Capacitor Wizard (ESR Tester) Meter Movement
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From: behindontaxes on 4 Mar 2010 12:54 I got this part: http://shop.midwestdevices.com/product.sc?productId=3&categoryId=1 when I really should have been looking for this complete assembly: http://midwestdevices.com/Brochure_Blowup.html The movement is a 1ma FS 50 ohm device. Can I build a complete do-it-yourself ESR tester from this meter movement? Thanks for reading!
From: John Fields on 4 Mar 2010 12:59 On Thu, 04 Mar 2010 11:54:25 -0600, "behindontaxes(a)xemaps.com" <behindontaxes(a)xemaps.com> wrote: >I got this part: > >http://shop.midwestdevices.com/product.sc?productId=3&categoryId=1 > >when I really should have been looking for this complete assembly: > >http://midwestdevices.com/Brochure_Blowup.html > >The movement is a 1ma FS 50 ohm device. > >Can I build a complete do-it-yourself ESR tester from this meter >movement? --- Sure; in the same way that you can build a car around a speedometer. JF
From: Jon Slaughter on 4 Mar 2010 14:22 behindontaxes(a)xemaps.com wrote: > I got this part: > > http://shop.midwestdevices.com/product.sc?productId=3&categoryId=1 > > when I really should have been looking for this complete assembly: > > http://midwestdevices.com/Brochure_Blowup.html > > The movement is a 1ma FS 50 ohm device. > > Can I build a complete do-it-yourself ESR tester from this meter > movement? If you really wanted... http://ludens.cl/Electron/esr/esr.html The idea is pretty simple. A discharged capped will have an ESR with effectively no initial voltage and therefor will act as a voltage divider with a known resistance. By measuring the voltage ratio you know the ratio of resistances. For an ideal cap the measured voltage would be 0. For a reading of 1/2 the voltage would mean that the ESR has the same value of the known resistance. You can play around with this idea to get more precise measurements. It is not a great method because as soon as a voltage is applied the capacitor charges and skews the result. Using an AC wave and for large caps it is not too bad. Another method that is similar is to load the cap in a delta or wye configuration or use a wheatstone bridge.
From: Jon Slaughter on 4 Mar 2010 14:29 Jon Slaughter wrote: > behindontaxes(a)xemaps.com wrote: >> I got this part: >> >> http://shop.midwestdevices.com/product.sc?productId=3&categoryId=1 >> >> when I really should have been looking for this complete assembly: >> >> http://midwestdevices.com/Brochure_Blowup.html >> >> The movement is a 1ma FS 50 ohm device. >> >> Can I build a complete do-it-yourself ESR tester from this meter >> movement? > > If you really wanted... > > http://ludens.cl/Electron/esr/esr.html > > The idea is pretty simple. A discharged capped will have an ESR with > effectively no initial voltage and therefor will act as a voltage > divider with a known resistance. By measuring the voltage ratio you > know the ratio of resistances. > > For an ideal cap the measured voltage would be 0. For a reading of > 1/2 the voltage would mean that the ESR has the same value of the > known resistance. > You can play around with this idea to get more precise measurements. > It is not a great method because as soon as a voltage is applied the > capacitor charges and skews the result. Using an AC wave and for > large caps it is not too bad. > > Another method that is similar is to load the cap in a delta or wye > configuration or use a wheatstone bridge. BTW, the whole idea is to find a way to distinguish --R---C and --C-- (or when R = 0 in the first case) For R to matter current must flow "through" the cap so there is a voltage drop through R. Hence rapidly charing and discharging the cap(much faster than it's time constant) will allow you to effectively ignore C and then it becomes simply a resistance measuring problem. Alternatively you can charge up the cap and note the deviation between the ideal curve(R = 0) and non-ideal(which changes the time constant). Since when the cap is completely charged no current flows and no voltage drop on R while initially there is a voltage drop across R. This method doesn't work in circuit since.
From: Bob Monsen on 5 Mar 2010 11:53
<behindontaxes(a)xemaps.com> wrote in message news:Xns9D31834BB4AA1behindontaxesxemapsc(a)127.0.0.1... > I got this part: > > http://shop.midwestdevices.com/product.sc?productId=3&categoryId=1 > > when I really should have been looking for this complete assembly: > > http://midwestdevices.com/Brochure_Blowup.html > > The movement is a 1ma FS 50 ohm device. > > Can I build a complete do-it-yourself ESR tester from this meter > movement? > > Thanks for reading! You spent $45 on a meter movement? Send it back. You can get them without the extra paint for $10. http://www.elexp.com/tst_mamo.htm Regards. Bob Monsen |