The Tektronix A6902 does not provide a differential input (unless two channels are combined) but has complete galvanic isolation; it effectively has one high impedance connection and one low impedance "ground" for each channel. There are some specialty DSOs like the Tektronix TPS2000 which provide the same thing on each of their inputs; they are convenient for safely making primary side off-line and power line measurements.
So what are you saying is, basically A6902 turns an ordinary 2 ch scope into this ?
Illustration from Tek's handheld scope manual.
That TPS2000 is interesting, just knew it, quite an unique scope.
A high voltage differential probe has a differential input with two high impedance connections but does not provide galvanic isolation; it still relies on a third common "ground" connection somewhere.
Yeah, this is my confusion as well, as I own a low voltage differential probe Tek P6046 that needs its common ground to be connected DUT, while these typical HV differential probe doesn't have any.
Like below photo on the HV diff. probe, only two differential points needed, why it doesn't need the common ground ?
If you used a differential probe on an isolated input, then it can fail do to the lack of a ground connection which allows the common mode voltage to drift out of range.
What kind of situation or better an example case for this ?
David, thanks a lot for the explanation.