magnetic rotational speed sensor

SPH3A0 series of positive and negative rotation speed sensor is tested by Hall principle. Two pcs of magnets with opposite poles need to be fixed on the axis and wheel (the two pcs of magnets are symmetrically distributed, and N pole of one magnet should be fixed facing the sensor and S pole of another magnet should be fixed facing the sensor), and fix the of the arrow on the sensor?s probe test surface facing the rotating arc of the magnet.When the wheel or the axis rotating,