Installation manual

Transducer installation

851-165187 / Rev.A

Transducer location

General

A single answer to the question where to locate the transducer

cannot be given. It depends very much on the vessel’s

construction. However, there are some important guide lines.

Go deep

The upper water layers of the sea contain a myriad of small air

bubbles created by the breaking waves. In heavy seas the

uppermost 5 to 10 metres may be air-filled, with the highest

concentrations near the surface. Air bubbles absorb and reflect

the sound energy, and may in worst cases block the sound

transmission totally. Therefore, mount the transducer at a deep

position on t he hull.

Consider the situation when the vessel is unloaded, and when it

is pitching in heavy seas. The transducer must never be lifted

free of the water surface. Not only will the sound transmission

be blocked, but the transducer may be damaged by slamming

against the sea surface.

Another reason to go deep is cavitation in front of high power

transducers. Cavitation i s t he formation of small bubbles in the

water due to the resulting local pressure becoming negative

during parts of the acoustic pressure cycles. The cavitation

threshold increases with the hydrostatic pressure.

Vessel heave

Heave is the up and down movement of the vessel. It disturbs

the echo traces in the echogram, so that a flat bottom is

displayed as a wave. A transducer location in the middle of the

vessel minimises the influence of vessel roll and pitch.

Noises from protruding objects on the hull

Objects protruding from the hull, such as zinc anodes, sonar

transducers or even the vessel’s keel, generate turbulence and

flow noise. Also holes and pipe outlets are noise sources. They

may act as resonant cavities amplifying the flow noise at certain

frequencies. Do not place an echo sounder transducer in the

vicinity of such objects, and especially not close behind them.

For the same reason, it is very important that the hull area

around the transducer face is as smooth and level as possible.

Even traces of sealing compound, sharp edges, protruding bolts

or bolt holes without filling compound will create noise.