On Thu, 1 Dec 2011 11:16:20 -0800 (PST), pfm wrote:

On Dec 1, 11:38*am, Jeffrey Angus wrote:
On 12/1/2011 9:43 AM, Jim Yanik wrote:

Proper practice is to put the Device Under Test on the isolation
transformer,not the scope. leave the scope grounded.

I don't know why this is so hard for people to understand.

Test equipment is grounded. Period.

If your probe can't handle the offset voltage, you're using
the wrong probe.

If you're trying to measure something normally connected
directly across the utility power line, then use an isolation
transformer and you can ground any point in the device being
tested.

Use a solid ground jumper. Do NOT rely on the ground path
back through the scope probe.

Jeff-1.0
wa6fwi

--
"Everything from Crackers to Coffins"

Thanks. No question about the scope being grounded, no one suggested
otherwise. Tektronix maintain that floating measurements, taken in a
DUT powered by an isolating transformer, is bad practice.

Well they did want to sell expensive differential probes after all.

?-)