30A campground receptacle testerby forum member searching
To test the 30-amp 120-volt outlet use a 30-amp Male to a 15-amp Female reducer. Available at Camping World or other RV supply houses. Two versions are made, round and the dog-bone. The Voltmeter and the 3-Wire Circuit Analyzer plugs into the 15-amp Female end of the reducer.
This little 3-way splitter comes in handy for checking the 30-amp service. Plug in the Voltmeter and the 3-way Circuit tester at the same time. I also use it to check the 30 and 50-amp outlet under load.