ESR Meter

[john page]

Hey neat. I gotta try this. Thanks.  john

>From: Bob Nickels <ranickel at MWCI.NET>
>Reply-To: Bob Nickels <ranickel at MWCI.NET>
>To: HEATH at LISTSERV.TEMPE.GOV
>Subject: Re: ESR Meter
>Date: Tue, 6 Nov 2001 20:45:25 -0600
>
>I agree wholeheartedly with Mike and others about the value of ESR testing
>of
>electrolytic capacitors.  Once you try it, you'll be a believer too!
>
>Not to detract from the excellent designs that are recommended - but it's
>so easy
>to rig up your own ESR measurement circuit, there's no reason not to give
>it a try
>yet tonight!
>
>All you need is any old oscilloscope and some kind of signal generator that
>cover
>the "range of interest".  By that I mean a frequency where the cap under
>test will
>have a low reactance it is "good" (i.e. low ESR).   Connect the output of
>the
>signal generator, the input of the o'scope and a pair of test leads all in
>parallel - that's it!   With the probes disconnected you will see the
>output of
>the generator.  Now if you touch the probes to a good capacitor, the
>generator
>output will be shunted by the capacitive reactance and the scope display
>will
>become very low in amplitude.   Check a few old caps and you'll quickly see
>the
>difference - many will only be able to reduce the signal by half, or even
>less.
>The amplitude of the signal displayed by the scope is proportional to ESR.
>
>A neat trick:  limit the amplitude of the test signal to < 0.7 volts and
>you can
>test capacitors in-circuit without biasing transistors on.! The service
>tech who
>developed this method claims he reduce his repair time on consumer
>electronics by
>over 50% and it's a good way to use some old test equipment.  I just keep
>Ch 2 of
>my dual-trace scope hooked up and simply switch to that channel when I want
>to
>measure ESD.   Good luck with this simple method of visualizing ESR.
>
>73, Bob W9RAN
>
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