| 摘要 |
A magnetic field cancelling system comprises a flux gate (12), bias coils (26, 28), flux sensing means (22) and a feedback means. The initial value of magnetic field as registered at the flux gate (12) by the flux sensing means (22) is maintained by measuring subsequent variations in magnetic field and using the feedback means to vary the current and produce a field fluctuation equal and opposite to subsequent fluctuations. The magnetic field cancelling system can be connected to a magnetic field production system to enable an area enclosed by the production system to be kept at a constant field value.
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