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Cruise-Speed, Planing
Boat or Universal
Speed Sensor
Note: The Sensor could pick up electro-
magnetic noise. Avoid vicinity of high currents
(battery or battery
cable).
water flow
Attention:
If the fairing has not a
steep leading edge, the
boundary layer might be
diverted towards the pad-
dle wheel!
Installation of a fairing (of non swelling ma-
terial) is recommended on displacement hulls
(not on planing hulls), to place the paddle
wheel outside the boundary layer.
WARNING: The Speed Sensor (or
alternatively the sealing plug) must always be
secured by tightening it firmly, to prevent unin-
tentional retraction by water pressure or other
force.
Airmar CS4500 Ultra-
Sonic Speed Sensor
How the Ultrasonic Speed Sensor
Works
The speed sensor uses ultrasonic pulses
to collect echoes from small particles in the
water as they pass under two transducers
embedded in the insert. These transducers
monitor the particles in their respective
beams. As the boat travels through the water,
both transducers "view" the same stream of
particles.
the instrument calculates the boat speed. The
ultrasonic speed sensor requires particles in
Fairing (not re-
the water to obtain echoes. If the boat is air-
quired for plan-
borne even for a short time or in highly aerat-
ing boats!)
ed water, the sensor will measure an incorrect
speed.
IMPORTANT: The ultrasonic speed sensor
must be in good contact with the water at all
times for the sensor to function properly.
33
Because it takes
time for particles to
travel between the
two transducers, the
aft transducer detects
the particles later
than does the fore
transducer. By mea-
suring this time lapse,
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