What is the correlation between gravimetric measurement and DMM obtained data?
DMM result is usually within 10% when compared to gravimetric measurement. Sampling system and presence of volatile/semi-volatile particles might increase the difference (see next 2 questions). 8. After DPF the DMM shows almost zero result while the gravimetric measurement shows much higher emission. A typical filter paper collects particles with high efficiency, but they also adsorb gas-phase volatile material (e.g. hydrocarbons). DMM does not measure any gas-phase material. With conventional diesel engines this filter artefact is almost negligible, but after DPF most of the solid particles are removed and filter artefact becomes more significant. See article SAE2004-01-0967 for more information.
