Sarah, sorry to take so long answering your questions about the monitor I used to use to first monitor the electrical box at the campground and then to monitor the incoming electric inside my rig. You need two items:
Prime Products 12-4058 AC Power Line Monitor
Camco 55233 30 amp male/15 amp female electrical adapter.
Both are available at Amazon.
These things saved my rig more than once: campground had low power so would have been in a brown out situation that could have burned up my AC, frig, etc. Low incoming electric from campground also a brown out situation. I kept it plugged in all the time inside the rig. If it dropped below 110 I shut something down or turned on the generator.