Quote:
Originally Posted by TinCanAlley
I was just going to touch the tip of the probe to the hot side and leave the ground clip disconnected.
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Good! I just thought that I should pass on a lesson that I learned the hard way.

Early 'scopes that I used (Heathkits mostly) were not grounded through the power cord, so I had quite a surprise when I connected my first *grounded* Tek scope to a hot chassis radio!
You likely introduce a bit of error by single tip probing, because the scope earth ground may be a slightly different voltage than the "ground" side of the line. The *best* measurement would be obtained by the 2 tip/2 channel "differential" method, described by dtvmcdonald in a post above. Accurate, and safe for the 'scope
jr