PURPOSE: To make it possible to use a pickup even under the environment where iron powder and the like are present in a large quantity, by forming an iron core, so that it can be moved by the force of a spring, based on intermittent excitation of a coil.

CONSTITUTION: A magnetic path for detection is constituted by a permanent magnet 1, an iron core 2, a gear 3 which is an object to be detected, and a yoke 4. A coil 5 is interlinked with the magnetic path and induces a signal voltage by the change in magnetic flux generated by the rotation of the gear 3 that is the object to be detected. The coil 5 is provided so that it acts as an electromagnet for an intermittent current from the outside. The iron core 2 is formed so that it can be moved by the force of a spring based on the intermittent excitation of the coil 5. In this constitution, since iron powder and the like, which are attached and bridged between the iron core 2 and the yoke 4 in the vicinity thereof, are made to fall, the pickup can be used under the environment where the iron powder and the like are present in a large quantity.