Filter stage

ELPI™ filter stage extends the standard ELPI™ measurement range from 30 nm – 10 µm to 7 nm – 10 µm. The filter stage is a back-up filter installed under the impactor stages; stage 12 is removed from the impactor assembly to enable an easy upgrade and use of the existing electrometers. The upgrade is fully reversible; the ELPI™ can be used with or without the filter stage after the upgrade.

The impactor flow control works the same way whether or not the filter stage is used; the flow is kept constant by adjusting 100 mbar under the impactor stage #1. When the filter stage is used, measurement of pressure above the filter stage requires minor changes to the ELPI™ configuration, which are automatically taken into account in the ELPIVI software.

Different types of filters can be used on the filter stage to collect the particles. The filters used on the filter stage are 47 mm in diameter and the requirements for the filter material are; good collection efficiency for particles < 30 nm and low flow resistance so that the 100 mbar pressure is still achieved above the filter with the pump. Suitable filters are available at Dekati, and recommendations for suitable filter-pump combinations can be requested from support@dekati.fi.

More information on the ELPI™ filter stage:

Marjamäki, M., Ntziachristos, L., Virtanen, A., Ristimäki, J. Keskinen, J., Moisio, M., Palonen, M. & Lappi, M. 2002. Electrical Filter Stage for the ELPI. SAE Technical Paper series 2002-01-0055.