Method for communicating a malfunction of a system for measuring speed and direction of rotation of a rotary shaft

A method for communicating a malfunction of a system for measuring speed and direction of rotation of a rotary shaft to processing means (13), said system comprising:

• a toothed wheel associated with said rotary shaft, called target (14),
• a magnetic field sensor (10, 10′), measuring values (K, A) of the magnetic field (B, B′, B″) generated by the passage of the teeth (T1, T2 . . . Ti) in front of said sensor (10′) and delivering a signal (S, S′, S″) to the processing means (13), said signal (S, S′, S″) comprising pulses (I) between a high state and a low state, each pulse (I) being representative of the passage of a tooth (T1, T2 . . . Ti) in front of the sensor (10′), and each pulse (I) having two predetermined durations, a first duration (t1) representative of a first direction of rotation of the target (14), and a second duration (t2) representative of the opposite direction of rotation of the target (14),
• wherein the detection method comprises the following steps:
• step 1:
• comparison by the sensor (10′) between the measured values (A, K) of the magnetic field (B, B′, B″) and predetermined threshold values (Aref, Kref) of the magnetic field (B, B′, B″),
• step 2:
• if the measured values (A, K) of the magnetic field (B, B′, B″) are below the predetermined threshold values (Aref, Kref) of the magnetic field (B, B′, B″), then
• step 3:
• generation by the sensor (10′), in a direction of rotation of the target (14), of a coding of the signal (S′, S″), representative of the measured values (A, K) of the magnetic field (B, B′, B″), by using at least one third pulse duration (t3) and at least one fourth pulse duration (t4) in order to communicate a malfunction of the system for measuring speed and direction of rotation of the rotary shaft to the processing means (13).