Here is what you do to not have to be poking around where you should'nt be with small meter leads..
When you first pull up at the camp ground pedestal just plug in this setup first which will read the correct 120VAC reading that is good for your trailer and will also test the proper grounds. If either of these two simple test are bad DON'T PLUG in your trailer.

These are two adapter cords that will adapt a 30A and 50A pedestal service connection down to a 15A 120VAC connector.

Then plug one of these KILL-A-WATT meters into the 15A end of these 30A adapter cable.

Then plug in these 120VAC Circuit Tester into the KILL-A-METER.

When you connect this setup to the 30A Service Adapter or the 50A service using the 50A Adapter and the 30A Adapter then you will be to read the proper 120VAC available to power up your trailer. Also the 120VAC circuit tester will tell you the connections are properly grounded by the CORRECT test lights being lit up.
If either of these two conditioners are not right then DO NOT USE their camp ground service connections. GO ask for a different site.
This is what I do when I show up at the camp grounds before I plug in my trailer. I have to admit I sometimes forget and just go hookup but when I see burn marks and nastly looking plugs I most definitely will test the service connections...
Roy Ken