The PM2 analyzer utilizes an ejector dilution system. HEPA filtered dilution air flows into the diluter and is directed around the ejector nozzle at a high velocity. This causes a pressure drop which draws in the sample through the nozzle. The raw sample mixes with the dilution air resulting in a stable homogeneous diluted sample.
For real-time PM mass measurement, a small fraction of the homogenous diluted sample is passed through a Pegasor PPS-M electrical aerosol transducer, in which particulate matter is charged. As the charged particles exit the detection zone, their charge is measured with a sensitive electrometer. The electrometer signal is then converted to real-time PM mass concentration using a transfer function.
For cumulative PM mass measurement, the homogeneous diluted sample is directed through one of three filters. The pre- and post- filter weights provide cumulative PM mass, which is used to scale the real-time mass concentration and obtain accurate, time resolved PM mass measurement.