MAGNETIC SUBSTANCE DETECTOR, IMAGE FORMING DEVICE OR DIGITAL COPYING MACHINE USING THE SAME, TONER DENSITY DETECTOR AND CONDUCTOR DETECTOR

摘要

PROBLEM TO BE SOLVED: To stably implement a magnetic substance detection operation in terms of toner density or the like and to improve the sensitivity of the magnetic substance detection.;SOLUTION: This magnetic substance detector is used for detecting the presence of a magnetic substance and a magnetic substance amount 26 by disposing the magnetic substance in a proximity region of a coil. The coil comprises a first coil L1 for a first resonant circuit and a second coil L2 for a second resonant circuit. A capacitor C3 for the first resonant circuit is used for a capacitor C3 for the second resonant circuit in common. The resonant frequency of the first resonant circuit is determined based on the first coil and the common capacitor, and that of the second resonant circuit is determined based on the second coil and the common capacitor. The resonant frequencies of the first and second resonant circuits are almost equivalently set. A detection circuit comprising the first and second resonant circuits uses the output from an oscillation circuit oscillating at a predetermined certain frequency as its input, and extracts and outputs phase difference between the input side V1 and the output side V2 thereof.;COPYRIGHT: (C)2002,JPO