Hi,

I've been following this very long thread and waiting for it all to come
together for me.... No Such Luck.
I don't own an o-scope and haven't used one since school but would very
much like have one. So please forgive me if this comes across as a
stupid question. But I just don't understand.

Isn't the scope's probe isolated from the AC supply?
Isn't / shouldn't the scope's signal ground be isolated from the scopes
earth ground? After all, the signal ground should simply be a reference
and could be placed anywhere. (Right?)

If the above is true (which I suspect it isn't) how could there be an
appreciable potential anywhere that might be dangerous?

Aren't we just measuring a potential from the scope probe to the scope's
signal ground, irrespective of the supply of either the scope or the
item under test?

Again, I'm afraid someone will try to tell me how stupid I am but, this
is really bothering me. Could somebody please fill me in?

Thanks,
Erik