AEMC AN-1 Leakage Current Tester Meter and Probe generates a momentary grounded artificial neutral to allow the measurement of fault currents on ungrounded three-phase systems. The Artificial Neutral is grounded intermittently through a relay driven by an internal electronic timer. This periodic grounding technique performs three functions limits the possibility of insulation faults within the instrument, allows for better discrimination of actual fault current and limits instrument overheating. Relay closure time is switch selectable, Fast (0.5 seconds) or Slow (2.3 seconds), so that the ground fault clamp can be used on a meter with either an analog or digital display. An internal buzzer, also driven by the relay, is activated each time the neutral connection is grounded. Three LEDs, one for each phase, show the presence of each of the three phases prior to measurement. A fourth green LED indicates that the instrument is operating.