A method of diagnosing an operating state of a switching device, configured to be coupled to an electrical conductor and comprising: - separable contacts (24, 28) associated with the electrical conductor and controlled by an electromagnetic actuator comprising a coil connected to an electronic control device, which is configured to apply a control coil voltage (U BOB) across the coil, - sensors (Rsh, 50) configured to measure the coil voltage (U BOB) and a current of a coil current (I BOB) flowing in the coil, and wherein the method further comprises the steps consisting of: a) receiving an opening command from the switching device, the switching device initially being in a closed state, the opening command being received by the electronic control device; b) after receiving the opening command, command the electromagnetic actuator to open by means of the electronic control device; c) while the switching device is switching to the open state, measuring and recording the coil voltage (U BOB) and coil current (I BOB) values; d) calculating and recording values of a magnetic flux (Φ) passing through the coil, by integrating the recorded values of the coil current, the coil voltage and the values of resistance (R BOB) and inductance (L BOB) of the coil, previously recorded in the electronic control device; characterised in that the method further comprises the step consisting of: e) from the recorded values of magnetic flux (Φ) and coil current (I BOB), evaluate and record positions (x) of a core of the electromagnetic actuator as a function of a data table characteristic of the electromagnetic actuator, the data table being previously recorded in the electronic control device and defining a bijective relationship between the position (x) of the core, the magnetic flux ( Φ) and the coil current (I BOB). - separable contacts (24, 28) associated with the electrical conductor and controlled by an electromagnetic actuator comprising a coil connected to an electronic control device, which is configured to apply a control coil voltage (U BOB) across the coil, - sensors (Rsh, 50) configured to measure the coil voltage (U BOB) and a current of a coil current (I BOB) flowing in the coil, and wherein the method further comprises the steps consisting of: a) receiving an opening command from the switching device, the switching device initially being in a closed state, the opening command being received by the electronic control device; b) after receiving the opening command, command the electromagnetic actuator to open by means of the electronic control device; c) while the switching device is switching to the open state, measuring and recording the coil voltage (U BOB) and coil current (I BOB) values; d) calculating and recording values of a magnetic flux (Φ) passing through the coil, by integrating the recorded values of the coil current, the coil voltage and the values of resistance (R BOB) and inductance (L BOB) of the coil, previously recorded in the electronic control device; a) receiving an opening command from the switching device, the switching device initially being in a closed state, the opening command being received by the electronic control device; b) after receiving the opening command, command the electromagnetic actuator to open by means of the electronic control device; c) while the switching device is switching to the open state, measuring and recording the coil voltage (U BOB) and coil current (I BOB) values; d) calculating and recording values of a magnetic flux (Φ) passing through the coil, by integrating the recorded values of the coil current, the coil voltage and the values of resistance (R BOB) and inductance (L BOB) of the coil, previously recorded in the electronic control device; characterised in that the method further comprises the step consisting of: e) from the recorded values of magnetic flux (Φ) and coil current (I BOB), evaluate and record positions (x) of a core of the electromagnetic actuator as a function of a data table characteristic of the electromagnetic actuator, the data table being previously recorded in the electronic control device and defining a bijective relationship between the position (x) of the core, the magnetic flux ( Φ) and the coil current (I BOB).