Geometrics G-822A, Руководство по эксплуатации

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Geometrics, Inc. G-822/G-823 Magnetometer Manual
5
4.1 Sensor orientation
Magnetic fields are vector fields. At any point they are defined by their magnitude and
direction. If the G-822A sensor is going to accurately measure the local magnetic field
magnitude, it must be properly oriented relative to the local magnetic field direction.
The sensor head must be oriented so that the local field impinges at an angle of from 30º
to 60º to the cylindrical axis of the sensor, for all platform attitudes. Alignments that
produce a field/axis angle less than 15º place the magnetic field within the sensor’s
"polar dead zone". Similarly, alignments that produce a field/axis angle greater than 75º
place the magnetic field within the sensor’s "equatorial dead zone". The sensor will not
produce usable data when the angle between the earth's field and the cylindrical axis falls
within one of these two zones.
Unless the sensor is quite near very magnetic objects, the local magnetic field will be
almost entirely due to the earth’s magnetic field. So, in latitudes where the inclination of
the earth's field vector is 45º, vertical orientation of the sensor’s axis will allow operation
in all practical flight attitudes. In equatorial regions it may be necessary to orient the
Figure 5
. Magnetic field intensity at the Earth’s surface.
Epoch 2000, 1000 nT contour interval.