Airmar 300WX Installationshandbuch PDF herunterladen (Seite 28)

CA/CR40/42/50/52 Installation manual Chapter 11

poor performance. Due to the varying design of ship’s hulls and different

operating speeds, there can be great variation in the amount of air bubbles which

are carried beneath the hull. These bubbles tend to be carried close to the hull as

they pass aft. For this reason, it is desirable for the transducer to be mounted on a

fairing block which holds the transducer away from the hull and which directs

the flow of aerated water around the sides of the transducer rather than over the

face of the transducer.

On deep keeled vessels, care must be taken to ensure that the transducer beam

will not be blocked by any part of the keel. Although the appropriate mounting

location that meets all requirements depends on the type of vessel and its normal

operating speeds, a practical choice is usually somewhere between one third and

one half of the vessel’s water line length from the bow. Leveling blocks may be

designed accordingly to meet this requirement.

) The more the transducer protrudes from the hull, the better the results will be.

Particularly the lower frequency operation, interference from propeller noise can

be a significant problem. This can be seen as an increase in the “noise” on the

echosounder display when the propeller speed is increased. To help reduce this,

the transducer'’ mounting face may be angled slightly forward on the order of 5°

for the 50 kHz transducers and 3° for the 200 kHz transducers. The goal is to

incline the transducer so that a line of sight along the transducer’s radiating

surface passes below the propeller.

) Keeping the propeller clean and free of any nicks or roughness will assist in

minimizing interference from propeller noise due to cavitation.

Sources of noise to consider:

Water/air noise Acoustic noise Electrical noise

Air bubbles

Turbulence

Propeller

Main engine

Reduction gear

propeller shaft

Generators

auxiliary engines

Power plant for freezers

Hydraulic pumps

Rudder engine

Bow thruster

Stern thruster

Noise from electrical cables

Noise from generators

Poor grounding of instrument

Radiated noise from other

instruments

Dc – Dc converters

Electrical winches

Neon lights

etc.

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