Did someone say they wanted VA, and HZ?

MrWizard wrote:
I think you could use one meter
But you need to run both hot thru the current transformer, (in opposite directions) to keep the phasing so they don't cancel each other

Need to check on that to be sure of the correct wiring

The most useful in my opinion would be two meters, one for each leg. You obviously can't monitor the individual leg voltages and currents simultaneously with a single meter.

If you have the two hots going through the current transformer in opposite directions, you would read the sum of the current on the two legs when connected to a proper 120/240V 50A supply, but the difference between them when connected to a 120V supply (say with a 30A to 50A adapter or, at least in some cases, when using the built-in generator). You'd get some not to useful intermediate reading if you ever encounter a campground socket wired with two of the three phases of a 120/208V three phase supply, a not especially common setup but one that is still code compliant.

If one puts the two hots in going the same direction, the difference in current between the legs would be read with a 120/240V 50A connection, and the total current when hooked up to a 120V supply with an adapter or whatever, and some other not very useful intermediate reading with a three phase supply.