CHAPTER XIX. REMOTE READING COMPASSES 



143. Remote reading mar/vetie compass si/stmu have been intro- 

 duced principally because of the desire to improve the nriagnetic loca- 

 tion of compass elements. Such improvement is particularly impor- 

 tant on small craft because of adjacent machinery and magnetic cargo. 

 Reference is made to the Bureau of Ship's Manual of Engineering In- 

 structions, 1943, Chapter 24, Part 2, paragraphs 24-27 : 



"Auxiliary remote reading magnetic compass systems are sup- 

 ' plied by the Bureau for certain surface craft. These compasses 

 fall into three classes : 



(a) Magnetic compasses, with direct electrical transmission 



to repeaters. 

 (h) Magnetically controlled directional gyros with repeater 



system, 

 (c) Gyro-stabilized induction compasses with repeater 

 system. 



"Complete units will be supplied by the Bureau of Ships. In- 

 structions for installation, operation, and maintenance will accom- 

 pany each instrument. The Engineer Officer shall be responsible 

 for the care and maintenance of this equipment aboard ship." 



The Magnesyn Compass is an example of class (a) above; and, once 

 located in some suitable position, is compensated in a manner similar 

 to the conventional magnetic compass. This compass is used ex- 

 tensively on landing craft and on certain selected combatant vessels. 

 On the latter, the Magnesyn compass system is fitted with compen- 

 sating coils for degaussing. The type coil installation may vary, but 

 should be readily understood upon reference to the installation and 

 maintenance manuals prepared for that particular type coil. 



The slave gyro remote indicating compass is an example of class 

 (b) above. In this compass a directional gyro is slaved; that is, 

 made to precess to the magnetic meridian by a magnetic compass. 

 The repeaters are driven by a selsyn system mechanically connected 

 to the directional gyro. The magnetic compass element of the slave 

 can be corrected for normal coefficients and, under severe conditions, 

 can be corrected for coefficients D and E. Error due to rolling, but not 

 list, is balanced out by the stability of the directional gyro ; whereas, 

 the error due to constant list will introduce deviations on north and 

 south courses. 



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