Abstract
A magnetism sensing apparatus comprising an application coil (1) for generating an AC magnetic field the frequency of which is variable; a power supply (2) used for the application coil; a magnetometric sensor measurement circuit (7) having a magnetometric sensor (5), which is operative to sense a change in magnetic field due to a subject (9) to be measured, disposed away from the plane of the application coil and close to the subject (9) and also having a cancellation coil (6), which is operative to cancel a DC magnetic field and/or a magnetic field generated at the magnetometric sensor (5) by the application coil (1), disposed at the magnetometric sensor (5), the magnetometric sensor measurement circuit (7) being operative to measure a detection signal from the magnetometric sensor (5); a lock-in amplifier circuit (8) that detects an output from the magnetometric sensor measurement circuit (7) as one of two signals having the same frequency as the application coil (1) and also having respective phases that are mutually different by 90 degrees; and analyzing means (10) that uses an output signal from the lock-in amplifier circuit (8) to analyze a phase change in the output of the magnetometric sensor (5).
| Original language | English |
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| Patent number | WO2006009048 |
| IPC | G01R 33/ 02 A I |
| Priority date | 7/16/04 |
| Publication status | Published - Jan 26 2006 |