On Wed, Jul 16, 2014 at 4:27 AM, Gene Heskett <ghesk...@wdtv.com> wrote:
> Does this scope also measure "ESR"? That is an often overlooked > characteristic, but very real fault in electrolytic capacitors, much more > prevalent in the lower voltage stuff. The higher voltage stuff can > usually fix itself by re-welding the connections internally. Lower > voltage, under 150 volt stuff can't. > > ESR stands for equivalent series resistance. Its caused by poor > connections between the terminal leg you see, and the actual alu foil and > electrolyte soaked kraft paper that is the capacitor itself. > > 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. > > It uses an 85 millivolt signal to measure the capacitors resistance to a > 100 khz signal, and anything over 2 ohms was either bad or going bad next > week, change it. 85 millivolts so it didn't "fix" the bad cap. 100 khz so > it largely ignored the size of the cap until you were down to less than 2 > u-f. > > When I was the engineer fixing stuff at the tv station, it found bad caps, > in circuit, in digital circuitry, where the average cap is the size of a > pencil eraser, surface mounted, by the 3 lb coffee can full. It was the > single most valuable tool I had to keep about 20 DVC-PRO video tape > machines running well. > > That DVM that can measure capacitance, may well tell you that cap labeled > 47 u-f is actually 44 u-f, but it won't tell you its pure crap because its > internal resistance is well north of 10 ohms. > > [...] > > Cheers, Gene Heskett > Gene, Here's a really good ESR checker, for a whole lot less (if you buy it in kit form, takes less than an hour to solder and assemble): http://www.flippers.com/BlueEsr.html Mark ------------------------------------------------------------------------------ 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
