| 摘要 |
PROBLEM TO BE SOLVED: To perform self-compensation of a zero point against a disturbance; to detect a magnetic material concentration continuously in a maintenance-free state; and to discharge easily and surely a solid material such as the magnetic material deposited near a coil. SOLUTION: This device is provided with oscillation circuits 11, 12 equipped with coils 9, 10 wherein, when detecting a frequency by one oscillation circuit 11, 12 in the covered state by a rotator 7 so as not to be affected by a fluid 2, an oscillation frequency is detected by the other oscillation circuit 11, 12 in the uncovered state by the rotator 7 so as to be affected by the fluid; a superposing circuit 13 for determining the frequency difference between each frequency detected by both oscillation circuits 11, 12; an F/V converter 14 for determining the peak difference of the frequency difference from the frequency difference of the preceding time and the frequency difference of this time from the superposing circuit 13; and a signal processing circuit 15 for determining the magnetic material concentration from the peak difference determined by the F/V converter 14. COPYRIGHT: (C)2007,JPO&INPIT
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