ROTATION SENSOR

PROBLEM TO BE SOLVED: To accurately detect a rotation angle of a second rotor corresponding to the rotation speed of a first rotor without being affected by a dimensional error and assembling tolerance based on cumulation of dimensional tolerances of a component and an influence of deformation of the component caused by a long-time use.SOLUTION: The rotation sensor includes: a first rotor 10 that is attached to a measuring object rotor 11 and rotates along with the rotation of the measuring object rotor; first detecting means 100 for detecting a rotation angle of the first rotor for every predetermined angle range; a second rotor 20 that is mechanically connected to the first rotor, rotates in conjunction with the first rotor, and rotates at a rotation speed lower than the rotation speed of the first rotor; and second detecting means 200 for detecting the second rotor for every predetermined angle range. When detecting the rotation speed of the first rotor, the rotation sensor determines whether an output value of the first detecting means is approximate to an initial value or a terminal value, and performs a predetermined correction process from the output value of the first detecting means to the output value of the second detecting means according to the determination result.