CHAPT06 - CHAPTER 6 MAGNETIC COMPASS ADJUSTMENT GENERAL...

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81 CHAPTER 6 MAGNETIC COMPASS ADJUSTMENT GENERAL PROCEDURES FOR MAGNETIC COMPASS ADJUSTMENT 600. Introduction This chapter presents information and procedures for magnetic compass adjustment. Sections 601 and 613 cover procedures designed to eliminate compass errors satisfactorily. Refer to Figure 607 for condensed infor- mation regarding the various compass errors and their correction. The term compass adjustment refers to any change of permanent magnet or soft iron correctors to reduce normal compass errors. The term compass compensation refers to any change in the current slupplied to the compass compen- sating coils to reduce degaussing errors. 601. Adjustment Check-Off List If the magnetic adjustment necessitates (a) movement of degaussing compensating coils, or (b) a change of Flinders bar length, check also the coil compensation per section 646. Expeditious compass adjustment depends on the appli- cation of the various correctors in an optimum sequence designed to minimize the number of correction steps. Cer- tain adjustments may be made conveniently at dockside, simplifying the at sea adjustment procedures. Moving the wrong corrector wastes time and upsets all previous adjustments, so be careful to make the correct ad- justments. Throughout an adjustment, special care should be taken to pair off spare magnets so that the resultant field about them will be negligible. To make doubly sure that the compass is not affected by a spare magnet’s stray field, keep them at an appropriate distance until they are actually inserted into the binnacle. A. Dockside tests and adjustments. 1. Physical checks on the compass and binnacle. a. Remove any bubbles in compass bowl (section 610). b. Test for moment and sensibility of compass nee- dles (section 610). c. Remove any slack in gimbal arrangement. d. Magnetization check of spheres and Flinders bar (section 610). e. Alignment of compass with fore-and-aft line of ship (section 610). f. Alignment of magnets in binnacle. g. Alignment of heeling magnet tube under pivot point of compass. h. See that corrector magnets are available. 2. Physical checks of gyro, azimuth circle, and peloruses. a. Alignment of peloruses with fore-and-aft line of ship (section 610). b. Synchronize gyro repeaters with master gyro. c. Ensure azimuth circles and peloruses are in good condition. 3. Necessary data. a. Past history or log data which might establish length of Flinders bar (sections 610 and 623). b. Azimuths for date and observer’s position (section 633 and Chapter 17). c. Ranges or distant objects in vicinity if needed (lo- cal charts). d. Correct variation (local charts). e. Degaussing coil current settings for swing for resid- ual deviations after adjustment and compensation (ship’s Degaussing Folder). 4. Precautions. a. Determine transient deviations of compass from gyro repeaters, doors, guns, etc. (sections 636 and 639).
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This note was uploaded on 10/25/2010 for the course HYDROGRAPH hydrograph taught by Professor Kolmogrov during the Spring '10 term at Universitas Katolik Parahyangan.

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CHAPT06 - CHAPTER 6 MAGNETIC COMPASS ADJUSTMENT GENERAL...

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