Control apparatus

Claim 1

LIQUID LEVEL MEASURING APPARATUS COMPRISING, IN COMBINATION: CAPACITIVE TANK UNIT MEANS FOR INSERTION IN A CONTAINER OF A LIQUID THE QUANTITY OF WHICH IS TO BE MEASURED; OSCILLATOR MEANS HAVING INPUT MEANS AND FIRST, SECOND AND THIRD OUTPUT MEANS, SAID FIRST AND SECOND OUTPUT MEANS SUPPLYING FIRST AND SECOND OPPOSITE PHASE OUTPUT SIGNALS TO BE USED RESPECTIVE FOR POSITIVE AND NEGATIVE FEEDBACK AROUND SAID OSCILLATOR MEANS; MEANS CONNECTING SAID TANK UNIT BETWEEN SAID FIRST OUTPUT MEANS AND SAID INPUT MEANS OF SAID OSCILLATOR MEANS, THE AMPLITUDE OF THE POSITIVE FEEDBACK SIGNAL BEING DEPENDENT UPON THE QUANTITY OF LIQUID BETWEEN THE ELECTRODES OF SAID TANK UNIT MEANS; VARIABLE FEEDBACK MEANS CONNECTED BETWEEN SAID SECOND OUTPUT MEANS AND SAID INPUT MEANS OF SAID OSCILLATOR MEANS FOR SUPPLYING A NEGATIVE FEEDBACK SIGNAL THERETO, SAID VARIABLE FEEDBACK MEANS INCLUDING INPUT MEANS FOR VARYING THE AMPLITUDE OF SAID NEGATIVE FEEDBACK SIGNAL; DEMODULATOR MEANS, INCLUDING OUTPUT MEANS, CONNECTED TO SAID THIRD OUTPUT MEANS OF SAID OSCILLATOR MEANS FOR RECEIVING A THIRD OUPUT SIGNAL THEREFROM, AND DEMODULATOR MEANS PROVIDING A FOURTH OUTPUT SIGNAL AT SAID OUTPUT MEANS OF SAID DEMODULATOR MEANS WHICH IS AMPLITUDE DEPENDENT UPON THE SIGNAL RECEIVED FROM SAID OSCILLATOR MEANS; REFERENCE SIGNAL SUPPLYING MEANS FOR SUPPLYING A REFERENCE SIGNAL; MOTIVE MEAN, INCLUDING MECHANICAL OUTPUT MEANS, CONNECTED BETWEEN SAID VOLTAGE REFERENCE MEANS AND SAID OUTPUT MEANS OF SAID DEMODULATOR MEANS, SAID MOTIVE MEANS SUPPLYING AN OUTPUT AT SAID MECHANICAL OUTPUT MEANS WHEN MORE THAN A PREDETERMINED VOLTAGE DIFFERENTIAL OCCURS BETWEEN SAID FOURTH OUTPUT SIGNAL AND SAID REFERENCE SIGNAL; INDICATOR MEANS FOR PROVIDING AN OUTPUT INDICATIVE OF LIQUID LEVEL; AND MEANS CONNECTING SAID MECHANICAL OUPUT MEANS OF SAID MOTIVE MEANS TO SAID INDICATOR MEANS FOR PROVIDING AN OUTPUT INDICATION AND TO SAID INPUT MEANS OF SAID VARIABLE FEEDBACK MEANS TO ALTER THE AMPLITUDE OF OSCILLATION OF SAID OSCILLATOR MEANS TOWARD A PREDETERMINED LEVEL BY VARYING THE NEGATIVE FEEDBACK SIGNAL.