108 



HANDBOOK OF MAGNETIC COMPASS 



(6) Load coil windings sensibly so as to avoid over-heating. 



(7) Connect two or more windings in series if one winding 

 is inadequate. 



Compensation may be set up approximately by the use of these 

 curves, but it is to be remembered that thermal resistance changes in 

 the compensating coils, and the fact that different compass needle 

 arrays are affected differently by similar coils, limit the accuracy of 

 this method. 



O-S' 

 LOAD ON COIL 



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FiGURH 57. 



These curves are taken on a Navy Standard^ compass with Navy 

 Standard binnacle equipment. Different binnacle dimensions which 

 alter coil spacings and different compass needle arrays will alter the 

 data somewhat. The deviations are as observed for a specified di- 

 rective force, but conversion can be made to any desired directive 

 force inasmuch as the strength of a coil effect is 'proportional to the 

 tangent of the angle of deviation. 



