Japan Radio Co. JLN-740A, Instruction Manual

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1-1 Chapter 1 Outline of the Equipment
1
Chapter 1 General
1.1 Functions
The JLN-740A/740N/741A/741N Doppler log is the equipment that accurately measures the speed
through the water and navigation distance of the ship by emitting ultrasonic signals to the fore and the
after in the water from the transducer that is installed in the bottom of the ship and using the Doppler
effects of the ultrasonic signals that are reflected from the underwater.
This equipment measures the relative speed through the water at 3m or more from the bottom of a ship.
Therefore, the equipment can measure the ship speed according to the output of the main engine
excluding the speed of the current and so on.
Signals surrounding the bottom of the ship are excluded by applying transmission and reception in a
pulse system, thereby preventing errors of the ship speed that occurs due to the change of the draft. In
addition, by using the dual beam system that emits ultrasonic signals in two directions, fore and after,
the ship’s speed errors due to the trim change are dramatically reduced.
This equipment complies with the IMO (International Maritime Organization) regulation and measures
and displays a wide range of ship speed from low speed to high speed.
Four models are available for this equipment, JLN-740A/741A equipped with a 5-inch color display and
JLN-740N/741N equipped with a 4.5-inch monochrome display.
The JLN-740A/740N model is intended for large ships and has a distribution processor that performs
input/output of various signals.
The JLN-741A/741N is a limited model that is intended for small ships and performs minimum
necessary signal output.
Equipment configuration
Equipment
configuration
Components
4 equipment configurations 3 equipment configurations
JLN-740A JLN-740N JLN-741A JLN-741N
Transducer
(NKF-547 or NKF-531E)
   
Signal processor
(NJC-70S)
   
Distribution processor
(NQA-7040)
   
5-inch color display
(NWZ-510SDW)
   
4.5-inch monochrome
display (NWZ-4640)
   