Solid state capacity servo measuring system utilizing inductive feedback

Claim 1

A SYSTEM FOR MEASURING THE VOLUME OF A LIQUID STORED IN A CONTAINER OF KNOWN DIMENSIONS, COMPRISING A SOURCE OF CONSTANT AMPLITUDE A.C. VOLTAGE, A HIGH-GAIN A.C. AMPLIFIER HAVING A PAIR OF INPUT TERMINALS AND A PAIR OF OUTPUT TERMINALS, A CAPACITANCE BRIDGE HAVING TWO ARMS AND CONNECTED BETWEEN SAID SOURCE AND THE INPUT TERMINALS TO SAID AMPLIFIER, SAID BRIDGE CIRCUIT COMPRISING A CAPACITOR IN EACH ARM THEREOF, THE CAPACITOR IN ONE ARM THEREOF HAVING A FIXED VALUE AND THE CAPACITOR IN THE OTHER ARM HAVING A VALUE VARIABLE BETWEEN UPPER AND LOWER LIMITS IN DEPENDENCE ON, AND PROPORTIONAL TO, ANY CHANGE IN SAID PARAMETER, THE LOWER OF SAID LIMITS HAVING A VALUE EQUAL TO THE FIXED VALUE OF THE CAPACITOR IN SAID ONE ARM, AND A TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING, THE PRIMARY WINDING BEING CONNECTED IN THE ONE ARM OF SAID BRIDGE CIRCUIT BETWEEN THE CAPACITOR THEREIN AND ONE OF SAID AMPLIFIER INPUT TERMINALS, A TAPPING POINT ON SAID SECONDARY WINDING DIVIDING SAID SECONDARY WINDING INTO TWO PORTIONS, ONE OF SAID PORTIONS BEING CONNECTED BETWEEN SAID OUTPUT TERMINALS OF THE AMPLIFIER, A FURTHER CAPACITOR, SAID FURTHER CAPACITOR BEING CONNECTED IN SERIES WITH THE OTHER PORTION OF SAID TRANSFORMER BETWEEN SAID ONE INPUT TERMINAL OF THE AMPLIFIER AND AN OUTPUT TERMINAL OF SAID AMPLIFIER, SAID FURTHER CAPACITOR AND SAID TRANSFORMER COMPRISING A FEEDBACK LOOP FOR SAID AMPLIFIER AND ARRANGED TO REDUCE TOWARDS ZERO THE INPUT CURRENT TO SAID AMPLIFIER WHEREBY THE VOLTAGE AT THE OUTPUT TERMINALS OF SAID AMPLIFIER IS RENDERED PROPORTIONAL TO THE VARIABLE VALUE OF THE CAPACITOR IN SAID OTHER ARM OF THE BRIDGE.

Claim 2

A SYSTEM FOR MEASURING THE VOLUME OF A LIQUID STORED IN A CONTAINER OF KNOWN DIMENSIONS, COMPRISING A SOURCE OF CONSTANT AMPLITUDE A.C. VOLTAGE, A HIGH-GAIN A.C. AMPLIFIER HAVING A PAIR OF INPUT TERMINALS AND A PAIR OF OUTPUT TERMINALS, A CAPACITANCE BRIDGE HAVING TWO ARMS AND CONNECTED BETWEEN SAID SOURCE AND THE INPUT TERMINALS TO SAID AMPLIFIER, SAID BRIDGE CIRCUIT COMPRISING A CAPACITOR IN EACH ARM THEREOF, THE CAPACITOR IN ONE ARM THEREOF HAVING A FIXED VALUE AND THE CAPACITOR IN THE OTHER ARM HAVING A VALUE VARIABLE BETWEEN UPPER AND LOWER LIMITS IN DEPENDENCE ON, AND PROPORTIONAL TO, ANY CHANGE IN SAID PARAMETER, THE LOWER OF SAID LIMITS HAVING A VALUE EQUAL TO THE FIXED VALUE OF THE CAPACITOR IN SAID ONE ARM, AND A TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING, THE PRIMARY WINDING BEING CONNECTED IN THE ONE ARM OF SAID BRIDGE CIRCUIT BETWEEN THE CAPACITOR THEREIN AND ONE OF SAID AMPLIFIER INPUT TERMINALS, A TAPPING POINT ON SAID SECONDARY WINDING DIVIDING SAID SECONDARY WINDING INTO TWO PORTIONS, ONE OF SAID PORTIONS BEING CONNECTED BETWEEN SAID OUTPUT TERMINALS OF THE AMPLIFIER, A FURTHER CAPACITOR, SAID FURTHER CAPACITOR BEING CONNECTED IN SERIES WITH THE OTHER PORTION OF SAID TRANSFORMER BETWEEN SAID ONE INPUT TERMINAL OF THE AMPLIFIER AND AN OUTPUT TERMINAL OF SAID AMPLIFIER, SAID FURTHER CAPACITOR AND SAID TRANSFORMER COMPRISING A FEEDBACK LOOP FOR SAID AMPLIFIER AND ARRANGED TO REDUCE TOWARDS ZERO THE INPUT CURRENT TO SAID AMPLIFIER WHEREBY THE VOLTAGE AT THE OUTPUT TERMINALS OF SAID AMPLIFIER IS RENDERED PROPORTIONAL TO THE VARIABLE VALUE OF THE CAPACITOR IN SAID OTHER ARM OF THE BRIDGE.