On Wednesday 16 July 2014 06:16:36 Erik Christiansen did opine And Gene did reply: > On 16.07.14 04:27, Gene Heskett wrote: > > The only test tool I ever found that does a decent job of measuring > > this is called a "Capacitor Wizard", and sells for about 180-200 > > dollars on this side of the pond. Google for it. > > If the usage is there, it may well be worth the price, although a > useful but basic instrument can readily be put together. The circuits > which are thrown up by a "ESR meter circuit" google vary noticeably in > complexity, but are mostly pretty cheap to build. Since it only takes > a 0.1 ohm and 1 ohm resistor or similar from the junkbox to calibrate > them, some of them pretty much have to be good enough for identifying > dud > electrolytics, and even those which are marginal. > > I've only glanced through this article, but it doesn't look too bad, > and provides a good background for anyone needing an ESR primer: > > http://kakopa.com/ESR_meter/ > > But it admits to being a bit insensitive at the low end. This one talks > about 1 ohm being 90% of full scale. That would just about do me until > I found perfection: > > http://members.shaw.ca/swstuff/esrmeter.html
This one I would modify, with about a 4/1 stepdown toroid in the circuit where is says 250mv p-p, then use a micropower video speed op amp in place of the power hungry transistor, set for a gain of about 50. The stepdown tranny would also, by raising the load impedance on the paralleled buffer chip, the 74HC14, reduce its power draw, further extending its battery life. With those mods, I like this one better than the one below. A lot better. > > There are also circuits with transformers between oscillator and the > test capacitor, to lower the source impedance. That would be needed for > low ESR caps, I think. I'm tempted to add a cap and a step-down > transformer to an existing design which is otherwise appealing. I > bought a slab of Siemens RM4 ferrite core and bobbin sets for a song > the other day. Now I have a use for one of them. > > Here's one with better low ESR measurement potential: > > http://www.ludens.cl/Electron/esr/esr.html Looks good, but at 200mv output, it will tickle the socks off todays digital circuitry. The cap wizard still wins, at 85mv and 100khz. > > Who's found a better one? > > The thing is to know whether the circuit needs Low ESR caps, or > ordinary ones will do. If they are in a SMPS, or the power section of > a VFD, then bank on it. > > Erik Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS ------------------------------------------------------------------------------ Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
