JRC JLN-740 Speed Log


The JRC JLN-550 speed log has been discontinued and replaced with the JRC JLN-740 speed log.

Please note that IMO regulation MSC.334(90), requires reading over water and over the ground.


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.

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. 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.

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 JRC JLN-740 Speed Log 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.


  • 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.

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