FIELD: measurement.
SUBSTANCE: invention relates to measuring equipment and can be used in bucking a magnetic field of known geometry and time variation by means of a plurality of bucking loops. To this end, the invention utilises multiple loops, each of which is energised by an electric current that creates a magnetic field of known time variation. Multi-loop field forms a bucking magnetic field that better opposes the spatial variation in the known magnetic field over a volume than can the magnetic field from a single loop. Plurality of separate, substantially planar bucking loops, each being dimensionally smaller than the transmitter loop, arranged coaxially along an axis parallel to the local direction of said primary magnetic field and energised with current by a current controller; a nulling axis extends bi-directionally in a perpendicular direction from a plane parallel to said bucking loops to a termination point at each end of said nulling axis; a bucking magnetic field is formed within a bucked volume by current in said bucking loops, said bucked volume being substantially centered on said nulling axis, said termination points are located where the bucking magnetic field fails to substantially annul said primary magnetic field. Said bucking magnetic field is substantially in a direction opposite to, and is substantially equal in magnitude with, said primary magnetic field, such that said bucking magnetic field substantially annuls said primary magnetic field within said bucked volume. Invention is useful in electromagnetic measurements, where the magnetic field of a controlled source transmitter must be annulled at a magnetic field sensor. Invention is particularly useful for cases where the magnetic sensor may move relative to the transmitter, such as in certain airborne electromagnetic measurements.
EFFECT: technical result is expansion of functional capabilities.
19 cl, 16 dwg
