Attitude sensing apparatus

Claim 1

AUTOMATIC LEVELING APPARATUS, COMPRISING: MOUNT MEANS INCLUDING A MOVABLE MEMBER WITH TWO DEGREES OF FREEDOM; AN ATTITUDE RESPONSIVE, ELECTROLYTIC DETECTOR ELEMENT CARRIED BY SAID MOUNT MEANS, SAID ELEMENT HAVING A MOVABLE CONDUCTIVE FLUID AND, EXTENDING INTO SAID FLUID, FOUR INPUT OHMIC BIAS ELECTRODES ARRANGED IN A RHOMBIC PATTERN AND AN OUTPUT OHMIC ELECTRODE CENTRALLY DISPOSED WITH RESPECT TO SAID PATTERN; REFERENCE PHASE BIAS SIGNAL MEANS COUPLED TO A PAIR OF HORIZONTAL AXIS-DEFINING, DIAGONALLY OPPOSED SAID INPUT TERMINALS FOR COUPLING SAID ELEMENT TO A SOURCE OF ALTERNATING CURRENT REFERENCE PHASE BIAS SIGNAL THROUGH SAID FLUID; REFERENCE PHASE BALANCE MEANS COUPLED TO SAID REFERENCE BIAS MEANS AND INCLUDING MEANS FOR ADJUSTING THE VOLTAGE BETWEEN SAID OUTPUT ELECTRODE AND SAID HORIZONTAL AXIS-DEFINING PAIR OF INPUT ELECTRODES; QUADRATURE PHASE BIAS SIGNAL MEANS COUPLED TO THE OTHER PAIR OF ORTHOGONAL HORIZONTAL AXIS-DEFINING, DIAGONALLY OPPOSED INPUT ELECTRODES FOR COUPLING SAID ELEMENT TO A SOURCE OF ALTERNATING CURRENT QUADRATURE PHASE BIAS SIGNAL THROUGH SAID FLUID IN PHASE QUADRATURE WITH SAID REFERENCE BIAS SIGNAL; OUTPUT MEANS COUPLED TO SAID ELEMENTS THROUGH SAID OUTPUT TERMINAL FOR PROVIDING ORTHOGONAL DRIVE CONTROL SIGNALS INDICATIVE TO ERRORS IN LEVEL OF SAID MOUNT MEANS; AND DRIVE MEANS COUPLED TO SAID OUTPUT MEANS AND SAID MOVABLE MEMBER FOR CONTROLLING THE ATTITUDE OF SAID MEMBER IN RESPONSE TO SAID DRIVE CONTROL SIGNALS.