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My "guess" is this digi-bridge instrument is just a high accuracy -component out of circuit- only Wien bridge based device. Most all ESR meters out there currently are non-Wien bridge based and use a high frequency test signal (~~ 100Khz sine wave) to effectively measure the A.C. impedance of a capacitor. Also, they only output ~~ 100mV or so in that they don't activate any PN on NP semiconductor junctions; another reason they are so handy for in-circuit testing. Yes the ESR maybe a fraction off in-circuit VS out of circuit but you're looking for a gross discrepancy when using these ESR meters. Take a 100uF cap which measures say 50 ohms and the spec should be less than 0.1 ohms; light bulb event; Houston we have a problem; LOL).
So it's not surprising how you got misleading results on the tested caps in-circuit VS out of circuit on this "digi-bridge" tester; expected behavior??? If I'm wrong, others will "correct" me.
Tom (PK)
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