It is desirable to record infrared spectra point by point in digital form on punched cards in order to use automatic-machine methods of processing the data; for example, in calibration, conversion to absorption coefficient, comparison of spectra, subtraction of spectra of an identified constituent from that of an unknown mixture. Recording spectra in this way also allows the introduction of new methods suggested by communication theory of improving signal-to-noise ratio by smoothing noisy data with correlation functions. In applying these methods the computing machine can be considered as a nonlinear filter, part of the infrared equipment.
The punched-card record is made by attaching to the output of the detector voltage amplifier a Digital Reader in parallel with the conventional graphic recorder. The Digital Reader converts the deflection voltage into a binary code represented by closure of circuits. These may be made to operate a Key Punch which punches into a single column of a standard card the record of the voltage in binary digital form. The data can then be processed by standard punched-card equipment.
Examples of various kinds of spectra recorded in digital form on punched cards are presented, together with some examples of processed data.
© 1954 Optical Society of AmericaFull Article | PDF Article
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