ComNav Commander P2 & P2VS Installation & Operation System Overview
Document PN 29010074 V4.1 - 33 -
Magnetic Compass Sensor
PN 20320002
The ComNav Magnetic Compass Sensor detects the position of the compass card of an
externally gimballed magnetic compass. The sealed unit can be attached to the bottom of
any of ComNav’s Magnetic Compasses, or the bottom or top of many other brands of
externally gimballed magnetic compasses. It is wired directly to the SPU, with the attached
7.6 metre (25’) cable.
Figure 11 – Magnetic Compass Sensor
Magnetic Compasses
ComNav offers several high-quality externally gimballed Magnetic Compasses, of either
13 cm (5”) or 15 cm (6”) diameter, which are directly compatible with the ComNav Magnetic
Compass Sensor. These compasses are available in either bracket mount or binnacle
mount. Compensating spheres and arms are also available. Consult your ComNav Dealer
for part numbers.
Figure 12 – Externally Gimballed Magnetic Compass with Binnacle
The advantage of using a Magnetic Compass with a Magnetic Compass Sensor attached to it
is that the Autopilot is sensing the position of the magnets on the compass card rather than
sensing the earth’s magnetic field directly.
Since the card of the compass has physical inertia, it does not react immediately to the
changes in the magnetic field it is immersed in, but only to those changes which persist long
enough to overcome the resistance of the compass card to movement. This means that the
compass is a more stable heading reference than a Fluxgate Compass. The Magnetic
Compass will largely ignore changes in the magnetic field in the plane of the compass card
caused by boat motion, whereas a Fluxgate Compass may react to such changes.
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