Null-flux transducer for use in electrical measuring and control systems

Claim 1

A TRANSDUCER HAVING A MAGNETIC CIRCUIT COMPRISING: SATURABLE CORE MEANS INCLUDING A RING-SHAPED PORTION HAVING A DRIVING WINDING THEREON, A PAIR OF SPACED POLE PIECES PROJECTING FROM SAID SATURABLE CORE MEANS, INPUT MEANS FOR PRODUCING AN M.M.F. TO ESTABLISH A VARIABLE FLUX LEVEL IN SAID MAGNETIC CIRCUIT, BIAS MEANS ASSOCIATED WITH SAID PAIR OF POLE PIECES FOR PRODUCING PREDETERMINED OPPOSING FLUX IN OPPOSITION TO THE ESTABLISHED VARIABLE FLUX IN SAID MAGNETIC CIRCUIT TO PROVIDE A REFERENCE FLUX LEVEL FOR SAID INPUT MEANS AT WHICH THE OUTPUT FROM SAID TRANSDUCER IS ZERO, AN OUTPUT WINDING ON A PORTION OF SAID MAGNETIC CIRCUIT RESPONSIVE TO A NET FLUX LEVEL OTHER THAN ZERO TO PRODUCE A SIGNAL, A FEEDBACK WINDING ON SAID PAIR OF POLE PIECES, AND AMPLIFYING MEANS HAVING ITS INPUT CIRCUIT CONNECTED TO SAID OUTPUT WINDING AND ITS OUTPUT CONNECTED TO SAID FEEDBACK WINDING TO RESTORE THE NET FLUX LEVEL SUBSTANTIALLY TO ZERO IN RESPONSE TO SAID SIGNAL.