Just clampon to the positive refer wire to measure the refer draw.
These tools are invaluable for the DYI RVer, especially for determing battery and AC loads. The clampon ammeter measures AC volts/amps, DC volts/amps, resistance, frequency (useful for checking a gen) and temperature. The accuracy is more than adequate for RV usage. The line splitter allows for easy measurement of AC amps for any plug in appliance. The female plug is on the bottom and the 2 loops allow for measuring 1x and 10x amps (useful for measuring small AC loads). About $75 for the pair. Check that any clampon meter you purchase can measure DC amps as they are less common than ones that measure only AC amps.
