Ultra-High Sensitivity Aerosol Spectrometer (UHSAS)


An optical spectrometer that measures particles in the 0.06 µm to 1 µm range.
Special features: Ultra-high resolution




  • Aerosol research
  • HEPA/ULPA filter testing and characterization
  • Atmospheric and air pollution monitoring and research
  • Chemical process monitoring and control
  • Pharmaceutical research and manufacturing
  • Powders and food products research
  • Inhalation toxicology research
  • Combustion and emission source research
  • Nebulization analysis
  • Coalescence and nucleation research


Superior Resolution

UHSAS accurately sizes even the smallest particles. The graph at right shows the results of a test conducted with 95 nm and 104 nm standard PSL particles. Although these particle diameters are only 9 nm apart, the UHSAS has correctly identified two distinct particle peaks.


Other Advantages

  • Eliminates sizing uncertainty associated with scattering spectrometers that measure at sizes larger than the excitation wavelength. 
  • Categorizes particles by size in up to 100 bins (user selects number of bins and boundaries)
  • Counts up to 3,000 particles/second
  • Uses aerosol spectrometry technique with two detection systems: a primary, highly sensitive APD-based system to size smaller particles, and a secondary PIN photodiode system to size larger particles
  • Compensates for small drifts in laser power via automatic gain control
  • Features an on-board computer, built-in monitor, and powerful LabVIEW-designed software for easy, real-time data analysis



The UHSAS comes with LabVIEW-designed software that provides a user-friendly virtual instrument panel for the control and data display of the UHSAS. For instance, the program enables the user to do the following tasks:

  • Start data recording and sampling
  • View a histogram of particles binned by diameter, by transit time, or by peak optical signal
  • Set boundaries for the histogram bins
  • Control sample flow and monitor temperature, pressure, and laser current
  • Calibrate the instrument



How It Works

A laser illuminates particles, which scatter light that is then collected by two pairs of Mangin optics. One pair of optics images onto a highly sensitive avalanche photodiode (APD) for detecting the smallest particles. The other pair images onto a low-gain PIN photodiode for detecting particles in the larger size range of the instrument. Each detector is amplified in a current-to-voltage stage that feeds into the analog electronics system. The amplification allows the system to detect particles as small as 60 nm. 



Parameter Specification
Auxiliary Parameters Temperature
Derived Parameters Particle diameter
Number Concentration Range 3,000 particles/second
Particle Size Range 60 nm – 1 µm
Aerosol Medium Air, 0 - 30 °C (32 - 86°F) 
  • Solid-state Nd3+:Y LiF4: ~1054 nm, 1 kW/cm2 intracavity circulating power 
  • Pump Laser: ~797 nm, 1.6 W
Number of Size Bins 100 max:
  • 99 standard bins (98 if both overflow and underflow are enabled) 
  • One overflow bin and one underflow bin
Sample Flow
  • Standard option: 1 – 100 standard cm3/minute (typically 50) 
  • Other options available
Flow Control Controlled from software; can also be manually adjusted via mass or volume flow controller 
Routine Maintenance Daily:
  • Monitor laser power by verifying Laser Reference voltage falls within acceptable levels; if necessary, clean critical optics to restore laser power
  • Zero check with high-efficiency filtered air sample 

Monthly and around field campaigns: 
  • Full-scale calibration

  • Flow controller calibration 
Calibration The UHSAS, with its high resolution and large number of arbitrarily settable bins, requires a complex process to ensure accurate calibration. However, the UHSAS software automates much of this process, making it a simple matter to calibrate the instrument on a daily basis.

Calibration is accomplished by adjusting the instrument’s four gain stages so particles are accurately sized. First, gain stages are adjusted relative to each other, and then the scale is fixed to a known particle size using monodisperse polystyrene latex (PSL) spheres. The combination of relative and absolute gain calibration ensures that the UHSAS is properly measuring particles.
Recommended Service Annual cleaning and calibration at DMT service facility 
Front Panel Display Built-in monitor, 2 USB 2.0 ports
Rear Panel Connections System power switch, system power connection, Ethernet, exhaust vent, exhaust port, serial stream connection 
Computer System On-board Intel®Celeron™ CPU
504 MB RAM
80 GB hard drive for data storage
User interface via standard keyboard, mouse, and built-in monitor (included) 
Software Executable program written in LabVIEW
Data Recording
  • Output file written to computer hard drive
  • Output data sent to serial port 
Communications Output Serial, Ethernet, USB
Power Requirements 100-240 VAC, 47-63 Hz, 200W
Dimensions 56 cm L x 43 cm D x 24 cm H
Environmental Operating Conditions Temperature: 0 – 30°C (32 - 86°F) 
RH: 0 – 100% RH non-condensing 
Altitude: Sea level to 4 km

Specifications are subject to change without notice.

The UHSAS is a Class I Laser Product with a Class IV pump laser, U.S. Patent # 5,889,589.


How to Order

Contact DMT for pricing or more information.

Email: customer-contact@dropletmeasurement.com

Phone: +001 303 440 5576
Fax: +001 303 440 1965


Included Items

  • Instrument
  • Keyboard with touch pad
  • Operator manual
  • Zero-count filter
  • Domestic and international power supply
  • One day of training at DMT’s facility
  • One-year warranty

Options and Accessories (Purchased Separately)

  • Rack mountable unit (standard 19” instrument rack)
  • External laptop (for remote applications, replaces flat screen display)
  • Particle by particle feature (supplies information on individual particles, including inter-particle times)
  • Bidirectional serial stream communication control


How to Order

Contact DMT for pricing or more information.

Email: customer-contact@dropletmeasurement.com

Phone: +001 303 440 5576
Fax: +001 303 440 1965


Selected Bibliography

Y. Cai, D. Montague, W. Mooiweer-Bryan, and T. Deshler, “Performance characteristics of the ultra high sensitivity aerosol spectrometer for particles between 55 and 800 nm: Laboratory and field studies,” Journal of Aerosol Science 39 (2008) 759-769. Link

R. Yokelson, I. R. Burling, S. P. Urbanski, E. L. Atlas, K. Adachi, P. R. Buseck, C. Wiedinmyer, S. K. Akagi, D. W. Toohey, and C. E. Wold, “Trace gas and particle emissions from open biomass burning in Mexico,” Atmos. Chem. Phys. Discuss. 11, 7321-7374, 2011. doi:10.5194/acpd-11-7321-2011.Link

R. Yokelson, S. Urbanski, E. Atlas, D. Toohey, E. Alvarado, J. Crounse, P. Wennberg, M. Fisher, C. Wold, T. Campos, K. Adachi, P. R. Buseck and W. M. Hao. "Emissions from forest fires near Mexico City." Atmos. Chem. Phys. Discuss. 7, 6687–6718, 2007. Link