COMPENSATION CHECK-OFF LIST 79 



(c) Energize M degaussing coil to maximv/m operating 

 current, and note deviation of the compass. (See 

 note at end of art. 108.) 

 {d) Adjust current in the NW./SE.-M compass coil until 

 compass returns to original position. If increasing 

 the current in this coil creates a greater deviation, re- 

 verse the NW./SE.-M compass coil polarity. ( Coarse 

 and fine adjustments are achieved as noted under 

 Heeling Coil Procedure.) 

 {e) Be sure that final setting would not permit more than 

 1.4 amperes to flow through the variable control re- 

 sistor, at maximum degaussing coil current. This 

 is approximately equivalent to 1.7 volts per winding 

 across NW./SE.-M (three-winding) compass coil. 

 (/) Repeat (c), {d)^ and (e) for all other degaussing coils 

 (F, Q, A) individually^ while compass is still de- 

 deflected to 135° or 315°. Correct each with 

 NW./SE.-F, NW./SE.-Q, and NW./SE.-A coil 

 windings, respectively. 

 {g) Deflect compass card to 045° or 225° heading, which- 

 ever is closer, with all degaussing coils secured. 

 (A) Energize M degaussing coil to maximum operating 



current, and note deviation of the compass. 

 {i) Adjust current in the NE./SW.-M compass coil until 



compass returns to original position. 

 {j) Limit coil current, as in {e) above. 

 {k) Repeat (A), (i), and {j) for all other degaussing coils 

 (F, Q, A) individually, while compass is still de- 

 flected to 045° or 225°. Correct each with 

 NE-./SW.-F, NE./SW.-Q, and NE./SW.-A com- 

 pass coil windings, respectively. 

 (0 Now that the H, NW./SE,, and NE./SW. components 

 are compensated for each degaussing coil, check that 

 all coil connections and jumpers are secured. Then 

 repeat the entire process for the refinement of each 

 component because voltage drops, coil misalign- 

 ments, and interaction of vector effects create pos- 

 sible discrepancies on the first approximation. (See 

 art. 124.) 

 Note.— This dockside compensation is subject to errors from welding, passing 

 cranes, swaying of ship, adjacent ships, and shore interferences. If a degauss- 

 ing coil ever creates a deviation which is over 90°, or makes compensation diffi- 

 cult, energize the degaussing coil with reversed polarity and compensate as 

 usual. Another good rule is to always compensate the largest component ef- 

 fect first. 



