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The goal of the present work was to investigate the ability of the SEMTECH®-D Portable Emissions Measurement System (PEMS) to provide simultaneous, accurate, real-time (1Hz) measurements of NO and NO2 in vehicle exhaust. Extensive chassis dynamometer laboratory evaluation studies of the SEMTECH® system were conducted. The instantaneous (1Hz) NOx emissions were measured using a conventional chemiluminescence analyzer (CLA) and were compared to the sum of the instantaneous NO and NO2 measurements from the SEMTECH®-D. The sum of the NO and NO2 emissions measured by the SEMTECH® were in excellent agreement (within 95% in most cases) with the total NOx measurements from the conventional CLA. During the laboratory evaluation studies, several Federal Test Procedure (FTP) drive cycles were conducted. Examples of the NO and NO2 concentration and mass emissions measured using the SEMTECH®-D are presented along with the corresponding SEMTECH®-D detection limits.

A commercially available Portable Emissions Measurement System (PEMS), the SEMTECH-G® (Sensors Inc., Saline, MI), was evaluated under laboratory conditions at a chassis dynamometer test facility at Ford Motor Company's Research and Innovation Center. Cumulative Mass Emissions (CMEs) for carbon monoxide (CO), total hydrocarbons (THC), oxides of nitrogen (NOx), and carbon dioxide (CO2) were measured for three different gasoline powered vehicles. A total of twenty three test cycles were conducted. Results from the conventional laboratory bag analyzer system (Horiba MEXA®7200-TR), the conventional laboratory modal analyzer system (Horiba MEXA® 7100-DEGR), and SEMTECH-G® were compared. CMEs for CO, THC, NOx, and CO2 measured using the SEMTECH-G® were found to be in good agreement (within 10% in all cases) with the results from the conventional modal analyzers.