February 2020 – TD 266 OPERATING MANUAL – ZPulse® DCS 4420/4830/4520/4930 Page 105
8.2 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 DCS has to be known. This is not possible with SeaGuard.
8.2.1 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 Figure 8-2. Moving transducer
1 clockwise gives an increasing heading.
• Find direction of magnetic north.
• Find x-axis on DCS, 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 DCS. Set the heading alignment offset equal to this
measured angle (input parameter heading see chapter 3.12.2. Also remember to select the external compass
as heading input to the DCS. Only available I AiCaP mode with SeaGuardII or SmartGuard
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 DCS is orientated upside-down.
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