Transducer Mounted Inside The Hull - Simrad ES70 - INSTALLATION REV A Installation Manual

Example: Acoustic window
The transducer shown in the figure below is mounted inside the tank behind a strong
acoustic window which could be made of polycarbonate.
The tank is filled with oil.
Figure 34 Acoustic window
A Steel tank
B Oil
C Acoustic
window
D Cable service
loop
E Stuffing tube
F Cable in steel
conduit
Oil inlet
G

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 and clamping rings whenever provided
Circular transducers may be provided with mounting and clamping rings, or with
drawings to allow for local production of these. The mounting ring is welded to the
hole prepared for the transducer, while the clamping ring fits around the edge of the
transducer body. Bolts through the clamping ring into the mounting ring will secure the
transducer between them. Note that several transducers use direction guides to allow
correct mounting.
343522/A
Transducer Installation
131