EXPERIMENTAL COMPARISON OF 4 DIFFERENTIAL MOBILITY ANALYZERS FOR NANOMETER AEROSOL MEASUREMENTS

The performance of four differential mobility analyzers (DMAs), namely the TSI-long, the TSI-short, the Hauke 3/150, and the Spectrometre de Mobilite Electrique Circulaire (SMEC) were evaluated under the same c onditions of flow rates, how ratio, input monodisperse aerosols, and t ransport-line lengths. The evaluations were performed under the condit ions of 10 l/min sheath air and 1 l/min aerosol flow rates, and at a f low ratio of 10:1. Monodisperse aerosols in the size range of 6 nm to 50 nm were obtained by classifying condensation aerosols using a Hauke DMA operated at 20:1 flow ratio. The transfer functions of all four D MAs have been obtained by deconvoluting the scan results of the evalua ted DMA (DMA2), and by using the empirical transfer function of the fi rst DMA (DMA1, the Hauke DMA at 20:10 flow ratio). The half-width, hei ght, and area of the transfer functions have been compared for the fou r DMAs tested. These results provide a quantitative comparison of the mobility resolution and diffusion loss of the nanometer aerosols in th e DMAs.