Display Function - Marine Autopilots, Engine Controls and Instruments

Cruise-Speed, Planing
Boat or Universal
Speed Sensor
Note: The Sensor could pick up electromagnetic
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 paddle
wheel!
Fairing (not required
for planing
boats!)
Installation of a fairing (of non swelling material)
is recommended on displacement hulls
(not on planing hulls), to place the paddle
wheel outside the boundary layer.
15...20mm
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.
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 measuring
this time lapse,
the instrument calculates the boat speed. The
ultrasonic speed sensor requires particles in
the water to obtain echoes. If the boat is airborne
even for a short time or in highly aerated
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.
!
WARNING: The Speed Sensor (or alternatively
the sealing plug) must always be
secured by tightening it firmly, to prevent
unintentional retraction by water pressure or
other force.
33