Performance of PMS model LAS-X optical particle counter

Abstract Performance characteristics of a Particle Measuring System (PMS) Model LAS-X (0.12–7.5 μm) optical particle counter were evaluated. The effect of particle refractive index was determined theoretically by calculating response curves for 32 refractive indexes. Nonabsorbing organic particles with unknown refractive index have measurement errors that range from −50 to +20%. Unknown particles (including absorbing particles) may have measurement errors from −60 to +250%. An aerodynamic calibration of range 3 (0.12–7.5 μm) with oleic acid particles found the indicated sizes to be within ±2 channel widths of the correct aerodynamic diameters. Measurements of the effect of coincidence on measured size found errors in CMD to be less than 10% for concentrations below 10,000 cm −3 . Experimental measurements of inlet losses showed a dependence on particle size and sample flow rate with about 50% loss of 12 μm particles at a sampling rate of 5 cm 3 s −1 .