Name: Kongsberg MRU-5 High Precision Marine Motion Reference Unit, Roll Pitch Heave Inertial Sensor - MASSIVE
Brand: KONGSBERG

Description

Kongsberg MRU-5 High Precision Marine Motion Reference Unit, Roll Pitch Heave Inertial Sensor

Product Description

The MRU-5 is a fifth-generation marine-grade motion reference unit developed by Kongsberg Seatex. It integrates three high-performance MEMS gyros and three precision accelerometers, delivering high-bandwidth measurement of roll, pitch, heave, angular rate and linear acceleration. Equipped with patented PFreeHeave algorithm, it provides stable real-time and delayed heave compensation for long wave periods. The unit supports dual-point lever-arm compensation, complies with IHO Special Order standards, and outputs motion data via Ethernet and serial interfaces. Widely used as a critical motion sensor for dynamic positioning, multibeam hydrographic survey, offshore crane compensation and underwater acoustic positioning. Each unit is factory-calibrated with an individual calibration certificate.

MRU-5

Technical Parameters

Item	Specification
Manufacturer	Kongsberg Seatex
Model	MRU-5
Sensor Type	3-axis MEMS gyroscope + 3-axis accelerometer
Static Roll/Pitch Accuracy	0.02° RMS
Dynamic Roll/Pitch Accuracy	0.005° (1-sigma)
Real-Time Heave Accuracy	5 cm or 5% RMS, up to 25 s wave period
Delayed Heave Accuracy	1 cm or 1% RMS, up to 50 s wave period
Data Output Rate	Up to 200 Hz
Power Supply	10–36 VDC, typical 24 VDC marine supply
Power Consumption	Max 8 W, typical 7.2 W
Communication Interfaces	10/100 Mbps Ethernet UDP/IP, RS422, RS232
Protocol	NMEA 0183, proprietary Kongsberg motion sentences
Mounting	Arbitrary orientation, M5 mounting holes
Operating Temperature	-5 ℃ ~ +55 ℃
Ingress Rating	IP67 sealed housing
Certifications	IHO Special Order, DNV marine approval, CE
Weight	Approx. 1.0 kg
Timing Precision	<1 ms synchronization

Recommended Related Models (8 units)

MRU-5+: Higher precision upgraded version, static roll/pitch 0.008° RMS
MRU-E: Cost-effective fifth-gen MRU for standard survey and vessel monitoring
MRU-H: High-stability variant optimized for heave-critical offshore operations
MRU-3: Mid-range motion reference unit for general DP and sonar systems
MRU-D: Compact roll/pitch sensor for vessel voyage recording and antenna stabilization
miniMRU: Small lightweight MRU for ROV, AUV and compact marine payloads
DPS112: Kongsberg DGNSS position reference sensor, paired with MRU-5 for DP
Seapath 320: Integrated GNSS attitude & heading system with embedded MRU-5

Compatibility & Installation Traps

Compatibility

Native integration: Kongsberg K-Pos DP systems, multibeam echosounders, hydrographic survey software, offshore crane motion compensation controllers
Supporting software: Kongsberg MRU PC Tools / K-Config for parameter setup and calibration
Synchronization: Compatible with GNSS PPS timing signal for time-aligned survey data
Signal consumers: Acoustic positioning systems, ECDIS, data loggers and third-party marine automation

Critical Installation Traps

Rigid Mounting Requirement: Mount only on solid, stiff vessel structure. Thin flexible panels or resonant structures amplify vibration and introduce noisy attitude readings.
Lever Arm Calculation Error: The MRU measures motion at its own mounting point. Failing to input accurate lever-arm offsets for survey transducers or crane reference points causes large heave and attitude compensation errors.
Magnetic & EMI Interference: Keep clear of high-current power cables, transformers, winch motors and magnetic compasses. Strong magnetic disturbance degrades inertial bias stability.
Temperature Exposure: Do not install near engine exhaust, boilers or direct deck sunlight. Sustained temperature above +55 °C leads to thermal drift and calibration shift.
Cable Ground Loops: Isolate serial RS422/RS232 lines between MRU and remote acquisition units. Vessel ground potential differences create noise and intermittent data dropout.
Heave Mode Misselection: Real-time heave has higher noise for long-period waves; delayed heave delivers better precision but introduces latency. Select mode matching the application.
Axis Alignment Marking: Incorrect definition of vessel fore-aft/port-starboard axes results in swapped roll and pitch signals. Verify axis orientation in software after mechanical installation.
Calibration Validity: Factory calibration is valid under specified environmental limits. Heavy shock or impact requires re-calibration before operational use.

Standard Operating Procedure (SOP)

Pre-installation inspection: Check housing, connector and cable gland integrity. Review factory calibration certificate and confirm firmware revision compatible with host system software.
Mechanical mounting: Fix with 4 off M5 stainless steel bolts onto rigid vessel structure. Record exact 3D lever-arm offsets from MRU to user reference points.
Cabling and grounding: Route power and signal cables separately from high-power cabling. Apply proper shielding termination and galvanic isolation for serial interfaces.
Software configuration: Connect via MRU PC Tools; define vessel axis orientation, select output sentences, set data rate and heave mode (real-time / delayed). Configure dual lever-arm compensation parameters.
Static bench test: Power up and monitor roll, pitch and heave readings in stable condition. Confirm noise level matches datasheet specification.
Sea trial commissioning: Compare MRU motion data with independent attitude references; perform static and dynamic cross-check during vessel maneuvers. Validate heave compensation on survey sensors or crane systems.
Periodic maintenance: Visual inspection of connectors and cable glands quarterly. Conduct static performance check annually. Re-calibrate after heavy impact or long-term high-vibration service.
Decommissioning: Disconnect 24 VDC power before removal. Cap connectors, store spare MRU in dry, shock-protected packaging.