Cours sur les méthodes d'évaluation acoustique ... - Fao - Copemed

Calibration2 CALIBRATION PROCEDURECheck the hardware installationCheck that the transducer cable is connected to the correct transducer plugon the rear side of the EK 500 / EY 500.Check the internal test oscillatorSelect the Transceiver Menu and set Mode to Test.Select the Operation Menu and set Ping Mode to Normal and Noise Marginto 0 dB.Select the Test Menu/Transceiver.The amplitude of the internal test oscillator is now displayed. It should be-55 dB ±2 dB re 1W on a split-beam sounder and -61 dB ±2 dB re 1W on asingle-beam sounder. If the amplitude is outside these limits, disconnect thetransducer cable and check the amplitude to see if the fault is in thetransducer or in the receiver. The amplitude should now be -49 dB ±2 dB re 1W on a split beam sounder, and -55 dB ±2 dB re 1 W on a single beamsounder. If the amplitude is still outside the limits, the problem isprobably related to the receiver. If it is inside the limits, the transducerimpedance should be checked.RiggingThe following rigging description is to a great extent reproduced fromICES report 144. The vessel should be anchored in calm and shelteredwater. The depth must be sufficient for separation of sphere and bottomechoes. It is desirable, moreover, to work in water as deep as possible,consistent with maintaining a stable platform. Both bow and sternanchoring or tying are recommended. This is illustrated in figure 1.Placing of winchesWinches should be used to guide and steer lines to the sphere for itscentering in the echo sounder beam. Affix these winches to the deck railingin accordance with detailed ship drawings. Place the first winch in thetransverse plane of the vessel running through the transducer. If thetransducer is mounted on one side of the keel, place the first winch on theopposite side of the vessel. Place the second and third winches on the samevessel side as the transducer and at equal distances from the transversesection containing the transducer and first winch.Each winch must be provided with a long spool of 0.60 mm diametermono- filament nylon line, which is marked with small swivels at 5 mintervals, beginning 10 m from the loose end.4 P2260/E