| 摘要 |
A highly sensitive magnetometer consisting of at least one pair of generally rectangular core elements having square hysteresis loops is disclosed. The primary windings of each of the cores are driven by an oscillator, with the secondary windings of each core being differentially connected through a null circuit, which serves to balance the effects of background fields, and a detector to a suitable indicator. The primary windings of the cores are operated in a resonance and the secondary windings are arranged to provide a high null output which eliminates the dead band caused by the threshold value of the diodes in the output detector circuit. This high null output may be accomplished by unbalancing the core windings or by feeding a portion of the primary winding drive current, or a signal synchronous therewith, to the corresponding secondary winding, thereby permitting measurement of the small magnetic fields which previously fell within the dead band of the device. Also disclosed is a method of aerial surveying and a guidance system for off-vertical drilling using the magnetometer.
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