Simrad FS70 -, Руководство оператора

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FS70 Trawl Sonar System
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974-24007001/5.0
interfaced to echo sounders or other onboard equipment. The head rope depth information
appears on the sounder showing the location of the trawl in relation to the fish or bottom
returns.
1.12 Trawl Cable, Winch and Block
The trawl cable and the associated equipment are supplied by the vessel. The trawl cable is
chosen for maximum mechanical strength, durability and minimum attenuation of the
signals. Cables in common use are coaxial with breaking points of 1500kg and 6000kg.
Cable winches are delivered in different types and with different capacities; low-pressure
hydraulic, high-pressure hydraulic and electrically driven. Choice of winch is dependent on
prevailing conditions; type and length of cable and available source of power. Most types
operate automatically - the cable is pulled out, kept tight during towing, and hauled in
together with the trawl. Control of the winch is done remotely from the bridge.
Any commercially available pulley block may be used to properly align the cable onto the
winch. A snatch block has the advantage that it may be installed without having to thread
the cable through it. A unit with two movable steering arms (one on each side of the pulley)
is recommended to prevent the cable from coming off the pulley and causing damage to the
cable.
2 Theory of Operation
2.1 Introduction
This section explains the theory of operation of the Vertical and Sounder Scanning Trawl
Monitoring Sonar System.
2.2 Basic Principles

Sound waves travel very efficiently through water.

A sound pulse can be projected through water in a controlled direction with the sonar
transducer.

An object in the path of the projected sound pulse will reflect some sound pulses back
toward the sonar transducer.

The speed of the sound pulse projected through the water can be predicted for given
conditions.