Performance of a New Commercial Electrical Mobility Spectrometer

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Abstract
A commercial electrical mobility spectrometer (Grimm 5.4-900 DMA and Grimm 5.403 CPC) was examined with respect to size, concentration and time-dependent responses of the CPC, the transfer function of the DMA, as well as the performance of the data inversion algorithm. For comparison with previously published results, the responses were also measured for two other commercial CPCs (TSI Model 3010 and TSI Model 3022). All measurements were performed using sodium chloride aerosol produced by an atomizer, except for size-dependent counting efficiency measurements, where an evaporation and condensation method was used to produce particles down to a size of 2 nm. The concentration-dependent CPC counting efficiency was measured against a reference instrument working in the single particle count mode following dilution. The CPC time response was evaluated for monodisperse aerosol by measuring the step response using a solenoid valve technique. The transfer function of the Grimm DMA 5.4-900 was determined between 10 and 100 nm with two verified identical DMAs in series following the approach of Fissan et al. Measured tandem-DMA responses were compared to simulated responses based on the diffusion-broadened transfer function of Stolzenburg to define the factors influencing resolution. Finally the data inversion algorithm was tested by comparison with other devices.