In stray voltage investigations, it may be necessary to make several current measurements, including normal load currents and fault or leakage currents. The electrical current requirements of motors, lights, and other equipment will indicate whether or not the equipment is operating properly.

The current in an equipment grounding conductor can indicate a fault or leakage current. The total current requirements of a building, or set of buildings, can help determine the adequacy of the facility's electrical service. Monitoring the neutral current during periods of peak power usage indicates the neutral voltage drop. Neutral current measurements also indicate how well electric loads are balanced.

Clamp-on or recording ammeters are the proper instruments for many current measurements. Other types of ammeters must be installed in series. On occasion a current transformer must also be installed.