Hi I'm thinking of buying a current ranger but wanted to see if there is a way to measure voltage and current with an oscilloscope without dangerous ground loops. I am trying to measure a floating DUT with a floating power supply using a grounded non isolated oscilloscope.
I believe the naive approach - measure the current ranger with one probe and then measure the voltage over the DUT with another probe - produces a ground loop as the scope ground leads are at different potentials (DUT+ and DUT- respectively).
Would it work to swap the leads of voltage probe so the ground lead is at DUT+ and the measurement side is at DUT-? No right? Because the current ranger sense - is different from the current ranger load output, right?
Or do I need a differential probe to measure both the current and DUT voltage at the same time?
I would recommend doing a dual measurement using a certain trigger generated by the DUT (like a digital HIGH on a pin when it wakes up).
Then you use that to synchronize the two measurements.
Otherwise I would recommend using a differential probe since the oscilloscope is now the common ground reference to the two current+voltage measurements.