Quote:
Originally Posted by Radio Wrangler
You may find it has EMC capacitors bridging the scope's (now disconnected from mains ground) common and the line and neutral of mains. At the high frequencies you're trying to float the thing at you may have enough current in them to create some drama.
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Yes - unfortunately, which is why I qualified my suggestion with the words "You might be able to get away with..."
High-side drivers are a pain! For all high-side drivers I've needed, I have driven with a transformer. And on the same transformer, I have had an identical winding to drive the low side, even if not strictly necessary. At least by doing this, I can be certain that the difficult-to-assess high side is the same as the easy-to-monitor low side.
If you cannot float the scope, then float the unit-under-test. I suggested operate from batteries, for maximum isolation from earth (including capacitively). Much better than using a bench power supply.
Hugo's solution, that of buying a custom 'scope, is going to be the best (when Tektronix decide to make a piece of test equipment, they do it well). But I have no experience of this.