A scanning cannula for scanning an electrosurgical instrument for electrical insulation defects includes an elongated sleeve having a receiving end, an opposite exit end, and a passageway extending from the receiving end to the exit end. At least one sweeping contact is disposed in the passageway. A circuit in the sleeve is electrically connected to the at least one sweeping contact. A communication device is connected to the circuit to transmit signals from the circuit to a switchbox of a surgical instrument. An electrosurgical instrument inserted into the receiving end of the sleeve passes through the at least one sweeping contact, and any electrical defect of the electrosurgical instrument detected by the at least one sweeping contact is relayed as an error signal to the circuit, which communicates the error signal to the switchbox. The switchbox cuts current to the electrosurgical instrument and signals an alarm.
