Performance of PMS model LAS-X optical particle counter.
J Aerosol Sci 1986 Jan; 17(1):67-72
The performance characteristics of an optical particle counter were evaluated. The effects of particle refractive index (RI) and coincidence errors on particle sizes measured by a Particle Measuring Systems (PMS) model LAS-X optical particle counter were evaluated. The effect of inlet losses on sampling efficiency were also determined. The effect of particle RI was examined by calculating response curves (plots of the counter's signals versus particle diameter) for 170 particle diameters covering the range 0.05 to 37.8 micrometers (microm) for 32 RIs using 11 different substances and comparing these with actual measurements. For nonabsorbing particles, positive errors (oversizing) were greater than negative errors (undersizing). The presence of absorbing particles greatly increased the magnitude of potential undersizing errors. All RI groups showed a potential for significant oversizing errors when the particle sizes exceeded 3.0microm. The response of the PMS counter against that of a single stage impactor was checked using aerosols of oleic-acid, RI 1.4582, having particle diameters of 0.3 to 7.5microm. The sizes indicated by the PMS counter agreed well with those registered by the impactor except for some unexplained differences in the vicinity of 1microm. The effect of coincidence was evaluated using aerosols of dioctyl-phthalate at various concentrations and measuring the effect on the CMD. For aerosol concentrations below 10(-4) particles per cubic centimeter (cc), the errors in the CMD were less than 10%. The effects of inlet losses on sampling efficiency were assessed using monodisperse methylene-blue aerosols having aerodynamic diameters of 1.8 to 12.5microm at sample flow rates of 1 to 50cc per second. Inlet losses increased with increasing particle size and flow rate. A 50% loss of 12.5microm diameter particles occurred at a flow rate of 5cc/second.
NIOSH-Publication; NIOSH-Grant; Respirators; Aerosol-particles; Analytical-instruments; Aerosol-sampling; Equipment-reliability; Laboratory-testing
Environ and Nutritional Scis University of California 405 Hilgard Avenue Los Angeles, Calif 90024
Journal of Aerosol Science
University of California Los Angeles, Los Angeles, California