From Webshed
Revision as of 19:52, 22 December 2011 by WikiSysop (talk | contribs) (Created page with " == An Equivalent Series Resistance Meter == Some time ago I was trying to repair a switched mode power supply (SMPS) in my oscilloscope. I'd been quoted £800 for a new PSU, so…")

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

An Equivalent Series Resistance Meter

Some time ago I was trying to repair a switched mode power supply (SMPS) in my oscilloscope. I'd been quoted £800 for a new PSU, so trying to fix it first was well worth my while. It's pretty common for electrolytic capacitors to develop faults in an SMPS; specifically they develop an higher than normal internal resistance. So while the capacitor may hold a charge and measure as the correct capacitance, it will not behave correctly in a filter or PSU circuit. Suspecting the capacitors, and not having a way to measure their series resistance, I set out to design and build an ESR meter.

The ESR of a large high voltage, high capacity electrolytic capacitor should be fractions of an Ohm, smaller capacitors have ESRs of a few Ohms typically.