Characteristics of an aerosol photometer while automatically controlling chamber dilution-air flow rate.
Inhal Toxicol 2000 Oct; 12(10):979-996
Trials were conducted to determine those factors that affect the accuracy of a direct-reading aerosol photometer when automatically controlling airflow rate within an exposure chamber to regulate airborne dust concentrations. Photometer response was affected by a shift in the aerosol size distribution caused by changes in chamber flow rate. In addition to a dilution effect, flow rate also determined the relative amount of aerosol lost to sedimentation within the chamber. Additional calculations were added to a computer control algorithm to compensate for these effects when attempting to automatically regulate flow based on a proportional-integral-derivative (PID) feedback control algorithm. A comparison between PID-controlled trials and those performed with a constant generator output rate and dilution-air flow rate demonstrated that there was no significant decrease in photometer accuracy despite the many changes in flow rate produced when using PID control. Likewise, the PID-controlled trials produced chamber aerosol concentrations within 1% of a desired level.
Aerosol-particles; Airborne-dusts; Dust-exposure; Equipment-design; Exposure-levels; Automation; Exposure-chambers; Aerosol-particles; Aerosol-sampling; Mathematical-models
Department of Occupational and Environmental Health, University of Iowa, 100 Oakdale Campus, #180 IREH, Iowa City, IA 52242-5000
University of Vermont & St Agric College, Burlington, Vermont