Aerosol Messgeraete
Berner Impaktoren
The Berner low pressure impactor was
designed to provide sufficient sample for gravimetric determinations of
aerosol mass distributions, and for chemical analyses requiring sample
extraction. There are several models, with flow rates from 2l/min to 150
l/min.
The most commonly used models are LPI 30/0,06 and LPI 25/0,018 which are
multijet impactors with a flow rate of 30 l/min (25 l/min respectivly),
as measured at the inlet temperature and pressure.
Except for the first stage (as an example for the model LPI 30/0,06),
the impactor has between 7 and 130 equal-diameter jets per stage. The
jets are arranged in a circle. The collection plate has a large hole in
the center for the air to pass to the subsequent stage.
This flow arrangement gives a symetrical flow pattern, and thus deposits
under each jet. The final flow rate through the impactor is controlled
by a critical orifice downstream of the final collection stage.