Name: Kongsberg MRU-E-JB3 Motion Reference Unit with JB3 Marine Junction Box, 6-DOF Attitude & Heave Sensor - MASSIVE
Brand: KONGSBERG

Description

Kongsberg MRU-E-JB3 Motion Reference Unit with JB3 Marine Junction Box, 6-DOF Attitude & Heave Sensor

Product Description

The MRU-E-JB3 is a complete fifth-generation Kongsberg Seatex marine motion sensing assembly consisting of the MRU-E inertial sensor head paired with the dedicated JB3 junction box. It integrates 3-axis MEMS gyros and accelerometers to measure roll, pitch, heave, angular rates and linear accelerations. The JB3 junction box provides AC input power conversion, terminal wiring, signal distribution, galvanic separation and expanded I/O interfaces, supporting Ethernet, dual RS232/RS422 serial ports and optional analog outputs. It runs the patented PFreeHeave algorithm, delivering both low-latency real-time heave and high-precision delayed heave for long wave periods. Widely used for DP vessel reference, multibeam hydrography, offshore crane compensation and USBL acoustic positioning. This package is widely deployed for retrofit of legacy Kongsberg marine motion systems.

MRU-E-JB3

Technical Parameters

Item	Specification
Manufacturer	Kongsberg Seatex, Norway
Model	MRU-E-JB3 (MRU-E sensor + JB3 junction box)
Measurement	6-DOF: Roll, Pitch, Heave, Surge, Sway, Angular Rates
Static Roll/Pitch Accuracy	0.03° RMS
Dynamic Roll/Pitch Accuracy	0.01° (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
Max Data Output Rate	200 Hz
JB3 Power Input	100–240 VAC, 50/60 Hz, 0.6 A
JB3 DC Output to Sensor	24 VDC, 0.63 A
Communication Interfaces	10/100 Mbps Ethernet UDP/TCP; 2× configurable RS232/RS422; analog 0–10 V / 4–20 mA via terminal block
Protocols	NMEA 0183, Kongsberg proprietary motion sentences
Sensor Enclosure	IP67, anodized aluminium
JB3 Junction Box	IP66 aluminium enclosure
Operating Temperature	-25 ℃ ~ +70 ℃
Certifications	DNV, ABS, BV, CCS, LR marine type approval, CE
Total Assembly Weight	Approx. 2.0 kg
Timing Synchronization	<1 ms

Recommended Related Models (8 units)

MRU-5: High-performance standalone fifth-gen MRU without separate JB junction box
MRU-E-JB1: Older generation MRU-E with JB1 junction box, limited serial-only I/O
MRU-H: High stability heave optimized variant for deep-sea survey
miniMRU: Compact lightweight MRU for ROV/AUV small payloads
DPS112: Kongsberg DGNSS position sensor, commonly paired for DP redundant reference
Seapath 320: Integrated GNSS heading & attitude system with embedded MRU core
MRU-E-CS8: Specified interconnection cable set between MRU-E head and JB3
K-Pos DP Controller: Native Kongsberg dynamic positioning host system

Compatibility & Installation Traps

Compatibility

Native host integration: Kongsberg K-Pos DP, multibeam echosounders, USBL acoustic positioning, hydrographic survey software
Configuration software: Kongsberg MRU PC Tools / K-Config
Timing sync: Compatible with GNSS PPS pulse for time-aligned survey datasets
Backward note: MRU-E sensor can run on older JB1 box, but analog outputs and second serial port will be unavailable

Critical Installation Traps

Separate Sensor & Junction Box: MRU-E-JB3 is a two-part system. The IP67 sensor head is mounted outboard/deck; JB3 must be fitted inside protected cabinet space, not exposed to direct seawater splash.
AC Power Input Miswiring: JB3 accepts 100–240 VAC mains; feeding raw vessel 24 VDC directly to the AC terminals will destroy the internal XP ECL15US24-E power supply.
Cable Compatibility Restriction: Older CS4 subsea cables cannot support Ethernet; use MRU-E-CS8 / CS10 cables when high-speed Ethernet output is required.
Lever Arm Offset Error: Motion is measured at the MRU-E sensor location. Failing to input accurate 3D lever-arm offsets to sonar or crane reference points creates large heave compensation bias.
Ground Loop Risk on Serial Lines: Vessel potential differences easily corrupt RS422 NMEA signals. Install galvanic isolators on serial lines between JB3 and remote acquisition units.
Heave Mode Misselection: Real-time heave has low latency but higher noise for long waves; delayed heave delivers superior precision with fixed latency, select per operational workflow.
Rigid Mount Mandatory: Sensor head must fasten to stiff vessel structure. Thin flexible panels amplify vibration and induce high attitude noise.
Axis Orientation Calibration: Incorrect definition of vessel fore-aft / port-starboard axis swaps roll and pitch data; verify axis mapping after mechanical installation.

Standard Operating Procedure (SOP)

Pre-installation inspection: Inspect MRU-E sensor housing, connector glands and JB3 enclosure for corrosion. Verify internal power supply part marking and firmware compatibility with host DP/survey software.
Mechanical mounting: Secure MRU-E sensor head on rigid deck structure with stainless fasteners. Mount JB3 junction box inside protected electrical cabinet, maintain clearance for ventilation. Record full lever-arm coordinates.
Cabling: Run approved CS8/CS10 interconnection cable between sensor and JB3. Separate signal wiring from heavy power cables; terminate all cable shields at the cabinet earth bar.
Power and terminal wiring: Terminate 100–240 VAC vessel supply to JB3 AC terminals. Wire Ethernet and serial outputs to host systems; fit surge protection.
Software configuration: Connect via MRU PC Tools, define vessel axis orientation, select output sentences, set update rate and choose real-time / delayed heave mode. Configure analog scaling if required.
Static and dynamic commissioning: Power up and validate roll/pitch/heave noise floor in stable conditions. Cross-compare motion data with independent attitude references during vessel sea trials.
Periodic maintenance: Quarterly visual inspection of glands, connectors and cable jackets. Annual static performance check. Re-calibration required after heavy shock or impact.
Decommissioning: Isolate AC mains supply before opening JB3. Disconnect sensor cable, cap all connectors, store sensor and junction box in dry shock-protected packaging.