Theory Of Operation

This diagnostic compares the output signal of the sensor to threshold values of normal operation. When the signal is out of range the diagnostic will be considered failing. The sensor is mounted next to the gate select actuator to detect a linear movement of the spool. For this purpose a permanent magnet is mounted on the spool which is moved over a complete travel stroke. The magnet position generates a saturation area in the internal ferromagnetic core of the sensor which is transformed to an output position signal. The sensor provides an output signal with Pulse Width Modulation (PWM) at a fixed frequency and duty cycle proportional to the spool position of the actuator. The PWM duty cycle ranges between 10% and 90%.