Scanning Electrical Mobility Spectrometer (SEMS)

Model 2100


The SEMS is a scanning mobility spectrometer that allows rapid aerosol number size distribution measurements. Scan times of just a few seconds are possible. It also serves as a monodisperse particle generator to calibrate other particle instruments. The SEMS is an easy-to-use and field-ready tool. With an intuitive software interface, the SEMS is easy to configure with quick data post-processing capabilities. Plotting and analysis tools allow you to plot and analyze your data during acquisition. With the broadest size range commercially available, the SEMS can satisfy more scientific needs and adapt to changing research priorities.

  • Broadest available particle size range – select up to 2 micron diameter
  • Fast MCPC response and DMA scan times down to a few seconds
  • Precise volumetric airflow measurements with laminar flow elements
  • Easy to use software with real-time display of Number, Area and Volume distributions and timelines of all integrated properties
  • Integrated sample/sheath flow drying for low RH operation
  • Low maximum voltage (< 5500 volts) reduces arcing problems
  • Real-time temperature, relative humidity and pressure measurements


  • Broad operating pressure range allows use on aircraft – tested to 200 mb
  • Fully automated, unattended operation
  • Monodisperse particle selection and scanning software with on-line inversion
  • Off-line inversion software for data re-processing when needed
  • Configuration, calibration, and characteristic time software utilities

Technical Specs

Scanning Electrical Mobility Spectrometer

parameter value type
Selectable particle diameter size range 0.005—1.0 or 0.01 – 2.0¹ µm
Size resolution (set by Qaer/Qsheath) Variable (28:1 typical)
Scan time range 5 secs to > 1 hour
Sheath flow range 2.5-12 lpm
Aerosol sample flow range 0.1 to 2.0 lpm
Particle concentration range 1-107 cm-3
Range of high voltage 0-5,500 Volts
Pre-impactor cut size diameter 0.5 or 1.0 micron
Communications Ethernet and RS-232
CPC working fluid 1-Butanol
Operating Temperature 15-35°C
Operating Pressure 200-1,000 mb ²
Physical size 19w x 13d x 22h inch
(48w x 33d x 56h cm)
Weight 35 lbs (16 kg)
Power usage 80 watts (85 to 230 VAC)
1. 2 micron sizing with SEMS-DMA2 option.
2. Only with SEMS-ExP options.

Copyright ©2015 All specifications are subject to change without notice. BMI assumes no responsibility for any inaccuracies in this document or for any obligation to update information in this document. BMI reserves the right to change, modify, transfer, or otherwise revise this publication without notice.

Applications and Solutions

  • Continuous monitoring of ambient size distributions
  • Laboratory flow-tube studies
  • Cloud condensation nucleus studies
  • Visibility reduction studies
  • Aerosol health impacts
  • Long-term climate and air quality monitoring
  • Sampling conditions with highly transient aerosol concentrations
  • Vertical profiles of number distributions from aircraft

What’s Included

The SEMS comes with the following items:

  • Differential Mobility Analyzer column (1um or 2um)
  • High voltage supply and control
  • Automatic DMA recirculating airflow control
  • Scanning size distribution software with on-line inversion
  • Monodisperse particle selection software
  • Size distribution off-line inversion software for data re-processing
  • Configuration and Calibration Software Utilities
  • Mixing-based Condensation Particle Counter
  • Instrument enclosure
  • Temperature and Pressure measurement in DMA
  • Operating manual
    (External WindowsTM computer required for scanning operation.)


The SEMS software features a graphical user interface with point-and-click operation. A real-time display of the particle size distribution is available through plots of measured number concentrations versus size as well as diameter bin number. Data are displayed as raw counts, raw concentration or inverted number, area and volume size distributions. The raw count display offers useful guidance on setting scan parameters to optimize counting uncertainties. The current scan, previous scan and a running average of all scans is shown in each results screen. With just a click of the mouse you have immediate access to plots of the number, area and volume distributions in addition to timeline plots of the integrated number, area, volume and even mass concentrations!

Software tools are provided that allow you to easily configure the default settings of instrument parameters like scan times and scan size range, as well as to determine the plumbing delay time for accurate DMA sizing. Just in case you happen to operate the SEMS with an incorrect setting, we provide an off-line software inversion tool that lets you re-process raw scan data with the correct setting values.


The following optional accessories are available:

SEMS accessories list

Part Number Description
8008 Particle Round Jet Impactor (0.5 µm cut size, 0.7 lpm flow)
8009 Particle Round Jet Impactor (1.0 µm cut size, 0.7 lpm flow)
9000 Aerosol charge neutralizer (requires Polonium-210 radioactive sources)
9001 Aerosol non-radioactive charger (available 2017)
9002 Aerosol Soft X-ray charger
9200 Aerosol Generation System
SEMS-DMA2 Large particle (2µm) sizing package
SEMS-DrySize Dry sizing package
SEMS-ExP115 External vacuum pump, 115V
SEMS-ExP230 External vacuum pump, 230V
SEMS-PPSoft Post-processing software to allow off-line inversion
RackS SEMS Rackmount kit for 19" instrument racks
SEMS-Kit Maintenance kit for SEMS

Related Products

Contact us to discuss how Brechtel can help you.