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Date: Mar 28, 2024Views:

  Typical applications

  The MRU H is specially designed for motion measurements in marine applications requiring highly accurate heave measurements in environments with extreme horizontal accelerations. This MRU is an ideal sensor for roll, pitch and heave compensation of offshore cranes and echo sounders. The MRU H can also be used for typical ship motion monitoring applications such as helideck motion monitoring, hydroacoustic positioning systems, as well as hull stress monitoring.



  The MRU H incorporates three highly accurate accelerometers and three Micro-Electro-MechanicalStructures (MEMS) angular rate gyros. This unit achieves high reliability by using solid state sensors with no rotational or mechanical wear-out parts.

  The unit is delivered with Windows based configuration and data presentation software. In this software vector arms from where the MRU is mounted to center of gravity (CG) and two individually configurable monitoring points (MPs), can be defined. The heave measurements can be output in four different locations (the MRU itself, CG, MP1 and MP2) simultaneously on serial lines or Ethernet port. Typical monitoring point is the transducer head or the crane tip.

  Output variables

  The MRU H outputs roll, pitch and heave together with linear acceleration in 3-axes. The MRU H outputs heave position, velocity and accelerations in adjustable frames. In addition roll and pitch angles and corresponding angular rate vectors are output.

  PFreeHeave® Algorithm

  The PFreeHeave algorithm uses past measurements to output a correct and phase-free heave from the MRU. PFreeHeave has an advantage in long swell conditions and for applications that can utilize a heave signal that is delayed some minutes, typical seabed mapping applications.

  External inputs

  The MRU H accepts input of external speed and heading information on separate serial lines or Ethernet for improved accuracy in heave, roll and pitch during turns and accelerations. For time synchronization the MRU accepts 1-second time pulse (1PPS) input on a TTL line (XIN) or as RS-232/422 signal.

  Digital I/O protocols

  For this fifth generation MRU data is available through both Ethernet interface and serial lines enabling easy distribution of MRU data to multiple users on board the vessel. Output protocols for commonly used survey equipment are available on two individually configurable serial lines and Ethernet/UDP.


  • High accuracy heave measurements even in dynamic environments

  • Outputs on RS-232, RS-422 and Ethernet

  • High output data rate (200 Hz)

  • Precise heave at long wave periods by use of PFreeHeave® algorithms

  • Lever arm compensation to two individually configurable monitoring points

  • Meets IHO special order requirements

  • Small size, light weight and low power consumption

  • No limitation to mounting orientation

  • Each MRU delivered with Calibration Certificate

  • Selectable communication protocols in the Windows based MRU configuration software

  • 2-year warranty


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