Second harmonic magnetometer having a plurality of transducers in combination with means responsive to flux amplitude and direction

Claim 1

A FLUX-GATE TYPE MAGNETIC FIELD DETECTOR COMPRISING: AT LEAST ONE SENSING TRANSDUCER AND A REFERENCE TRANSDUCER EACH HAVING A MAGNETICALLY PERMEABLE ELEMENT, A PAIR OF BALANCED DRIVING WINDINGS, AND A PAIR OF OUTPUR WINDINGS, SAID SENSING TRANSDUCER BEING EXPOSABLE TO EXTERNAL MAGNETIC FIELDS FOR SENSING THEREOF, AND SAID REFERENCE TRANSDUCER HAVING BIAS MEANS FOR MAGNETICALLY BIASING ITS RESPECTIVE MAGNETICALLY PERMEABLE ELEMENT, SAID REFERENCE TRANSDUCER BEING SHIELDED AGAINST EXTERNAL MAGNETIC FIELDS; A DRIVING SOURCE OF ALTERNATING CURRENT OF A FIRST FREQUENCY COUPLED TO SAID DRIVING WINDINGS OF SAID SENSING AND REFERENCE TRANSDUCERS; SAID OUTPUT WINDINGS OF SAID REFERENCE TRANSDUCER EXHIBITING A REFERENCE OUTPUT SIGNAL OF A PREDETERMINED AMPLITUDE AND OF A SECOND FREQUENCY WHICH IS SUBSTANTIALLY DOUBLE SAID FIRST FREQUENCY; SAID OUTPUT WINDINGS OF SAID SENSING TRANSDUCER EXHIBITING A SENSED OUTPUT SIGNAL UPON THE PRESENCE OF AN EXTERNAL MAGNETIC FIELD, SAID SENSED OUTPUT SIGNAL BEING OF SAID SECOND FREQUENCY, AND HAVING AN AMPLITUDE WHICH IS A FUNCTION OF THE INTENSITY OF SAID EXTERNAL MAGNETIC FIELD BEING PRESENT, AND HAVING A PHASE RELATIONSHIP WITH SAID REFERENCE OUTPUT SIGNAL WHICH IS A FUNCTION OF THE POLARITY OF SAID EXTERNAL MAGNETIC FIELD RELATIVE TO SAID BIAS MEANS; AND MEANS COUPLED TO SAID OUTPUT WINDINGS OF SAID SENSING AND REFERENCE TRANSDUCERS FOR INDICATING THE PRESENCE OF SAID EXTERNAL MAGNETIC FIELD AS A FUNCTION OF THE AMPLITUDES AND PHASE RELATIONSHIP OF SAID REFERENCE OUTPUT SIGNAL AND SAID SENSED OUTPUT SIGNAL.