Weighing scale with removed material indicator

Claim 1

A WEIGHING SCALE FOR INDICATING, AS A POSITIVE VALUE, THE WEIGHT OF MATERIAL REMOVED FROM A BASE WEIGHT OF MATERIAL ON THE SCALE COMPRISING: A TRANSDUCER FOR GENERATING A VOLTAGE WHOSE AMPLITUDE IS PROPORTIONAL TO THE INSTANTANEOUS WEIGHT OF MATERIAL ON THE SCALE, A FIRST VOLTAGE CIRCUIT FOR GENERATING A VOLTAGE IN PHASE OPPOSITION TO SAID TRANSDUCER OUTPUT VOLTAGE, SAID FIRST VOLTAGE CIRCUIT INCLUDING FIRST ADJUSTABLE MEANS SETTABLE FOR ESTABLISHING THE AMPLITUDE OF SAID FIRST VOLTAGE CIRCUIT TO AN AMOUNT EQUAL TO THE AMPLITUDE OF SAID TRANSDUCER OUTPUT VOLTAGE REPRESENTATIVE OF TARE WEIGHT AND SECOND ADJUSTABLE MEANS SETTABLE FOR ESTABLISHING THE AMPLITUDE OF SAID FIRST VOLTAGE CIRCUIT TO AN AMOUNT EQUAL TO THE AMPLITUDE OF SAID TRANSDUCER OUTPUT VOLTAGE REPRESENTATIVE OF THE BASE WEIGHT OF MATERIAL ON THE SCALE, A SECOND VOLTAGE CIRCUIT CONNECTABLE IN SERIES WITH SAID TRANSDUCER AND SAID FIRST VOLTAGE CIRCUIT FOR GENERATING A VOLTAGE HAVING A SELECTABLE PHASE RELATION WITH THE OUTPUT VOLTAGE OF SAID TRANSDUCER, MEANS FOR SELECTING THE VOLTAGE PHASE RELATION OF SAID SECOND VOLTAGE CIRCUIT RELATIVE TO THE TRANSDUCER COMPRISING REVERSING SWITCH MEANS POSITIONABLE SELECTIVELY TO CONNECT THE SECOND VOLTAGE CIRCUIT WITH SAID FIRST VOLTAGE CIRCUIT THROUGH ONE OF SAID FIRST AND SECOND ADJUSTABLE MEANS, AMPLIFIER AND BALANCE DETECTOR MEANS IN SERIES CIRCUIT WITH SAID TRANSDUCER, SAID FIRST VOLTAGE MEANS AND SAID SECOND VOLTAGE MEANS FOR SENSING A CONDITION OF ZERO VOLTAGE IN SAID SERIES CIRCUIT, SERVOMOTOR MEANS OPERATIVELY CONNECTED TO SAID TRANSDUCER, SAID FIRST AND SAID SECOND VOLTAGE CIRCUITS, SAID SERVOMOTOR MEANS BEING FURTHER CONNECTED TO SAID SECOND VOLTAGE MEANS TO ADJUST THE AMPLITUDE OF SAID VOLTAGE OF SAID SECOND VOLTAGE CIRCUIT TO AN AMOUNT EQUAL TO THE DIFFERENCE BETWEEN THE OUTPUT VOLTAGE OF SAID TRANSDUCER AND THE OUTPUT VOLTAGE OF SAID FIRST VOLTAGE CIRCUIT, PRINTING MEANS HAVING SENSED ELEMENTS SETTABLE BY SAID SERVOMOTOR AND HAVING PRINTING MEMBERS TO PRODUCE A PRINTED RECORD OF THE AMOUNT OF MATERIAL REMOVED FROM THE SCALE, AND CONTACT MEANS CONTROLLED BY SAID BALANCE DETECTOR TO PREVENT OPERATION OF SAID PRINTING MEANS UNTIL SAID ZERO VOLTAGE CONDITION PREVAILS.