KONGSBERG Seatex MRU 5 practical combat

Regular calibration: Although a calibration certificate is provided at the factory, it is recommended to retest the zero bias and scale factor every two years. It can be automatically completed in calm sea conditions through the "Static Calibration" function of MRC software.

Practical integration with mainstream devices

6.1 Connection with multibeam depth sonar (taking Simrad EM series as an example)

Connect the COM1 (RS-422) of MRU 5 to the motion sensor input port of the sonar processing unit.

Set the output protocol in MRC to "Simrad EM 1000" (or EM 3000/EM 2040 corresponding item), and set the output rate to 100Hz.

On the motion sensor configuration page of sonar software (such as SIS), select the "Seatex MRU" protocol and set the same baud rate as MRU 5.

Test: Start sonar acquisition and observe whether the real-time roll/heave curve is consistent with the actual motion of the ship. If the data jumps, check the shielding grounding.

6.2 Integration with DP system

DP systems such as Kongsberg K-Pos and Siemens typically require raw acceleration and angular velocity data. Recommended configuration:

Output format: Binary (including Ax, Ay, Az, RollRate, PitchRate, YawRate, Roll, Pitch, Heading)

Output rate: 20Hz (DP filter is sufficient, higher will waste CPU)

Communication protocol: Transfer to a serial server via serial port or Ethernet, and forward to a DP controller using UDP.

The compensation value of the lever arm must be rechecked in the DP system to prevent duplication with the compensation in MRU 5.

6.3 Data Extraction of Helicopter Deck Monitoring System

The system requires real-time heave and sway angles, and triggers alarms. NMEA 0183 proprietary statements can be used for output, such as:

PSHEV, 0.52, M, 0.03, D, 1.20, R * 4C (analysis: heave 0.52 meters, rise; Roll 0.03 degrees; Pitch 1.20 degrees)

Send this statement to the alarm unit on the deck and set a threshold (such as alarm when heave>3m or roll>2 °).

Common troubleshooting and diagnosis

7.1 Fault 1: MRU 5 has no output after power on (no data on serial port)

Phenomenon: The power LED is on, but the data receiving software does not display any characters.

Possible reasons:

Serial port line sequence incorrect (TX/RX crossover)

Baud rate mismatch

The output protocol was accidentally set to 'Polling mode' and requires an external trigger to output

Solution steps:

Measure the ground voltage of TX pin through oscilloscope or voltmeter: the idle state should be -5V~-12V (RS-232). If it is 0V, the port is damaged.

Try the "Auto detect" function using MRC software, which can automatically scan baud rates and protocols and reconstruct communication.

Enter the "Output Configuration" page of MRC and confirm that "Output Mode" is not "Polling". If real-time continuous output is required, select 'Continuous'.

Check if binary output is enabled, but the receiving end parses it in ASCII format - the two cannot recognize each other.

7.2 Fault 2: Periodic drift of lift and sink values, even with slow changes when stationary

Phenomenon: The ship is anchored at the dock, and the MRU 5 output heave value increases linearly or fluctuates sinusoidally with time.

Possible reasons:

External speed input is not connected, and the ship experiences slow drift due to slow water flow.

Vertical acceleration zero drift (possibly caused by temperature changes).

The compensation value input for the lever arm is incorrect.

Solution steps:

Temporary access to GPS speed (even if the speed is 0, zero speed reference can be provided). Observe whether the heave is stable. If stable, the problem is that there is no speed assistance.

Perform zero speed calibration: Select "Sensor Health" ->"Zero Calibration" in MRC, follow the prompts to place the sensor on a stationary horizontal plane, and automatically correct the acceleration zero point.

Recheck the value of the lever arm dz: If the symbol is reversed, it will lead to the accumulation of heave errors as the ship sways.

7.3 Fault 3: The dynamic accuracy of roll/pitch is significantly lower than 0.03 °

Phenomenon: Under known regular wave conditions (such as a wave simulation platform), the difference between the output of MRU 5 and the reference attitude gauge exceeds 0.1 °.

Possible reasons:

The installation base of the sensor is not level, and there is a fixed installation angle error.

The missing or incorrect bow input leads to the failure of attitude calculation under coupled motion.

Solution steps:

Check the installation surface with a high-precision digital level. If the offset is 0.2 °, the input offset angle can be corrected through MRC's "Mounting Alignment" without the need for physical reinstallation.

Ensure that MRU 5 receives reliable heading data (from either the gyrocompass or fiber optic compass). The NMEA statement should be HDT (True North) or HDM (Magnetic North), avoiding the use of HDG (including magnetic interference). Suggest inputting through COM3 with an update rate of at least 10Hz.

Check if there is a 'Heading Loss' warning in the' Internal Log 'in MRC.