I use one of these RV AC VOLTMETERs plugged into a handy 120VAC receptacle so I can get a good glance at the AC VOLTAGE LEVELS. The SAFE ZONE is printed in GREEN.
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If the METER is showing just under the GREEN ZONE I will use my MULTIMETER to measure the AC VOLTAGE to get an more correct reading.
This is a good chart to use to make measurements using a MULTIMETER at the camp ground pedestals for the 50A and the 30A readings.
50AMPS
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30AMPS/20A/15A
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Another good test is use one of those inexpensive CIRCUIT TESTERS (LOWES-WALMART-AMAZON).. The problem with these is they only plug into the 120VAC 15A/20A RECEPTACLES so if you want to the measyre the 30A or 50A side of the pedestal you will have to to use the standard RV 50A and 30A ADAPTERS.
Burning up your appliances can get expensive...
Roy Ken