[Radioroslyn]

With out a isolation transformer you can measure the ac voltage from the chassis to earth ground. Plugged in one way you will read 120ac and the other you will see a small ac voltage. If you have it plugged in with small ac voltage at the chassis you will be OK to connect your test equipment to it. ALWAYS PLUG IT IN IN THE SAME DIRECTION!!! If you want to double check measure the ac voltage between your chassis and your test equipment. Just make sure that you DO NOT have 120vac between the chassis and anything you connect to it.
Flame suit on
Terry