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July 2019 – TD 304 OPERATING MANUAL – Doppler Current Profiler Sensor
CHAPTER 9
Other details
9.1
Compass heading 0° reference direction
In some cases it is necessary to know the orientation of the sensor’s axes. This can be necessary when the sensor is
placed in a fixed position with a fixed orientation (for example in a frame on the sea floor) where the magnetic influence
by an object nearby gives an erroneous heading measurement. In this case the fixed heading input can be enabled, but
to set the correct fixed heading the 0° reference has to be known. On surface buoys made of iron/steel there can also
be problems related to magnetic influence from the buoy structure/body. This can be improved by using an external
compass (parameter input via SeaGuardII or SmartGuard Datalogger) placed away on a mast arm which gives a more
correct compass heading to the sensor. In this case the misalignment/offset between the external compass and the
axes on the DCPS has to be known.
9.1.1
Transducer 1 is 0° reference
When transducer 1 on the sensor is orientated towards magnetic North, the compass heading is 0°. One method is to
measure in which direction transducer 1 is pointing. Position of transducer 1 is shown in
. Moving transducer
1 clockwise gives an increasing heading
.
•
Find direction of magnetic north.
•
Find x-axis on DCPS, axis with transducer 1 and 3
(opposite side on same axis).
•
If a fixed and non-moving application, align x-axis
and transducer 1 towards correct magnetic north.
Alternatively measure the angle clockwise from
magnetic north to x-axis transducer 1 and set the
fixed heading equal to this value (degrees).
•
If used on a buoy with external compass input, align
the x-axis transducer 1 in the same direction as the
north mark on the compass. Alternatively, try to
measure the clockwise angle from the north mark (0
degree) on the external compass to the x-axis
transducer1 on the DCPS. Set the heading
alignment offset equal to this measured angle (input
parameter heading see
chapter 3.5.9
. Also
remember to select the external compass as
heading input to the DCPS.
Figure 9-1 Orientation transducer 1
NOTE: To check the value measured by the tilt and heading sensor refer to chapter 4.2. Viewing incoming data
in real-time.
The same procedure can be used if the DCPS is orientated upside-down.