Systems and methods are provided for monitoring operation of a circuit having a DC power supply, a load, and a switch element connecting the DC power supply to the load. The system includes a capacitive element coupling a first input node of a sensor element to a first interconnection node of the circuit between a first voltage supply terminal of the DC power supply and the load. The system also includes a grounding structure coupling a second input node of the sensor element to a ground plane isolated from the DC power supply. In the system, the grounding structure is positioned with respect to a second interconnection node of the circuit, between a second voltage supply terminal of the DC power supply and the load, so as to define a stray capacitance for carrying a transient signal resulting from the opening or closing of the switch element, which can be detected through the sensor element for monitoring the current switch state of the switch element.