| 摘要 |
PROBLEM TO BE SOLVED: To provide a magnetic shielding room which locates a loose arrester at a loosed portion of a canceling coil passing a door of the magnetic shielding room to prevent a generation of a new noise magnetic field, and when a strong magnetic field exceeding a predetermined value intrudes, records its intrusion state as a history or raises an alarm, thereby, can attain a maintenance of accurate measurement data. SOLUTION: The magnetic shielding room of internal active magnetically shielded system is equipped with a magnetic shielding room having a coil for canceling a magnetic field, a sensor S which is located in the magnetic shielding room and detects a magnetic field leaked from outside, a signal control portion which analyzes a composition of an intruded magnetic field, receiving a detected signal from the sensor S and computes a composition of a magnetic field to cancel the intruded magnetic field, a canceling current sending circuit which sends an exciting current to the canceling coil, receiving the signal from the signal control portion, and a level detection device which records its measured value and raises an alarm when the value measured by the sensor S exceeds the predetermined value. COPYRIGHT: (C)2008,JPO&INPIT
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