Page 108 February 2020 – TD 266 OPERATING MANUAL – ZPulse® DCS 4420/4830/4520/4930
8.4 Checking the compass
First point transducer 1 towards North. The compass heading should lie close to 360°/0° (same point).
NOTE: To check the value measured by the tilt and heading sensor refer to chapter 4.2. Viewing incoming data
in real-time.
A clockwise rotation gives an increasing compass angle. Keep the sensor away from magnetic object like table legs (if
iron, these are acting as a permanent magnet magnetized by the earth magnetic field). Big objects like for example a
car outside the room where the compass is tested can affect the earth magnetic field at the point where the sensor is
placed. Also the structure of the building can influence on the earth magnetic field around the sensor.
Be aware that nearby objects may influence the magnetic field when the sensor is used. This can for example be a
problem on a buoy as described above or if hanging from a boat. The rule of thumb is that the bigger the magnetic
object is (hard and/or soft magnetic) the further away sensor should be positioned to eliminate the influence. If the
sensor is in a fixed position the fixed heading input can be used as described earlier in this chapter. On buoys the
solution is often to use an external compass which is placed on a non-magnetic mast away from the buoy.
Even alkaline batteries can be a problem if placed close enough to the sensor. When used on SeaGuard or SeaGuardII
the upper battery compartment can give problems when using alkaline battery cells. The battery cells provided by
Aanderaa do not give problems when using the lower battery compartment. When batteries are own-built, you have to
be aware of this problem. The influence from the batteries can be checked by looking at the heading output from the
sensor while placing the batteries closer to the sensor. Moving the batteries around a hand held compass also gives a
good indication on whether the batteries are low magnetic or not. Batteries can also be degaussed to reduce the
magnetic influence from the batteries.
8.5 Checking the tilt sensor
The sensor has a 3-axis inclinometer. The tilt is converted to rotational angles pitch and roll. When the sensor is placed
horizontal the pitch and roll should be close to zero. Pitch is the rotation around the y-axis while roll is the rotation angle
around the x-axis. The x-axis is aligned with transducer 1 and 3 and the y-axis is aligned with transducer 2 and 4.
• Place the sensor horizontal. See that the pitch and roll is close to zero.
• Tilt sensor towards transducer 1 (transducer 1 downwards) and see that the pitch value is decreasing (more
negative).
• Tilt the sensor in the opposite direction against transducer 3 and see that the pitch is increasing (positive).
• Tilt the sensor towards transducer 2 and see that the roll value is increasing (positive).
• Tilt the sensor towards transducer 4 and see that the roll value is decreasing (more negative).
• Hold the sensor upside-down and horizontal. The roll should now be close to 180 degrees.
• Place the sensor upside-down on a table on transducer 1. The pitch should be close to -25 degrees and the roll
close to 180.
• Do the same now on transducer 3. The pitch should now be close to +25 degrees and the roll close to 180.
• Do the same now on transducer 2. The roll should be close to 155 degrees while the pitch should be close to 0.
• Do the same on transducer 4. The roll should be close to 205 degrees and the pitch close to 0. For software
version 8.2.1 and over, the roll range is ±180 so the roll reading should be close to -155.
NOTE: To check the value measured by the tilt and heading sensor refer to chapter 4.2. Viewing incoming data
in real-time.
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