Rotational speed detection device, rotational speed detection system, rotational speed calculation device and rotational speed detection method

Abstract

When calculating the rotational speed of a rotator, reference information is reduced. A rotational speed sensing device is provided, comprising: a magnet wire in which an alternating magnetic field with two or more cycles per revolution in an axial direction is provided, corresponding to a rotational operation of a rotator, wherein the magnet wire outputs a pulse with a polarity that depends on a change in one direction of the magnetic field; a magnetic polarity determination unit that determines, at a predetermined relative position with respect to the magnet wire, the polarity of a magnet forming the alternating magnetic field and contained in the rotator; and a computation unit that calculates a count value by counting a segment in a circumferential direction of the rotator, wherein the computation unit calculates the count value based on the polarity of the rotator's magnet that was last detected.calculated using a polarity of the pulse this time and a polarity of the rotator's magnet at the time the pulse this time is generated, and without using a polarity of the pulse from the last time.

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