Conceptual possibilities for extending the particle size range of a differential mobility analyzer using longitudinal and transversal electrodes

A new type of differential mobility analyzer (DMA) is proposed which is, in theory, applicable to the measurement of particle size distributions of aerosols over the full range of particle size. The basic concept of the full-range DMA can be best realized using a parallel-plate geometry. It contains two arrays of detectors, e.g. thin metal strips connected to electrometers. One array of detectors is placed longitudinally along one of the plates, and the other one is placed transversally downstream of the aerosol entrance. With this arrangement, too low mobility particles which escape undetected in a conventional DMA settle onto the transversal detectors and can thus be measured. For small particles collected along the longitudinal array of detectors, the resolution of the instrument is the same as for a conventional multi-channel DMA. For the largest particles, which are collected on the transversal detectors, the resolution deteriorates as the particle size increases.