OceanServer OS5000-S, Руководство пользователя

Страница: 17 / 30

17
4) Mount all compasses component side up (side 1 with arrow), level or true to
platform level with the arrow pointing forward. This is also the case when
using the USB connector on the OS5000-US.
5) Mount the compass in a mechanically stable location so this it moves with the
vehicle or device but doesn’t vibrate.
6) Metals such as aluminum, brass or copper do not block magnetic fields but
currents can still flow through them that could create unwanted local magnetic
fields. Metals such as iron and steel will distort the magnetic field.
OceanServer ships compasses with plastic standoff but users should insure that
the compass has sufficient distance from ferrous objects that could bend the
earth’s magnetic field and disrupt compass accuracy.
Aircraft Note : Most all electronic compasses use gravity to detect level and tilt with
accelerometers to measure tilt (including OceanServer compasses). The tilt angles are
determined by measuring the earth’s static gravitational vector. Since, dynamic and
static acceleration are indistinguishable when used in aircrafts with high acceleration
and banking turns, the dynamic acceleration will introduce an error in both roll and
pitch angle reported by the compass as well as heading errors. Only level headings will
be accurate when aboard a plane and vibration needs to be considered. Strong
vibration also applies acceleration to the compass and can cause errors if the amplitude
of the acceleration is significant as compared to the earth’s 1G acceleration due to
gravity
Mounting Location Example:
In one real world example if the compass is mounted 2 inches from a paddle wheel
the compass will see up to 90 degrees of offset in heading due to the magnets moving!
Since the magnetic field falls off as the inverse square of the distance moving the
compass a small distance can make large improvements in the accuracy.
Mounting Distance (inches) Error (heading degrees)
-------------------------------- ------------------------------
2” 90 degrees
5” 10 degrees
9” 1.6 degrees
11” 0.2 degrees