Setting up the input from a motion reference unit (MRU)
The information from a motion reference unit (MRU) (normally heave, roll and pitch information) is imported into the SN90 system to increase the accuracy of the echo data. The current roll and pitch values are shown on the top bar if you have enabled this in the Display Options dialog box.
Prerequisites
This procedure assumes that:
•  You have a vacant interface port on your Processor Unit.
•  You are familiar with NMEA and other relevant datagram formats.
•  You know how to set up the parameters for serial and local area network (LAN) communication.
•  The interface port is set up with the correct communication parameters.
•  The SN90 system is turned on and operates normally.
•  The new sensor is physically connected to the SN90 system using a serial or network cable. The sensor is turned on and in normal operation.
Neither tools nor instruments are required.
Context
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 SN90 system to stabilize the beams.
A hull unit may be provided as an option. It allows you to lower and hoist the transducer. A motion sensor for electronic stabilization of the sonar beams is provided. It is placed inside the Motor Control Unit. For improved operational accuracy, an external motion reference unit (MRU) can be used.
With hull unit
The SN90 system uses the built-in motion sensor. The sensor uses a local area network (LAN) port on your computer. A message on the page verifies that it is connected to the SN90 system’s beamformer application.
If you wish to use an external motion sensor, connect it to a vacant serial port, and set Port to the corresponding COM port.
Without hull unit
Use an external motion sensor connected to a local area network (LAN) or serial port on your computer.
Procedure
1 Connect the motion sensor system to an available communication port on your computer.
This is described in the Installation Manual.
2 Open the Setup menu.
3 On the Setup menu, select Installation.
Image
Observe that the Installation dialog box opens. This dialog box contains a number of pages selected from the menu on the left side.
Note
If you want to use a serial line to interface the motion sensor, and no COM ports are available, you must first release a port on the I/O Setup page. If you choose a serial COM port to interface the motion sensor, make sure that you do not put the same COM port to other use on the I/O Setup page.
4 Release an unused serial port (COM) port.
a On the left side of the Installation dialog box, select I/O Setup.
b Observe that the available serial interface ports on the Processor Unit are listed.
c If you have a vacant COM port, select it, then select Remove to delete it from the list.
d At the bottom of the page, select Apply to save your settings.
e Close the Installation dialog box.
f Restart the SN90 system.
A restart allows the Processor Unit to make the communication port available for other use.
g When the SN90 system has started, proceed to the Motion Reference Unit page to put the communication port to use.
5 On the left side of the Installation dialog box, select Motion Reference Unit.
6 Set up the interface.
If you select to use the LAN port, the SN90 system will automatically use the built-in motion sensor. Select COMx to connect to the external motion sensor. "COMx" is the serial port to which the motion sensor is connected. Select None to disconnect the SN90 system from both external and internal motion sensors.
a Select the Ethernet port or serial port you want to use.
b Select which protocol (datagram sentence) you want to use.
c If you are using a serial line, define the baud rate.
7 At the bottom of the dialog box, select Apply to save your settings.
8 Continue your work in the Installation dialog box, or select OK to close it.
Further requirements
If you choose a serial COM port to interface the motion sensor, make sure that you do not put the same COM port to other use on the I/O Setup page.
Note
To align an external motion sensor to the internal sensor, you may need to adjust the stabilization offset values.