Wordnet 3.0
NOUN (1)
1. 
 an arrangement of coils used in sensitive electrical instruments; 
 the coils are arranged to give zero resultant external magnetic field when a current passes through them and to have zero electromotive force induced in them by an external magnetic field; 
WordNet (r) 3.0 (2006):
astatic coils
    n 1: an arrangement of coils used in sensitive electrical
         instruments; the coils are arranged to give zero resultant
         external magnetic field when a current passes through them
         and to have zero electromotive force induced in them by an
         external magnetic field