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In the well-known world class range of motion reference units from Kongsberg Seatex, MRU Z is the ideal sensor for applications requiring heave compensation.
Typical applications
Typical applications for the MRU Z model are real-time heave compensation of echo sounders and offshore cranes. The unit provides heave measurements to meet IHO standards.
Function
The cost-effective MRU Z model is specially designed for use in marine applications and is the ideal sensor for heave compensation of echo sounders. The unit incorporates 3-axis Micro-Electro-Mechanical-Structures (MEMS) sensors for both linear acceleration and angular rate. This unit achieves high reliability by using solid state sensors with no rotational or mechanical wear-out
parts.
The unit is delivered with a Windows based configuration and data presentation software. By configuring the unit with the vector between the MRU and the measurement point (MP), the MRU Z will output accurate heave measurements in this point instead of where the MRU is mounted. Typical measurement point is the transducer head.
Each MRU Z unit is delivered with a Calibration Certificate stating that the unit is tested and found to be within the specifications. This unit has to be mounted in a fixed mounting direction with the connector pointing down.
Output variables
The MRU Z outputs heave position and velocity. Other outputs in addition are roll and pitch angels and corresponding angular rate vectors.
External inputs
The MRU Z accepts input of external speed and heading information to compensate for drift in the measurements due to turning. In addition an external one second time pulse signal can be input to the unit for complete synchronisation
of the MRU data with an external clock system (typical from a GPS system or other highly accurate time source).
Digital I/O protocols
For two way communication with the unit a proprietary binary serial protocol is used. Output variables are transmitted as IEEE 32 bit floats (recommended) or as
scaled integers. In addition, ASCII-based NMEA 0183 proprietary sentences or different Echo Sounder formats can be selected as data output protocols.
Technical specifications

Roll and pitch output
 Angular orientation range 45°
Angular rate range ±100°/s
Resolution roll, pitch 0.001°
Angular rate noise 0.1°/s RMS
Static** accuracy 0.1° RMS
Dynamic* accuracy (for a ±5° amplitude) 0.15° RMS
Scale factor error 0.4% RMS

Heave output
Output range 50m, adjustable
Periods 0 to 25 s
Dynamic accuracy (RMS) 5 cm or 5% whichever is highest

Acceleration output
Acceleration range ±40m/s2
Acceleration noise** 0.01 m/s2 RMS

Electrical
Power requirements 12-30V DC, Max. 3 W
Analog channels #4, ±10V, 14 bit resolution
Digital output variables #16 (max) RS232 or RS422
Output data rate (max) 100Hz (10 ms)
Internal update rate 400 Hz (angular)
　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　

　
　
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