| 摘要 |
An adjustable magnetic field for nuclear magnetic resonance diagnostic devices is provided by a set of extending ferromagnetic bars mounted in one of a pair of opposing magnetic pole members. A second set of extending ferromagnetic bars may be mounted in the other magnetic pole opposite the first set of bars. Adjustment of the magnetic field may be achieved either by moving the ferromagnetic bars or by controlling current flow through coils placed about at least some of the ferromagnetic bars. In order to detect the actual field strength and configuration to provide for the requisite control signals, an array of Hall effect detectors is employed.
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