Motion Reference Unit page
The motion reference unit (MRU) measures the roll and pitch movements of the vessel. Some sensor models also measure heave. The information provided by the motion sensor is used by the ST90 system to stabilize the beams.
Prerequisites
The Installation dialog box is not available when your ST90 system is set to Replay mode.
How to open
This page is located in the Installation dialog box. To open the page, select Installation on the Setup menu.
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Description
The ST90 system is provided with a built-in motion sensor to provide electronic stabilization of the sonar beams. It is placed inside the Motor Control Unit. For improved operational accuracy, an external motion reference unit (MRU) can be used.
Use the Motion Reference Unit page to define the data format and the communication port used to import motion information from an external sensor.
Note
The sensor must be connected with a serial communication line. If you don’t have any available COM ports you must first release one on the I/O Setup page. Make sure that you do not put the same COM port to other use on the I/O Setup page.
If you select to use the LAN port, the ST90 system will automatically use the built-in motion sensor.
Tip
If the sensor is malfunctioning the input can be disabled. The Stabilization function allows you to enable or disable the input from the motion sensor. This function is opened from the Setup menu.
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Details
Port
Select the serial port you want to use for communication. If you select to use the LAN port, the ST90 system will automatically use the built-in motion sensor.
LAN
If you select to use the LAN port, the ST90 system will automatically use the built-in motion sensor.
COM Port
Select COMx to connect to the external motion sensor. "COMx" is the serial port to which the motion sensor is connected.
None
Select None to disconnect the ST90 system from both external and internal motion sensors.
Protocol
Select which datagram formats to import. The ST90 system supports the following datagram format from a motion sensor:
•  ASCII
•  Kongsberg EM Attitude 1000
The EM Attitude 1000 is a proprietary datagram format created by Kongsberg Discovery for use with digital motion sensors. It holds roll, pitch, heave and heading information. In many new designs, this datagram format has been replaced with EM Attitude 3000 format.
•  Kongsberg EM Attitude 3000
The Kongsberg EM Attitude 3000 is a proprietary datagram format created by Kongsberg Discovery for use with digital motion sensors. It holds roll, pitch, heave and heading information.
Baud Rate
Use this setting to specify the baud rate ("speed") for the serial communication.
Status
The current status of the sensor communication is shown. "Not connected" means that the input from the sensor is missing. A message like this (example) verifies that the ST90 system is connected to the built-in motion sensor:
Connected to 192.168.1.30 ST90 Beamformer
Related functionality
Stabilization
The Stabilization function allows you to enable or disable the input from the motion sensor. If you disable the input from the sensor, the beams will not be compensated for pitch and roll movements. This function is opened from the Setup menu.