Press up or down to change the stored variation value to the correct
value. Note that changing the magnetic variation has no effect on the
accuracy of the compass’s compensation (see page 7).
If it is desired to end Engineering adjustments, press ENTER to return to
normal heading indication, using the revised magnetic variation value.
MAGNETIC OR TRUE READOUT
If not already in Engineering (”En” displayed), hold down the ENTER button
while turning on the power to put the unit into Engineering mode.
Press ENTER and up together to switch between Magnetic and True
display of the compass readings. When True is selected “TRUE” is displayed,
and the variation shown is used to correct the readings made by the sensor.
When Magnetic is selected, “MAG.” is displayed as shown on Figure 6. In
Magnetic indication mode the variation value is ignored.
If it is desired to end Engineering adjustments, press ENTER to return to
normal heading indication.
13
COMPASS ERROR CORRECTIONS
In common with all magnetic compasses, the presence of magnetic objects in
the vessel can distort the earth’s magnetic field nearby, and affect the accuracy
of the detection of magnetic North, and the accuracy of readings at other
points of the compass. The errors are known as compass deviations. However,
compensation at these other points of the compass is seldom necessary if a
good position for the sensor head has been chosen which has no field
distortion by external magnetic objects.
Note that it is not necessary to do all the settings in sequence as described. If
the error at a particular angle is known to be negligible, there is no need to
align the vessel and log the compensation at that position. Additional
corrections can be added at different visits if a convenient alignment is
achieved.
HEADING ADJUSTMENT
It is important that the sensor is aligned with the vessel and reads North (0°)
when the vessel is pointing North. This should be verified before doing any
error corrections as described later. If the display does not correctly show the
0° heading, the sensor unit must be rotated slightly to bring it into alignment.
Slacken the sensor unit’s mounting screws sufficiently to allow the unit to be
turned, and rotate it until the display shows the known heading. Then re-tighten
the sensor unit’s mounting screws to lock the compass calibration at that
position
