CHAPTER XII. COMPASS COMPENSATING COIL AND 

 CONTROL BOX DATA 



129. The resistances of different compass compensating coils are 

 tabulated below. A knowledge of these resistances is extremely help- 

 ful in : 



(1) Identifying coil circuits. 



(2) Tracing wiring troubles. 



(3) Calculating current values, 



(4) Associating coil voltages with compass deviations. 



On the basis of these resistance values, and the maximum permis- 

 sible potentiometer current of 1,4 amperes, the table below is expanded 

 to cover tiie maxiinwn permissible voltages which can be placed across 

 different corrector coil windings. Type "T" coils are limited to 1,0 

 amperes. With a knowledge of these limits, a quick check can be made 

 while compensating, or a final check can be made on a complete com- 

 pensation to insure against overload conditions. 



Coil data 



Coil 



Type "B": 



H 



B 



c. ..:. 



c 



Tyue "G": 



H 



NW./SE 



NW./SE 



NE./SW 



NE./SW 



Type "K": 



H 



NW./SE 



NE./SW 



Type "T": 



H 



B (NW./SE) 

 C (NE./SW) 



Number 

 windings 



Mean resist- 

 ance at 80° F. 

 (ohms, per 

 winding) 



1.6 

 1.1 

 1.2 

 .6 



1.6 

 1.2 



.6 

 1.2 



.6 



1.6 



/No. 1 wdg 5. 2 

 tethers... 2.3 

 /No. 1 wdg 5. 2 

 lOthers-.- 2.3 



4.8 

 2.9 

 2.9 



Maximum 

 allowable volt- 

 age per wind- 

 ing at 80° F. 



2.2 

 1.5 

 1.7 



2.2 



1.7 



.8 



2.2 

 /No. 1 wdg. 7. 3 



(Others 3.2 



/No. 1 wdg. 7. 3 

 lOthers 3.2 



4.8 

 2.9 

 2.9 



130. The wiring arrangements of the type "A" control box are 

 illustrated in figure 46, Taps are arranged on the terminal strip to 

 simplify the connection and jumper procedure necessary for con- 

 trolling coil currents. The fixed resistor combinations which are in 

 series with the variable resistor may be connected in series or parallel, 

 as desired, in order to obtain more delicate current control. The maxi- 



639720—45- 



10,^ 



