Abstract: A magnetic path is formed, in response to the rotation of a motor, by a magnetic detector (24 or 26) (more exactly, a magnetic wire (70)), a magnetic pole of the magnet (22), which is placed counter to each magnetic detector, and the rotating shaft (20). The magnetic wire (70) is formed of a magnetic material capable of causing a large Barkhausen jump. Whenever the magnetic pole opposite each magnetic element changes in response to the rotation of the motor, the direction of magnetic field constituting the magnetic path changes precipitously and a pulse signal in response to the change is outputted from the magnetic detector. Since the direction of magnetization of the magnetic wire (70) changes with a change in magnetic flux density received from a magnet (22), an induced electromotive force occurs due to a change in magnetic flux received by a detection coil. This makes enables the magnetic detector to output pulse signals without power supply.

Abstract: The rotation period of a motor is subdivided by edge interval times and a rate of change between a currently calculated edge interval time and an edge interval time calculated one rotation of the motor previously is calculated at the detection of each edge. Then the rotation period of the motor is calculated by multiplying a set reference period by the calculated rate of change.

Abstract: A magnetic path is formed, in response to the rotation of a motor, by a magnetic detector (24 or 26) (more exactly, a magnetic wire (70)), a magnetic pole of the magnet (22), which is placed counter to each magnetic detector, and the rotating shaft (20). The magnetic wire (70) is formed of a magnetic material capable of causing a large Barkhausen jump. Whenever the magnetic pole opposite each magnetic element changes in response to the rotation of the motor, the direction of magnetic field constituting the magnetic path changes precipitously and a pulse signal in response to the change is outputted from the magnetic detector. Since the direction of magnetization of the magnetic wire (70) changes with a change in magnetic flux density received from a magnet (22), an induced electromotive force occurs due to a change in magnetic flux received by a detection coil. This makes enables the magnetic detector to output pulse signals without power supply.

Abstract: The rotation period of a motor is subdivided by edge interval times and a rate of change between a currently calculated edge interval time and an edge interval time calculated one rotation of the motor previously is calculated at the detection of each edge. Then the rotation period of the motor is calculated by multiplying a set reference period by the calculated rate of change.