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Scanning Mobility Particle Sizer Spectrometer 3938

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Product Details

TSI's newest Scanning Mobility Particle Sizer SMPS™ spectrometer is widely used as the standard for measuring airborne particle size distributions. This system is also routinely used to make accurate nanoparticle size measurements of particles suspended in liquids. The National Institute of Standards and Technology (NIST) uses a TSI DMA to size 60 nm and 100 nm standard size reference materials. SMPS spectrometer sizing is a discreet technique in which number concentrations are measured directly without assuming the shape of the particle size distribution. The method is independent of the refractive index of the particle or fluid, and has a high degree of absolute sizing accuracy and measurement repeatability. TSI's Model 3938 is the 3rd generation of SMPS, trusted by researchers for over 30 years.

Features and Benefits

  • High resolution data: up to 167 channels
  • Broad size range: from 1 nm to 1,000 nm
  • ISO 15900:2009 compliant
  • Fast measurements: <10 second scans
  • Wide concentration range up 10 7 particles/cm 3
  • Component design for maximum flexibility
  • Touch-screen control with no computer needed for operation
  • Easy setup with tool-less installation and auto discovery of components 
  • Discreet particle measurement: works well for multi-mode samples
  • Independent of optical properties of the particles and fluid
  • Wide range of system options: choice of water or butanol CPC; choice of traditional or nonradioactive neutralizer


  •  Nanotechnology research and materials synthesis 
  •  Atmospheric studies and environmental monitoring 
  •  Combustion and engine exhaust studies 
  •  Indoor air quality measurements 
  •  Nucleation/condensation studies 
  •  Inhalation toxicology studies 

Included Items

  • Electrostatic Classifier with your choice of DMA column
  • One of seven CPCs
  • Aerosol Instrument Manager® software

Computers for data collection must be purchased separately.

Resource Center

  • Can the SMPS spectrometer measure aerosols at different temperatures and pressures?
    Temperature and pressure affect the mean-free-path in air which will affect the electrical mobility of the particles. Charging of the aerosol will also be effected. The effects of pressure and temperature deviating from standard conditions have not been characterized; however, the sample temperature and pressure measured by the SMPS spectrometer are used in electrical mobility and charging calculations
  • Can the SMPS spectrometer measure particles in a gaseous medium other than air?
    The SMPS program has built in gas and charging parameters for air (or nitrogen) but physical properties of other carrier gases such as temperature, pressure, mean free path, and gas viscosity can be manually entered and used for calculations.
  • Do I need a 10-to-1 flow ratio between the aerosol flow and the sheath air flow?
    The SMPS software allows for flow ratios other than 10 to 1. For most applications, the recommended flow ratio is 10 to 1. High flow ratios will give better size resolution but lower the particle count statistics. This may be useful when measuring the exact size of monodisperse aerosols. Lower flow ratios will improve the counting statistics, but decrease the effective size resolution. This is useful for filter testing when measuring downstream of a high-efficiency filter. Flow ratios that differ too much from 10 to 1 may cause turbulence in the DMA and degrade the sizing resolution.
  • Does the SMPS software collect particle concentration data on both the up and down voltage scans?
    The SMPS spectrometer Model 3938 has implemented an instantaneous down scan; therefore only up scan data are used.
  • How is the charge distribution determined?
    The SMPS software uses tables of charge probabilities named Charge***.dat, where *** represents the type of aerosol neutralizer (soft x-ray, or krypton) and the particle polarity (positive or negative) used. The tables contain 162 particle size channels with charge probabilities up to 10 positive charges and were generated based on the work of Alfred Wiedensohler1.References 1. Wiedensohler, A., 1988, "An Approximation of the Bipolar Charge Distribution for Particles in the Submicron Size Range," Journal of Aerosol Science, 19(1): 387–389 
  • How is the SMPS spectrometer calibrated?
    Complete SMPS spectrometer systems purchased from TSI are set up and compared to standard instruments at TSI to verify correct operation. The CPC, Electrostatic Classifier, and impactor are components of the SMPS spectrometer system and are calibrated independently.

Required Components

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