Ultra-High Sensitivity Aerosol Spectrometer Airborne (UHSAS-a)

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



  • Aerosol research
  • Atmospheric and air pollution monitoring and research
  • 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
  • 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 and powerful LabVIEW software to facilitate 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 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 65 nm.




Parameter Specification
Measured Parameters Particle diameter (derived from single-particle light scattering)
Auxiliary Parameters Temperature
Particle Size Range 65 nm – 1 µm
Number Conc. Range 0 - 3,000 particles/second
Sampling Rate 1 or 10 Hz
Lasers Solid-state Nd3+:Y LiF4: ~1053 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
Flow Range Sample flow: 1 – 100 standard cm3/minute (typically 50)
Sheath flow: airflow setting is 700 ccm at sea-level, 590 Sccm at factory in Boulder, Colorado

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
Recommended Service Annual cleaning and calibration at DMT service facility
Computer Intel® Core i5-3210M processor
4.0 GB RAM

320 GB hard drive
Software UHSAS Executable program written in LabVIEW (included)
Data Recording Output file written to computer hard drive
Output data sent to serial port
Communications Output Serial

Power Requirements Instrument: 100-240 VAC, 47-63 Hz, 200W
Anti-ice: 28 VDC, 215W

Fuse: BUSS fuse, GMA-2A
Environmental Operating Conditions Temperature: -40 - +40 °C
Relative Humidity: 100%, non-condensing Altitude: 0 - 12,000 meters
Dimensions 16.5 cm diameter x 98 cm long
Weight ~16 kg

Specifications are subject to change without notice.


Included Items

  • Instrument
  • Shipping Case
  • Operator Manual
  • One-year warranty
  • One day of training at DMT facility
  • Email and phone technical support

Accessories (Purchased separately)

  • PADS software and laptop
  • Spinning pinhole for alignment and calibration check
  • Canister adapter—allows the CDP to be used with conventional cloud probe mounting canisters


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


  • Particle-by-particle feature that supplies information on individual particles, including inter-particle arrival times
  • Bidirectional serial stream communication control
  • Laminar flow element (LFE) for sample flow measurement

Included Items

  • Instrument
  • Laptop Computer
  • Operator Manual
  • Zero-count Filter
  • One-year warranty
  • One day of training at DMT facility
  • Email and phone technical support


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

C. A. Brock, J. Cozic, R. Bahreini et al. "Characteristics, sources, and transport of aerosols measured in spring 2008 during the aerosol, radiation, and cloud processes affecting Arctic Climate (ARCPAC) Project." Atmos. Chem. Phys., 11, 2423–2453, 2011. doi:10.5194/acp-11-2423-2011. Link

Moore, R. H., Bahreini, R., Brock, C. A., Froyd, K. D., Cozic, J., Holloway, J. S., Middlebrook, A. M., Murphy, D. M., and Nenes, A. "Hygroscopicity and composition of Alaskan Arctic CCN during April 2008" Atmos. Chem. Phys. Discuss., 11, 21789-21834, doi:10.5194/acpd-11-21789-2011, 2011. 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

Akua Asa‐Awuku, Richard H. Moore, Athanasios Nenes, Roya Bahreini, John S. Holloway, Charles A. Brock, Ann M. Middlebrook, Thomas B. Ryerson, Jose L. Jimenez, Peter F. DeCarlo, Arsineh Hecobian, Rodney J. Weber, Robert Stickel, Dave J. Tanner, and Lewis G. Huey. "Airborne cloud condensation nuclei measurements during the 2006 Texas Air Quality Study." J. of Geophys. Res., Vol. 116, D11201, doi:10.1029/2010JD014874, 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