The A6901 Ground Isolation Monitor is placed between a measurement instrument and its power source and acts as an indirect grounding device, allowing floating measurements to be made with operator protection. When the isolated voltage exceeds 40 V peak (28 V RMS), the unit interrupts the power to the instrument, connects it to the power source grounding system and sounds an audible signal. The device also tests for a functional ground between the power source and the instrument before the monitor goes into the isolation mode.