| 摘要 |
The present invention provides an apparatus and method for creating a magnetic cavity in a region about the centerpoint of two concentric, magnetic field-generating electrical wire coils. The outer of the two coils generates a strong primary magnetic field that may induce a relatively weak magnetic field in a remote conductive material, such as subterranean mineral deposits. The inner of the two coils generates a secondary magnetic field having a smaller amplitude and an opposite polarity from the primary field. Various parameters of the apparatus are calculated so that the two oppositely polarized magnetic fields mutually cancel each other in a specified region inward of the two coils about their centerpoint, creating the magnetic cavity. A magnetic sensor can then be isolated within the magnetic cavity for detecting the weak induced magnetic field in the remote conductive material without interference from the nearby primary and secondary magnetic fields.
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