Cancellation circuit for non-dispersive infrared analyzer

Claim 1

IN AN INFRARED ANALYZER, A RADIANT ENERGY SOURCE, FIRST MEANS FOR ENERGIZING SAID SOURCE, A SAMPLE CELL AND AT LEAST A FIRST DETECTOR CELL MOUNTED IN OPTICAL SERIES FOR RADIATION FROM SAID SOURCE, SAID DETECTOR CELL INCLUDING A CAPACITIVE TRANSDUCER, A BIAS VOLTAGE SOURCE CONNECTED WITH SAID TRANSDUCER, SAID TRANSDUCER PROVIDING AN OUTPUT SIGNAL WHICH IS A FUNCTION OF ENERGY CHANGES WITHIN SAID DETECTOR CELL, MEANS COUPLING THE OUTPUT OF SAID TRANSDUCER TO AN AMPLIFYING MEANS AND MEANS COUPLING THE OUTPUT OF SAID AMPLIFYING MEANS TO A DEMODULATOR MEANS, A FEEDBACK CIRCUIT COUPLED FROM SAID DEMODULATOR MEANS TO SAID BIAS VOLTAGE SOURCE, SAID TRANSDUCER COUPLING UNWANTED A.C. SIGNALS TO THE INPUT OF SAID AMPLIFYING MEANS FROM SAID DEMODULATOR MEANS, THE IMPROVEMENT COMPRISING A PASSIVE A.C. CIRCUIT COUPLED FROM THE OUTPUT OF SAID DEMODULATOR MEANS TO SAID AMPLIFYING MEANS TO COUPLE A.C. SIGNALS OF A PROPER PHASE AND MAGNITUDE TO SAID AMPLIFYING MEANS WHEREBY THE OUTPUT OF SAID AMPLIFYING MEANS IS SUBSTANTIALLY DEVOID OF ANY UNWATED A.C. SIGNALS.