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The on-going regulatory emphasis on reducing vehicle emission levels and increasing fuel economy has resulting in numerous efforts to improve the technology used to obtain these measurements. For example, raw exhaust flow meters are being implemented to provide improved tailpipe (i.e. modal) emission measurements as part of the vehicle development process. In addition, new sampling system technologies (e.g. partial flow dilution systems) are being implemented that use either synthetic air or catalyzed/dried ambient air to dilute exhaust samples. With these new technologies, however, often comes an increased sensitivity to leakage from both the test equipment and from the hoses/connectors used to route the vehicle's exhaust gas to the test equipment. In the case of the exhaust flow meter, a leak upstream of the measurement zone will provide an inaccurate flow reading. With an emissions sampling system, an exhaust leak will result in inaccurate emissions and fuel economy readings.

Exhaust flow measurements are becoming increasingly important to ensure accurate emissions measurement on both a continuous and averaged (i.e. bag) basis. When performing continuous mass measurements of hydrocarbons, nitrous oxide, carbon monoxide, carbon dioxide and other pollutant/greenhouse gases, the exhaust flow measurement is critical to the task of providing an accurate result. In addition, the acceptance of the Bag Mini-Diluter (BMD) for low-level emissions measurements has amplified the need for an accurate exhaust flow measurement. With the BMD, there is a direct correlation between fuel economy/emissions accuracy and exhaust flow measurement accuracy. To meet these demands, several new exhaust meters have emerged in the last few years that encompass promising technology and unique solutions to the traditional problems that tend to complicate exhaust flow measurements.