Simrad ES38-12 - REV C, Installation Manual, Page: 20 / 46

Simrad ES38-12
Example: Acoustic window
Figure 11 Acoustic window A Steel tank
B Oil
C Acoustic window
D Cable service loop
E Stuffing tube
F Cable in steel conduit
G Oil inlet
The transducer shown in the figure is
mounted inside the tank behind a strong
acoustic window.
The window is typically made of
polycarbonate. The tank is filled with oil.
Transducer mounted inside the hull
The transducer can also be mounted inside the hull.
An installation of the transducer inside the hull, and sounding through the hull, requires a
good acoustic contact between the transducer face and the hull. Build a tank around the
transducer and fill it with a liquid. Oil used in hydraulic systems is a well suited liquid
for this purpose. It contains no gas bubbles and is non-corrosive.
Typical values of the two way loss are 3 dB for polyester, 6 dB for aluminium and 10 dB
for steel. Hulls made of wood or a sandwich type with foam in the middle, attenuate
the sound so much that through hull sounding must be regarded as impossible. The loss
varies with the distance between transducer face and the hull. The best result is obtained
when the distance is half a wavelength. Consult Simrad for advice. In addition to the
loss, the beam pattern is degraded, because a larger area of the hull is set into vibrations.
Use mounting plate whenever provided
Certain transducers may be provided with a mounting plate, or with drawings to allow
for local production of this.
The mounting plate is welded to the hole prepared for the transducer. Bolts through the
transducer body into the mounting plate will secure the transducer.
Smooth surface is important
Mounting screws or bolts must not be extruding from the transducer or the area
immediately around it.
18
344276/A