DYCOMS-II: C-130 Aerosol LAS-AIR Optical Particle Counter

The LAS-AIR is a commercial instrument (PMS Model 1001) that measured the size distribution of particles between about 0.1 to > 3 microns diameter in 8 size channels. During DYCOMS, the LAS-AIR was one of a number of instruments sampling off the solid diffuser inlet (SDI) which was mounted on the right side of the C-130 aircraft. To dry the sample and prevent coincidence at high concentrations, the LAS-AIR sample stream was diluted with dry nitrogen in a 5:1 ratio (5 parts N2 to 1 part sample). All flow rates were monitored and maintained with constant volume flow controllers. The LAS-AIR samples over a 6 sec interval, so the data rate is once every 6 seconds. Rather than using the manufacturer's calibration, size limits were calibrated using monodisperse ammonium sulfate aerosol. Additional information on the LAS-AIR itself can be found on the PMS website at http://www.pmeasuring.com/particle/products/aerosol/docs/lasair