130 HANDBOOK OF MAGNETIC COMPASS 



II. Theory of magnetic compass adjustment — Continued. 



C Induced magnetic effects — Continued. 



5. Unsymmetrical distribution of horizontal soft iron, A — constant devia- 

 tion on all headings, 

 (a) Does not vary with latitude. 



D. Correction for induced magnetic effects — Use soft iron correctors. 



1. Vertical component — heeling magnet (exception). 



2. Vertical resultant — Flinders bar. 



3. Quadrantal deviation — spheres. 



E. Constant error. A: 



1. Human error in calculations. 



2. Physical misalignments. 



3. Magnetic effects. 



F. Interaction of magnetic correctors : 



1. Heeling magnet and Flinders bar. 



2. Magnetized spheres or Flinders bar. 



3. Compass needle induction in spheres. 



4. Flinders bar creates plus D error. 



5. Slewing bar creates E error. 



6. Flinders bar and fore-and-aft B magnets. 



7. Spheres and permanent magnets. i 



G. Residual Deviation Curve : 



1. Specify corrector positions. 



2. Possible changes. 



(a) Improper Flinders bar adjustment. 



(&) Change in directive force. 



(c) Heeling with latitude. 



((f) Deperming. 



(e) Gyro repeater, doors, guns, etc. 



III. Practice session : 



A. Become familiar with different binnacles and corrector arrangements. 



B. Observe the effects of different magnets, spheres, and Flinders bar cor- 



rectors while the ship is on different compass headings. 



C. Check spheres and Flinders bar for magnetization. 



IV. Theory of magnetic compensation (See ch. XI) : 



A. Degaussing coil effects — Electro-magnetic effects: 



1. Type degaussing coils. 



2. Ampere-turn rating. 



3. Location of compass. 



4. Steel distribution. 



B. Correction for degaussing coil effects — Use coils : 



1. Types of compass compensating coils. 



2. Vector components. 



C. Connection to degaussing systems : 



1. Must provide a voltage which is — 



(a) Proportional to degaussing current. 

 (6) Reversible with degaussing current. 



D. Control boxes : 



1. Potentiometer circuit with coarse and fine resistor adjustments. 



E. Relation of compass compensation to compass adjustment : 



1. Flinders bar coil utilizes Flinders bar as iron core. 



2. Sphere coils are dependent upon s-ize and position of quadrantal 



spheres. 



