Method for obtaining improved output signals from a dual beam spectrometer

Abstract

Abstract THIS INVENTION RELATES TO METHOD AND MEANS FOR OBTAINING AN IMPROVED OUTPUT SIGNAL FROM A DUAL BEAM ELECTRICAL RATIONING INFRARED SPECTROMETER. THE OUTPUT SIGNAL IS OBTAINED BY COMPARING THE SAMPLE BEAM SIGNAL (MEASURING BEAM) TO THE REFERENCE BEAM SIGNAL STANDARD BEAM). THE SPECTROMETER USES A SINGLE RADIATION SOURCE. THE SOURCE BEAM IS ALTERNATIVELY DIRECTED AT 15 HERTZ RATE THROUGH THE REFERENCE AND HE SAMPLE PATHS OF THE INSTRUMENT. THE SOURCE BEAMS ARE RECOMBINED AND FORM A SINGLE OUTPUT SIGNAL FROM THE DETECTOR. THE OUTPUT SIGNAL IS AMPLIFIED AND SEPARATED INTO ITS TWO COMPONENTS BY A SYNCHRONOUS RECTIFIER. THE TWO SIGNALS ARE COMPARED TO OBTAIN THE RATIO OF SAMPLE TO REFERENCE SIGNAL STRENGTH, WHICH IS A MEASURE OF ENERGY ABSORPTION IN THE SAMPLE. SINCE THE TWO ENERGY BEAMS ARE ALTERNATE 15 HERTZ HALF CYCLES, THE OUTPUT SIGNAL OF EACH IS DISPLACED IN TIME BY 1/30 SEC. AND CANNOT BE DIRECTLY COMPARED. EACH TIME SEPARATED SIGNAL IS CONNECTED TO A PARALLEL RESONANT TUNED TRANSFORMER. THE WINDINGS ARE TURNED TO 15 HERTZ AND HAVE A HIGH Q. THE Q FACTOR IS A QUALITY OF THE RESONANT CIRCUIT, Q=WL/R, AND DETERMINES THE FREQUENCY BANDWIDTH AND THE DECAY TIME CONSTANT OF THE CIRCUIT. SINCE THE OUTPUT SIGNAL FREQUENCY IS ONLY 15 HERTZ, THE TWO SIGNALS CAN BE DIRECTLY COMPARED BY PHASE INVERSION OF ONE OF THE SIGNALS.

Inventors

• 👤 Franklin J Karle

Bibliographic Details