Kongsberg Simrad ST90, Reference Manual

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manual operation, read carefully through the relevant operating procedures. You must
familiarize yourself with the correct handling methods and the relevant safety requirements.
Hull Unit Lowering depth (m) Transducer cable (m) Maximum speed
(knots)
4.6 ST92 1.2
7
21
4.6 ST93 1.6
7
16
4.6 ST94 2.1
7
11
On some vessels, additional transducer protection is required. One example is vessels
working in arctic conditions. It is important for them to prevent ice from damaging the
transducer. A gate valve is then added to the hull unit installation. By means of a mechanical
construction it shuts off the bottom of the installation trunk when the ST90 system is not
used.
For more information, refer to the end-user documentation provided by the manufacturer.
Related topics
Simrad ST90, page 17
System units, page 23
Lowering and hoisting the transducer from the sonar room, page 187
Transducer
The cylindrical transducer allows the sonar beam to provide a full 360 degrees coverage of
the water volume.
The transducer converts the electric energy generated by the transmitter circuitry to physical
vibrations. These vibrations alter the water pressure, and create an acoustic pulse that is
sent into the water. The acoustic signal is transmitted as a beam. The duration of the
acoustic pulse, as well as its frequency and shape, are controlled by the system software.
The direction and opening angle of the beam is controlled by the transmitter circuitry and
the physical properties of the transducer. After the transmission, the transducer works as
a "microphone". It converts the water pressure created by the acoustic echoes to electric
energy. These weak echo signals are sent to the amplifiers in the receiver circuitry.
Simrad ST90 Reference Manual