Densimetering systems

Claim 1

A DENSITY TRANSDUCER FOR PROVIDING AN ALTERNATING ELECTRICAL SIGNAL HAVING A FREQUENCY WHICH IS VARIABLE IN A KNOWN MANNER WITH THE DENSITY OF A FLUID, A HOLLOW MEMBER HAVING A THIN WALL, THE EXTERNAL SURFACE OF WHICH IS A SURFACE OF REVOLUTION, A TORSION SHAFT AXIALLY MOUNTED IN SAID HOLLOW MEMBER, A RADIALLY EXTENDING BLADES FIXEDLY SECURING THE INNER WALL OF SAID HOLLOW MEMBER TO SAID SHAFT; A HOLLOW CASING COMPLETELY ENCLOSING SAID MEMBER WHEREBY AN ANNULAR GAP IS FORMED BETWEEN THE EXTERNAL SURFACE OF SAID HOLLOW MEMBER AND THE INTERNAL SURFACE OF SID CASING, SAID GAP HAVING A WIDTH GREATER THAN ONEHALF OF THE WAVE LENGTH CORRESPONDING TO SAID ALTERNATING SIGNAL; MEANS FIXEDLY SECURING THE ENDS OF SAID SHAFT TO SAID CASING WHEREBY SAID FLUID CAN FREELY FLOW THROUGH SAID CASING, SAID MEANS, AND SAID HOLLOW MEMBER; AN EXCITER EXERTING AN ALTERNATING TORQUE ON SAID SHAFT THEREBY IMPARTING A RELATIVE ALTERNATING VELOCITY BETWEEN SAID MEMBER AND SAID CASING, A DETECTOR RESPONSIVE TO SAID RELATIVE VELOCITY FOR PORVIDING SAID VARIABLE FREQUENCY ELECTRICAL SIGNAL, AND AN AMPLIFIER HAVING AN INPUT CIRCUIT COUPLED TO SAID DETECTOR AND AN OUTPUT CIRCUIT COUPLED TO SAID EXCITER FOR MAINTAINING SAID RELATIVE VELOCITY.