78 HANDBOOK OF MAGNETIC COMPASS 



is approximately equivalent to 1.5 volts per wind- 

 ing across B-M compass coil. 



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

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

 flected to 090° to 270°. Correct each with B-F, B-Q,' 

 and B-A coil windings, respectively. 



{h) Deflect compass card to 000° or 180° heading, which- 

 ever is closer, with all degaussing coils secured. 



(^) Energize M degaussing coil to maximum operating 

 current, and note the deviation of the compass. 



(_/') Adjust current in the C-M (sphere) compass coils 

 until compass returns to original position. 



(k) If correction is difficult, check: 



(1) Bucking sphere coil windings. 



(2) Need for more windings. 



(Z) Be sure that final setting would not permit more than 

 1.4 amperes to flow through the variable control re- 

 sistor, at maxirmurm degaussing coil current. This 

 is approximately equivalent to 0.8 volt per winding 

 across C-M (two winding) coils. 



(m) Repeat (^), (^'), (A;), and {I) for all other degaussing 

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

 deflected to 000° or 180°. Correct each with C-F, 

 C-Q, and C-A coil windings, respectively. 



{n) Now that the H, B, and C components are compen- 

 sated for each degaussing coil, check that all coil 

 connections and jumpers are secured. Then repeat 

 the entire process for the refinement of each com- 

 ponent because voltage drops, coil misalignments, 

 and interaction of vector effects create possible dis- 

 crepancies on the first approximation. (See art. 

 124.) 



3. Type "G" compensating coil procedures. {Type "^ST" coil 

 procedure or intercardinally mounted type "7^" coil pro- 

 cedure is the same^ except for voltage limitations noted 

 in art. 129. Heeling adjustments for amy type coils are 

 made as in Section B-1 of this Check-off list) : 



{a) Replace the dip needle with regular compass. 



(6) Deflect compass card to 135° or 315° heading, which- 

 ever is closer, with all degaussing coils secured (art. 

 125). 



