Previous research of a proper margin value for Nitrogen Oxides to account for the additional measurement uncertainty of Portable Emissions Measurement Systems (PEMS) as compared to standard laboratory equipment in the context of the Real Driving Emissions (RDE) Regulation identified zero drift as an important component of uncertainty.
This report describes an experimental campaign carried out by the Joint Research Centre during 2018 and 2019 to assess zero drift of PEMS gas analysers under real life operation. The instruments considered in the analysis, from four large manufacturers, cover probably the whole PEMS market in Europe. The tested instruments belong to the generation of PEMS currently available in the market.
The results of the testing campaign show that there is not a systematic positive or negative drift, neither a systematic step nor linear drift for any of the pollutants considered (NO, NO2, CO2, CO). On valid tests, intermediate zero response checks done every 10/20 minutes of test are always within the permissible limits (on HORIBA, SENSORS, and AIP PEMS), and mostly within limits for AVL PEMS (larger number of tests performed with this instrument). On most of the tests performed, the zero drift for NOx is lower than 3 ppm under a variety of ambient temperature and humidity conditions. Additional tests done on more stringent environmental conditions (high altitude mountain driving) show a similar pattern for zero drifts of all pollutants. Vehicle technology (spark ignition or compression ignition), PEMS installation location (cabin or trailer hook), ambient temperature and humidity, and altitude do not appear to be critical elements affecting the zero drift as results are similar for all the aforementioned conditions.
In general, the evidence gathered during the campaign does not verify the worst case drift scenario used to define the 0.43 NOX margin and it can be used to justify a further reduction of the margin value. Based on the worst case scenario for zero drift of the JRC testing campaign and considering the effect on a vehicle with large engine displacement (largest effect in terms of NOx mass), the updated NOx margin that is proposed is 0.32.
VALVERDE MORALES Victor;
GIECHASKIEL Barouch;
CARRIERO Massimo;
2020-02-18
Publications Office of the European Union
JRC114416
978-92-76-16365-7 (online),
978-92-76-16364-0 (print),
1831-9424 (online),
1018-5593 (print),
EUR 30099 EN,
OP KJ-NA-30099-EN-N (online),
OP KJ-NA-30099-EN-C (print),
https://publications.jrc.ec.europa.eu/repository/handle/JRC114416,
10.2760/06282 (online),
10.2760/684820 (print),
