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Robertson AP9 MK3 Autopilot
3.3
CD109 Course Detector
CD109 is the magnetic compass sensor in moulded plastic. It is
mounted to a vessel's magnetic compass to transfer the heading
information to the control unit. It operates on the fluxgate-principle
where the resultant of the compass magnetism and the magnetism
excited in the coil by the autopilot, makes it possible to register the
compass heading.
CD109 Course Detector Principle
The primary windings are excited by a pulsating signal. Dependent
of the magnetism induced by the position of the compass card
magnets (Heading), pulses of variable amplitude will be generated in
the secondary sine and cosine windings. These pulses are filtered
through the R/C network and amplified before entering the A/D
converter.
3.4
Course Handling
(Ref. Fig. 3-5).
The AP9 MK3 may use different combinations of heading sensors
such as magnetic compass (CD109), Gyrocompass (serial line,
synchro 1:1 and geared, step signal and fluxgate). The options are
selected by the compass select (COMP.SELECT) switch SW1 and
SW2 on the interface board.
One compass will thus provide steering signal (steering compass)
while the other will provide compass difference alarm (monitor
compass).
Course changes are made in three different ways:
1. By the course change knob when operating in AUTOPILOT mode
3-4
HEAD 2 (COS)
R1
C1
HEAD 1 (SIN)
R2
C2
Exitation
2.5V (Ref.)
Fig. 3-4
Course Detector principle
Digital Heading
A/D
CONV.
20169223D
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