Experimental Methods for Reducing Uncertainty of Measurement on Vehicle Emission Testing 2004-01-1961
Uncertainty in measurements is a complex issue in the process of obtaining accurate results in a vehicle emission test. Based on the ISO GUM (Guide to the expression of uncertainty in measurement), a study was carried out to calculate the final uncertainty of measurement during a vehicle emission test following a feasible method that can be used in many laboratories. When applying the methods in other laboratories high uncertainty values may be obtained for some pollutants making the compliance with emission requirements a difficult task to attain.
To reduce expanded uncertainty of measurement, it is necessary to estimate and reduce the influence of several variables on the final result, including type B (calibration certificates, reference materials, transducers and sensors, calculations) and type A (repeatability) uncertainty budgets.
This paper describes the steps followed in some experimental methods for reducing the uncertainty in measurements in light duty vehicle emission tests, including gas pollutants (CO, NOX, HC and CO2) and aldehydes, both in g/km (grams/kilometer). This paper also provides an overview of Brazilian emission legislation and some procedures for vehicle emission testing.