How do I choose the right motion sensor?
Choosing the right motion sensor ensures optimal performance and reliability for your specific needs. At Norwegian Subsea, we offer a range of high-performance Motion Reference Units (MRUs) designed for diverse marine, subsea, and offshore applications. The selection process primarily depends on the operational environment, required accuracy, connectivity needs, and specific functionality.
First, consider the installation environment. Our MRU Compact (IP65) is ideal for indoor or control box mounting, featuring easy plug-and-play installation with passive Power over Ethernet (PoE) via an RJ45 connector. For on-deck or shallow subsea applications (up to 50m), the MRU Marine (IP68) provides robust performance with versatile connectivity options including Ethernet, RS-232/485, and PPS. For deep-water applications up to 6000m, the MRU Subsea offers a compact, high-pressure titanium housing with Subconn connectors. If operating in hazardous areas, the MRU Ex provides a certified stainless steel solution (II 2 G Ex d IIC Gb).
Next, determine the required accuracy. All our MRU models are available in three accuracy tiers for Roll & Pitch: the 3000 series (±0.05°), the 6000 series (±0.02°), and the high-precision 9000 series (±0.01°). Heave accuracy is consistently high across models at 5.0 cm or 5.0%. All sensors utilize advanced sensor fusion algorithms and state-of-the-art MEMS technology, validated in real sea conditions.
Evaluate your system integration requirements. Norwegian Subsea MRUs support a wide range of standard and customizable data protocols (e.g., UDP, Modbus TCP, Ethernet/IP, NMEA, Modbus RTU) over Ethernet and serial lines (RS-232/485), ensuring seamless integration. We offer various connector options (RJ45, Marine 16-pin, Subconn, Pigtail) and flexible cable lengths. Our sensors are designed for easy configuration via a web browser interface, requiring no software downloads.
Finally, consider the required output data. While our standard MRUs provide full 6 Degrees of Freedom (6DoF) measurements (Roll, Pitch, Heave, Yaw, Surge, Sway), we also offer Inclinometer/VRU versions across all models. These provide the same high Roll & Pitch accuracy but without Heave, Surge, and Sway outputs, offering a cost-effective solution when only attitude data is needed. All Norwegian Subsea sensors can be mounted in any orientation and are known for their long-term stability, often eliminating the need for recalibration, making them ideal for both new installations and cost-effective retrofitting.
Related products
Usage area
IP 65
Connectors
RJ45 or RJ50
Roll & Pitch accuracy
- 3000±0.05°
- 6000±0.02°
- 9000±0.01°
Heave accuracy
5 cm or 5.0%
Usage area
50 m depth, IP 68
Connectors
Lemo or SubConn 8 or SubConn 16
Roll & Pitch accuracy
- 3000±0.05°
- 6000±0.02°
- 9000±0.01°
Heave accuracy
5 cm or 5.0%
Usage area
6000 m depth
Connectors
SubConn 8
Roll & Pitch accuracy
- 3000±0.05°
- 6000±0.02°
- 9000±0.01°
Heave accuracy
5 cm or 5.0%
Usage area
Hazardous areas
Connectors
Pigtail cable
Roll & Pitch accuracy
- 3000±0.05°
- 6000±0.02°
- 9000±0.01°
Heave accuracy
5 cm or 5.0%
Further reading
Advanced motion compensation for sonars introduced at Ocean Business 2025
MRUs for vessel performance optimisation in focus at Europort 2025
Research Project to Test Value of MRU Data for Vessel Performance and Carbon Reduction
Related questions
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What is the difference between the MRU Marine and MRU Marine SW?
- The MRU Marine has an IP-68 rating, uses a Lemo 16-pin connector and has indicator lights.
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When navigating the complexities of motion sensing and navigation systems, it is essential to understand the distinctions between devices and systems like Inertial Measurement Units (IMUs), Inclinometers, Roll & Pitch sensors, Vertical Reference Units (VRU), Attitude and Heading Reference Systems (AHRS), Motion Reference Units (MRUs), Gyrocompasses, and GNSS-Aided Inertial Navigation Systems (GNSS/INS). Each serves specific purposes and offers different levels of functionality, accuracy, and application scope.
Gyrocompass
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The MRU Compact uses a standard RJ45 ethernet cable where power is supplied through Passive PoE (Power over Ethernet). In most cases you cannot connect the MRU directly to a an ethernet switch with PoE, since most of these are Active PoE.
We normally supply your first MRU Compact with a start kit containing a POE RJ45 spliter socket. You will only need standard RJ45 cat5 ethernet cables to connect the MRU to the spliter socket and the spliter socket to your PC or ethernet switch.
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