....transformer to reduce to 110v for the DRO?
Preferred way, actually. 'Future proofing" route.
Because it works the same across (any) two legs of 3-Phase as across (the only) two legs of 1-P.
One CAN utilize a 220/230/240 VAC primary to a 110/115/120 VAC
center-tapped secondary with the centre tap Earthed as well. Not uncommon for wet environment corded power tools.
That gives you the 120 VAC you need across the "ends" but each is only 55---60 VAC above ground instead of one Earthed and the other at the full @ 120 VAC above ground.
BEFORE. you do
anything further...
LOOK at your DRO's manual and/or PSU.
If a "globalized" unit? It may have:
EITHER
- a manual selector switch for 120/240 (nominal) as AC input right on it or on its power supply..
ELSE
- a PSU that is automagically able to run the DRO's modest load off any incoming 50-60 Hz source from 80 or 100 minimum to 240 or 250 VAC maximum.
No pre-selection switch required.
See laptop 'puter "brick" with IEC cords, some fax/inkjet/laser printers..
A DRO usually needs less power than a laptop, so flexible power might already "be there" to simplify the maker's need of stocking more than one flavour of goods, North America/Japan market, rest of the world.
2CW