Circuit using alternating voltage transducers

Claim 1

DIRECT CURRENT APPARATUS FOR SENSING A PHYSICAL CONDITION WITH A VARIABLE IMPEDANCE TRANSDUCER EXCITED BY AN ALTERNATING VOLTAGE COMPRISING, IN COMBINATION, A SOURCE OF DIRECT VOLTAGE, A VOLTAGE CONVERSION MEANS, SAID VOLTAGE CONVERSION MEAND HAVING A PAIR OF POWER INPUT TERMINALS AND A PAIR OF OUTPUT TERMINALS AND BEING ADAPTED TO CONVERT A DIRECT VOLTAGE APPLIED TO ITS POWER INPUT TERMINALS TO AN ALTERNATING VOLTAGE AT ITS POWER OUTPUT TERMINALS, MEANS CONNECTING SAID POWER INPUT TERMINALS TO SAID VOLTAGE SOURCE, SAID CONNECTING MEANS INCLUDING AT LEAST ONE IMPEDANCE ELEMENT IN SERIES BETWEEN SAID SAID CONVERTER AND SAID SOURCE, A VARIABLE IMPEDANCE TRADUCER ADAPTED FOR ALTERNATING VOLTAGE EXCITATION, MEANS CONNECTING SAID TRANSDUCER TO THE OUTPUT TERMINALS OF SAID VOLTAGE CONVERSION MEANS, CHANGES IN IMPEDANCE OF SAID TRANSDUCER BEING REFLECTED AS VARIATIONS IN THE INPUT IMPEDANCE OF SAID CONVERSION MEANS, AND DIRECT CURRENT MEASURING MEANS, RESPONSIVE TO CURRENT VARIATIONS IN THE SERIES CIRCUIT INCLUDEING SAID CONVERSION MEANS AND SAID IMPEDANCE ELEMENTS RESULTING FROM VARIATIONS IN SAID TRANSDUCER IMPEDANCE.