Doppler Speed Log JLN-740 Series

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Image:Highly accurate speed and distance log for high-mileage trips.

Image:Speed Log JLN-740

Image: Speed Log JLN-740

Highly accurate speed and distance log for high-mileage trips.

  • IMO MSC.96(72)-compliant Doppler Speed Log; compatible with ships above 300 GT.
  • Measures ship speeds within a range of 0.03kn or 0.3%*with greatly improved ship speed
    tracking to assist with precise navigation during berthing.
  • Equipped with proprietary bubble detection, which informs when speed accuracy is
    reduced due to bubble contact.
  • Color LCD display model with touch panel for improved night visibility is also available.
  • Also available in a three-unit model, which provides smaller ships with the same
    exceptional speed tracking capability.


The JLN-740 series is a Doppler Speed Log compliant with the IMO MSC.96(72) standard, required on all internationally-voyaging ships exceeding 300 GT. Boasting never-before-seen accuracy for speed measurement, the JLN-740 is also installed with our company's proprietary bubble detection, which informs you when measurement accuracy is impaired due to air bubble contact. A model featuring color LCD touch panels for the main and sub displays, allowing you to view important information and adjust brightness in all displays from one location, is also available.

Precise Ship Speed Tracking

The JLN-740 series utilizes digital signal processing, which, coupled with optimizations to existing speed measurement waveforms and the reliability of ship bottom mounting, has resulted in water speed measurement with accuracy up to 0.03kn or 0.3% in all models*1. That accuracy of information allows for highly fuel-efficient speeds, which means faster voyages with less waste. Along with improved speed measurements, the series also has greatly improved ship speed tracking, relaying all the information you need for precise navigation during berthing.

  1. At fixed speeds (measured value).

Image:Speed measurement

Speed measurement image

Bubble Detection

A long-unsolvable problem with doppler-based water speed measuring systems was reduced accuracy from bubbles making contact with the measuring device on the bottom of the vessel. The JLN-740 series detects when bubbles contact the transducer, and - using proprietary technology from JRC - alerts you of reduced measuring accuracy via the display. Confirming the source of the issue typically requires visually examining the device on the bottom of the ship. However, onboard air bubble detection allows you to skip unnecessary preventive maintenance.

Image:Bubble Detection

BUBBLE DETECTED alert message

Performance Standard Compliant

The JLN-740 series is compliant with the IMO MSC.96(72), A.824 (19), and A.694(17) standards, required on all internationally-voyaging vessels exceeding 300 GT, and meets standards for the following IEC environmental test standards

IEC 60945(2002)
Marine speed and distance measuring equipment(SDME)
IEC 61023(2007)
Presentation of navigation-related information on shipborne navigational displays
IEC 62288(2014)
Digital interfaces - Single talker and multiple listeners
Digital interfaces - Ethernet interconnection

In addition, when used with JRC’s Satellite Log JLN-720, ships exceeding 50,000 GT can meet the requirements for IMO MSC.334(90).

  1. Only supports JLN-740A/N