Are these cheapo ESR meters truly "in-circuit"?

[Delta]

Has anyone got any experience of these meters? eBay auction: #191827984796

Do they use a test voltage low enough such that they don't turn on any semiconductors and thus can be used without lifting a leg of the cap?


There's also a plethora of those ATMega328 based multi component testers, can they be used to test ESR in circuit?

[tggzzz]

Regardless of the voltage, any "in circuit" tester will be affected by surrounding components.

For one example, consider power rail decoupled by two 100uF tantalums electrolytics and ten 100nF ceramics. If you measure across the leads of one tant, what will the ESR be?

[Delta]

Regardless of the voltage, any "in circuit" tester will be affected by surrounding components.

For one example, consider power rail decoupled by two 100uF tantalums electrolytics and ten 100nF ceramics. If you measure across the leads of one tant, what will the ESR be?

0.08263ohms?

Yeah, I'm aware of the limitations, and parallel paths will always be an issue.   I'm just looking for something that will give a quick indication of electrolytics in SMPSs above "it's not bulging so it's probably OK"!

Maybe I should have phrased the question "do these use a voltage low enough that they won't blast through the diode bride and read zero ohms even if the cap is FUBARed?"