Laboratory Evaluation of the SEMTECH-G® Portable Emissions Measurement System (PEMS) For Gasoline Fueled Vehicles

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. The CMEs measured using the PEMS and the conventional modal analyzers were also found to be in good agreement (within 7% or better) with the results from the Horiba bag analyzers for CO, CO₂, and THC. Interestingly, the NOx CMEs measured using the PEMS and the conventional modal analyzer were in very good agreement with each other, but were low (by approximately 16%) relative to the results from the bag analyzer. Approximately half of NOx CMEs measured were less than 0.1 gram/mile. The disagreement between the modal and bag analyzer results might arise from the fact that both the PEMS and the conventional modal NOx analyzers are often measuring at, or below, their detection limits during a good portion of these tests. The results of this study suggest that the SEMTECH-G^® is capable of measuring emissions from standard gasoline powered vehicles typical of the current on-road fleet to an accuracy approaching that of conventional laboratory modal analyzer systems.