76 HANDBOOK OF MAGNETIC COMPASS 



3. Check on degaussing system : 



(a) Accuracy of prints of coil installation. 



(h) Check that connection of compass coils to the degauss- 

 ing system will provide a voltage at the control box 

 for each effective degaussing coil (art. 121). These 

 voltages must be : 



(1) Proportional to the degaussing coil effect. 



(2) Reversing with the degaussing circuits. 



(c) Check that leads from each degaussing coil to its com- 

 pass control box are correct, and tag. 



{d) Check each degaussing coil insulation resistance to 

 ground and to all other degaussing coils. 



(e) Insure that sufficient compensating coil circuits are 

 provided for all effective degaussing coils. 



(/) Note whether compass returns to original reading 

 after each degaussing coil had been energized and 

 secured. Try reversal sequence (artj. 128). 



(g) Obtain range instructions, if available, for zone and 

 maximum degaussing coil current settings (ship's 

 degaussing folder). 



108. B. Dockside compensation. — {Compensation is best made with 

 the coils heated to their operating conditions. If any coil requires 

 securing hy reversals, it should he so secured each time during the 

 process of compensation. Record the compensation data on CG-1 

 forms as it is taken. See ofrt. 126.) 



1. Heeling coil procedure. {For any type compass coil in- 

 stallation) : 



{a) Remove compass and balance dip needle in approx- 

 imate location of compass needles, with all degauss- 

 ing coils secured. In the case of the Model "B" mag- 

 nesyn transmitter employing the special mounting 

 bracket, the dip needle should be carefully placed at 

 a height of 2%" above the mounting plate. For 

 Model "A" magnesyn transmitter this distance 

 should be 23/3''. 



(&) Energize M degaussing coil to maximum operating 

 current and note unbalance of the dip needle. 



(c) Adjust current in the H-M (Heeling) compass coil 

 until balance of dip needle is restored. If needle 

 is further unbalanced by increasing the H-M coil 

 current, the H-M coil polarity must be reversed. 

 {Coarse current adjustment is achieved hy placing 



