Evaluation of Mass Flow Controller Gas Divider For Linearizing Emission Analytical Equipment

The new generation of emission analyzers, MEXA 7000 series, manufactured by Horiba Instruments, Incorporated, operate as single range instruments. The wide operational range of the new analyzers requires a new calibration/linearization tool, a new gas divider capable of providing more calibration points over a wider dynamic operational range. The operation of the new gas divider (Horiba GDC-703), based on mass flow control technology, provides 40 cut points with a minimum step size of 1/500, or 0.2%, of the calibration gas value. This paper describes the new Horiba gas divider, GDC-700 series. The evaluation proves the gas divider's viability for use in engine and vehicle emissions test laboratories. Extensive sets of data were collected to provide an evaluation of the gas divider over a wide range of operation for measurement linearity, repeatability, and accuracy. The major portion of the evaluation was performed using a MEXA-7000 FIA-720 FID analyzer with propane in nitrogen as the calibration gas. The results were then verified on other analyzers using appropriate gases. The gas divider provided calibration gas with residual errors of less than 1.0% of point for most of the analyzers' full operating ranges.