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    Definition, Functional Design, and Implementation of a Dedicated Computerized Laboratory System: The GC Computing Recorder

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    This paper describes the process employed in defining and creating an integrated instrument with computing and recording capability that generates a document containing a full chromatogram juxtaposed with its quantitative on-line analysis. This selfcontained system, called the GC Computing Recorder, operates from the raw gas chromatograph detector signal through appropriate signal conditioning, analog-to-digital conversion, microcomputer-based digital integration and postintegration calculation to generate the final analytical report, termed the integrated chromatogram.

    The paper briefly reviews the historical development of gas chromatographic quantitation technology and it postulates the system requirements for single channel quantitation instrumentation. Then, it summarizes the specific design approaches considered for the computing recorder, the evolution of the system architecture from the point of view of its inputs and outputs, and the selection of the architectural approach adopted for the final design. Particular attention is devoted to man/machine interface considerations, signal conditioning design, digital filtering, analog-to-digital conversion techniques, and firmware integration treatments.

    Criteria developed to enhance the integration portion of the system firmware are explored, and the algorithmic treatments of overlapping peaks, drifting baselines, area recovery, and multiple peak resolution are discussed. The detailed systems description also covers the areas of postintegration calculations including area normalization, response factors, and relative retention times, as well as the application of internal standard methods for precision determinations of component concentration levels.

    Experience with the instrument under actual laboratory conditions is summarized, and observations are made concerning possible system extensions.


    computers, laboratories, recording instruments, computing, microcomputers, chromatogram, gas chromatography, measure and integration, firmware, detectors, signal processing, algorithms, normalizing (statistics), response factors, retention times, digital filters, analog to digital converters, concentration, quantitative analysis, internal standard, peak resolution

    Author Information:

    Zawadowicz, ST
    Market manager and senior design engineer, Process Control Division/Fort Washington, Honeywell Inc., Fort Washington, Pa.

    Kegg, AL
    Market manager and senior design engineer, Process Control Division/Fort Washington, Honeywell Inc., Fort Washington, Pa.

    Committee/Subcommittee: E31.40

    DOI: 10.1520/STP33345S