Diagnostic element for validation of bolt detection of a guard locking switch in a static state

An industrial locking switch includes an inductive sensing circuit that uses a non-contact technique to detect when the switch's locking bolt has transitioned to the lock position. The inductive sensing circuit can comprise an inductive coil, a capacitor, and a converter that converts a frequency of a current signal through the inductive coil to a digital frequency value. A controller detects when the locking bolt has advanced to the lock position by monitoring the digital frequency value for frequency shifts indicative of a disturbance of the induction coil's magnetic field by the locking bolt. To validate operation of the inductive sensing system without requiring actuation of the locking bolt, a diagnostic switch connects a diagnostic capacitor to the inductive circuit to simulate the frequency shift caused by the locking bolt, and the inductive sensing system is validated if the expected frequency shift is detected.