Chapter 4: Commissioning the Autopilot 8-4-11
ST290 Instrument System Owner’s Handbook
Step 1: Calibrating the compass
Note: This section does not apply if an NMEA compass is connected to
your autopilot system. In this case, refer to the information supplied with
the compass to determine the appropriate calibration routines.
Magnetic materials in the vicinity of the compass, can cause significant
compass errors. The compass calibration procedure (see Figure 4-7 )
reduces these errors to a few degrees, so you MUST perform this as the
first item in the seatrial.
Calibrationis achievedby turning yourboat in slow, wide circles, in calm
conditions and preferably on flat water (this is called ‘swinging the
compass’). For optimum calibration it is recommended that each turn of
the boat takes at least 2 minutes at a boat speed of under 2 knots.
If you fail to complete the deviation correction, autopilot
performance will be impaired.
Correcting for magnetic deviation
To correct for magnetic deviation, enter Seatrial Calibration, then:
1. Use the button to scroll to the SWING COMPASS page.
2. Use the or buttons to select ON.
3. Check that there is enough clear sea space to complete the maneuvers
required.
4. Press the button to begin the SWINGING COMPASS procedure.
5. Start turning your boat in slow, wide circles (typically 2 to 3 complete
turns will be needed):
• If the boat is turning too quickly, a TURN RATE TOO HIGH message
is displayed. Immediately reduce the rate of turn.
• If you have to stop the compass swing before completion, press
any button. If you do this, the message SWING ABORTED is dis-
played and the procedure will have to be restarted.
6. When the procedure is complete, the SWING COMPLETE screen is dis-
played, and the amount of deviation is shown.
Note: If the deviation figure exceeds 15° or the display shows no devia-
tion value, the compass is being affected by ferrous objects on your boat
and you should move the compass to a better location. Higher deviation
figures are acceptable on steel boats but you must verify the compass ac-
curacy with an independent reference.
7. Press the button to proceed to the ALIGN HEADING page.
81183_2 S8.book Page 11 Tuesday, May 6, 2003 9:08 AM
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