Page 47 - Electronic Navigation Cyber Book
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The majority of Doppler logs in use are pulse systems
Transducers
The angle of the along ships beams is about 3 deg., that of the
athwart ships beam is about 8 degrees.
The frequency used is 100 to 600 kHz – newer models have a
transmission frequency of maybe 2 MHz.
2
The surface area of each transducer need then be only about 10 cm .
The high frequency and the concave shape of the surface also lead to a
small beam angle.
The higher frequency influences the reflection and the absorption but not
the speed of propagation.
The transducers are of the electrostnctive type.
Two possibilities for a Janus configuration.
Usually the transducers are inserted in a 'sea chest' or 'sea
well’, permitting their removal for repairs or replacement without the ship
requiring dry-docking.
The diameter of the hole required in the hull plates is about 350 mm.
Replacement of a transducer (1) in a sea chest without the ship being
dry-docked can be done in the following way.
© 2018 Digital Galaxy Index 47
