does anyone know where to get a small 400/20 transformer for this?

Any suggestions are appreciated.

Thanks

It kinda looks like one of the Xicon transformers from mouser...sorry I can't be of more help.

Hi

How about a little mains transformer?  120 V/6 V ?
By the way this is good meter.
http://www.peakelec.co.uk/acatalog/jz_esr60.html

Considering that the transformer is so uncritical (because it runs at very low power), feel free to use any small ferrite core you have on hand, as long as it has no air gap. Dead PC power supplies and old monitors or TVs are great sources for such cores. Do not use an iron core, because it would probably have far too much loss at 50kHz

Click to expand...

..power transformers are no good here - just follow the chap's advice and put 400 and 20 windings on a ferrite core transformer..

Jakob E.

I'm not sure why you need a transformer at all... ?

I would also be tempted to provide a scope probe output, to view the resultant waveform, or perhaps measure both peak and average results independently to also get a sense of ESL.

JR

Ptownkid said:

It kinda looks like one of the Xicon transformers from mouser.

Click to expand...

What about this one?
Xicon EI-19 Audio Transformers XFMR 500CT/16CT
http://www.mouser.com/Search/Refine.aspx?Keyword=42TM026-RC

500:16 is fairly close to 400:20

OOOPS
Those are impedance, not turns!

OK, we're talking about stepping down from very high impedance to 10 ohms and looking for a turns ratio of 400:20 (20). The impedance ratio is 20x20 = 400.
We're looking for a 4K:10 transformer.

42TM114-RC  Xicon  EI-19 Audio Transformers XFMR IMP 4.6K/20
http://www.mouser.com/Search/Refine.aspx?N=254428&Keyword=42TM114-RC&FS=True

Right?

http://ludens.cl/Electron/esr/esr.html said:

Do not use an iron core, because it would probably have far too much loss at 50kHz

Click to expand...

if you want to build this guy's design, take his advice, order the ferrite core and wind it yourself.  if you have a bunch of dead switching power supplies around and want to try transformers taken from there, go ahead.  or spend a lot of time looking for an off the shelf part.

ed

edanderson said:

http://ludens.cl/Electron/esr/esr.html said:

Do not use an iron core, because it would probably have far too much loss at 50kHz

Click to expand...

if you want to build this guy's design, take his advice, order the ferrite core and wind it yourself.  if you have a bunch of dead switching power supplies around and want to try transformers taken from there, go ahead.  or spend a lot of time looking for an off the shelf part.

ed

Click to expand...

Ditto---don't try to use 50-60 Hz magnetics.  Been there, done that, world of hurt.

But as JR says, why the guy decided to use a transformer anyway is at least questionable.  But a working design (as attested above) is worth following unless you didn't need to even look at it to begin with.

This one may be a good candidate.

http://alytus.auksa.lt/esr/
http://alytus.auksa.lt/esr/esr_meter_schematic.pdf

This is a classic and doesn't require any special parts.

Try this:

But how will you know if the capacitors test good for use in transformer circuits? :

JR

PRR, (with all due respect to your free time 8) ) could you possibly hack a little further into the circuit? Personally, I have a ZERO trust into a 062 driving a 190ohm-ish impedance. Do you think a 7555 (or a full 555) oscillator could be subbed? Or something else with little current draw..

"But how will you know if the capacitors test good for use in transformer circuits?"

its sort of like tubes that run a tube tester