The TSI Scanning Mobility Particle Sizer (SMPS) Spectrometer, model 3938, is a high-resolution instrument designed to measure the size distribution of airborne submicrometer and nanoparticles. The system works by size-selecting particles based on their electrical mobility using a Differential Mobility Analyzer (DMA) and then counting the size-selected particles with a Condensation Particle Counter (CPC). By scanning through a range of voltages, it generates a full particle size distribution. The SMPS 3938 series can measure particles in the range from 2.5 nanometers to 1000 nanometers (1 µm), making it a standard tool for nanoparticle characterization in various fields, including atmospheric research, air quality monitoring, nanotechnology research, and combustion studies.