GFCI plus 2-prong plug adapter as poor man's isolation for Oscilloscope?

[capt bullshot]

What about running my digital scope (Siglent 1104X-E) off of a UPS running on battery (with AC unplugged)?
Wouldn't this give me the equivalent of a (literally) battery-powered scope?
Would there be any problems with the lower end UPS's having non-true sine wave (and potentially noisy) output voltages?

The scope seems to consume ~33W of power. So, even a small UPS with a 12V 9Ah battery should give almost an hour of runtime. This should be plenty, particularly if I plug/unplug the UPS only when making measurements. Presumably I could install a triple-pole switch to isolate hot/neutral/ground when switching to battery power...

Doing so doesn't make any difference to lifting the ground regarding your personal safety. So if you _really_ want to float your scope and _know_ what you're doing, simply cut the earth wire. Nothing else required, and adding stuff like your UPS setup creates a false feeling of beeing safe.

[Jeroen3]

The problem with pulling the ground wire from your scope is that you create an implicit 50V (us) or 115V (eu) ~1mA AC source with regards to earth, or DUT's with the plug reversed.
This means wherever your attach ground in your circuit, if that circuit is connected to mains, there could run a few mA of AC current trough it from power supply to power supply.
This is what kills boards and screws up your measurement since the frequency can be 50/60Hz or whatever else is used in those power supplies plus noise on the grid.

I hear you thinking, but what if I don't have grounded sockets? Then you use equipotential bonding. This forms automagically when using a grounded terminal strip. All "grounds" are connected, but it isn't "earth". This is a risk in itself, but sometimes it is done. Read some literature about this before you even consider it.

Running the scope on battery is the best of the worst methods. But you'd have to keep in mind that all exposed metal is scope ground and can't be touched anymore. Including the USB and GPIB plug and probe cal.
And you still don't have inter channel isolation.

Can you do it? Yes.
Will it work? Maybe, depends on what you measure.
Is it safe? No.
Does a GFCI make it safe? No.

What is safe? HVP70

And:


Test it!
Pull the ground wire. And then take your multimeter in milliamps AC to make the ground connection. What do you see?
This will run through your DUT when you pull ground.

[Fungus]

But what about removing the grounding pin from the oscilloscope (e.,g., by using a 3-to-2 pin plug adapter) and then plugging the two-pronged plug into a GFCI? (in practice since my workbench is in the basement, all my outlets are GFCI protected anyway).

No!

The bad electrons don't come along the 'scopes power cable, they come from the DUT when you clip the ground probe onto it. Your GFCI won't make the slightest difference to safety.