On Wed, 22 Apr 2015 19:03:41 -0700 (PDT), Ivan Vegvary
wrote:

Okay, I know that electrolytics are the most likely to fail.
However why do the manufacturers of ESR meters discuss ONLY
electrolytics? do ceramics etc. not have an "equivalent series
resistance"? Can they also be checked?

You can check any type of capacitor. However, electrolytics are one
the few types of capacitors that have a liquid electrolyte, which is
subject to decomposition, contamination, leaking, outgassing, and
corrosion. The other liquid dielectric is the wet slug tantalum,
which is considered a health and fire hazard. Solid dielectric caps,
such as ceramic, film, mica, etc don't have these problems.
Unfortunately, they have other problems. Film caps fall apart
internally. MLCC (multilayer ceramic caps) have a very thin brittle
dielectric which easily cracks when stressed or thermal shocked. Some
film caps are hygroscopic and change value when the case is cracked.
Most of these failures are catastrophic and are easily seen with a
capacitance meter. Only the electrolytics are able to change ESR
without a corresponding change in capacitance. Therefore, the ESR
meter targets electrolytic capacitor failures, while a capacitance
meter works well enough for the other capacitor types.

Note that an ESR meter is also used for battery testing, but those
tend to be rather specialized. For example, capacitor ESR meters run
at 100KHz, while battery testers run at 1KHz.
http://batteryuniversity.com/learn/article/how_to_measure_internal_resistance


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Jeff Liebermann
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