Evaluation of Horiba MEXA 7000 Bag Bench Analyzers for Single Range Operation

Dynamic single range analyzers are designed to cover the wide range of concentrations that once required multiple ranges. The use of single range analyzers is attractive because they can significantly reduce installation costs, gas cylinder charges, and facility storage space. The new technology relies on expansion of the digital dynamic range of the analyzer combined with the availability of a high accuracy gas divider with a 500 to one dilution ratio and a large number of cut points. A series of four MEXA 7000 series bag bench analyzers manufactured by Horiba Instruments, Inc., were evaluated to compare multiple range operation with single range operation. This report describes the operation of these analyzers and summarizes the evaluation methods and results. The evaluation verified the ability of the analyzers to operate in single range mode. The report makes recommendations for the linearization methodologies for each of the four analyzers (THC, NO_X, CO, and CO₂), including the number of cut points, their spacing, and the weighting to be used in the least squares regression. Specific artifacts of the analyzers are characterized and discussed, and remedies are recommended.