Adjusting the built-in motion sensor offset
The information from a motion reference unit (MRU) (normally heave, roll and pitch information) is imported into the SY50 system to increase the accuracy of the echo data. The SY50 system is provided with a built-in motion sensor to provide electronic stabilization of the sonar beams. It is located inside the Power Supply Unit.
Prerequisites
The SY50 system has been set up with its hardware units connected as specified in the Installation Manual.
•  The SY50 system is turned on and operates normally.
•  The SY50 system is in Normal mode, but TX Power is set to Off to prevent transmissions.
•  The vessel is berthed or at sea.
•  Neither tools nor instruments are required.
Context
The Power Supply Unit is mounted on the bulkhead close to the hull unit. The purpose of the Power Supply Unit is to provide the hull unit with the necessary power for operation. The Power Supply Unit further contains the logic circuitry required to control the lower and hoist operation, as well as a small motion sensor.
If the Power Supply Unit has been mounted with its door pointing straight aft, you do not need to enter any rotation values. If the unit faces in any other direction you must compensate for this by typing the relevant value for Rotation Around Z.
Independent of the power supply orientation, the offset of the built-in motion sensor is always defined as:
The angle measured from the bow to the motion sensor’s 0° reference.
On the MRU page, define the offset as rotation around Z.
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Rotation Around Z:
A Unit facing aft: 0 degrees
B Unit facing port: +90 degrees
C Unit facing forward: ±180 degrees
D Unit facing starboard: -90 degrees
Note
Do not confuse stabilization offset with installation offset. The installation offset values describe the physical location and orientation of an item, and how this location is related to the vessel's coordinate system. The stabilization offset values describe any misalignments related to the measurements a sensor make.
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Illustration:
A Rotation around the x-axis: In the positive horizontal direction (forward), a positive rotation is clockwise.
B Rotation around the y-axis: In the positive horizontal direction (starboard), a positive rotation is clockwise.
C Rotation around the z-axis: In the positive vertical direction (down), a positive rotation is clockwise.
D Reference point (Ship Origin)
Procedure
1 Estimate the alignment angle from the bow (vessel’s centre line) to the 0° reference mark for the built-in motion sensor.
Do this as accurately as possible.
2 On the Setup menu, select Installation.
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Observe that the Installation dialog box opens. This dialog box contains a number of pages selected from the menu on the left side.
3 On the left side of the Installation dialog box, select the small white triangle next to Installation Parameters.
Observe that a menu opens with access to all the individual pages.
4 Select MRU to open the page.
5 Insert the alignment offset angle as a rotation around Z.
•  If the 0° reference mark for the built-in motion sensor points to the starboard (right) side of the vessel’s centre line (as shown in the illustration), insert the offset as a number between 0 and +180 degrees.
•  If the 0° reference mark points to the port (left) side of the vessel’s centre line, insert the offset as a number between 0 and –180 degrees.
6 At the bottom of the page, select Apply to save your settings.
7 Continue your work in the Installation dialog box, or select OK to close it.