Abstract: A sensor circuit for detecting a ground fault in devices that eliminate or prevent static electricity and for producing appropriate alarm signals to indicate an undesirable ungrounded condition. In particular, the sensor circuit includes means for monitoring a ground-fault system by using a wrist strap monitoring circuit, a proximity monitoring circuit and at least one surface monitoring circuit. The wrist strap monitoring circuit and the surface monitoring circuits are used to detect the status of a grounding connection between an operator and/or a surface at a work station and a ground potential. The proximity monitoring circuit is used to determine whether an operator (or another person) is in proximity to the work station. A logic circuit means detects the status of the aforementioned monitoring circuits and selectively activates an alarm means if a fault condition exists.