Transducer installation inside the hull
The transducer can be mounted inside the hull. This installation method forces the transducer to send and receive the acoustic pulses through the hull plating. This requires a good acoustic contact between the transducer face and the hull.
In order to install the transducer like this, you must design and build a tank around the transducer. The tank must be filled with a liquid. Hydraulic oil is well suited for this purpose. It contains no gas bubbles and is non-corrosive.
Note
Placing the transducer inside the hull will reduce the transmit power and the reception sensitivity.
Typical values of the two way loss are 3 dB for polyester, 6 dB for aluminium and 10 dB for steel.
The loss varies with the distance between transducer face and the hull. The best result is obtained when the distance is half a wavelength.
In addition to the loss, the beam pattern is degraded, because a larger area of the hull is set into vibrations.
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.
If this is your only option for transducer installation, consult Kongsberg Maritime for advice.
The transducer shown in the figure below is mounted inside the hull. The tank is filled with oil.
Image
A Steel tank
B Oil
C Hull plating
D Cable service loop
E Bushing
F Cable in steel conduit
G Hole for oil filling
H Air outlet
Using the mounting ring
This large circular is transducer is designed to be mounted using the integrated flange and a mounting ring.The mounting ring is welded to the hole prepared for the transducer. Bolts through the transducer flange into the mounting ring will secure the transducer in place.
Note
Make sure that the "Forward" direction on transducer points in the forward direction of the vessel.
A suitable mounting ring can be provided by Kongsberg Maritime. A drawing is available for local manufacturing. End user manuals and source drawings (normally in AutoCad format) can be downloaded from our website.
Smooth surface is important
Make sure that the surface of the transducer face, as well as the plating and putty around the transducer is as even and smooth as possible.Obstructions on these surfaces will create problems with turbulent flow, and may cause noise.
Mounting screws or bolts must not be extruding from the transducer or the plating immediately around it.
Note
Obstructions on these surfaces will create problems with turbulent flow, and may cause noise.