Passive Cavity Aerosol Spectrometer Probe (PCASP-100X)

An airborne optical spectrometer that measures aerosol particles in the 0.1 to 3 µm range.




  • Aerosol research
  • Air quality and visibility
  • Atmosphere and climate studies
  • Weather modification
  • Biomass burning studies

Photo: The PCASP-100X and other instruments mounted on a Russian research aircraft. Photo courtesy of the Central Aerological Observatory in Moscow.

The PCASP-100X is currently in use on research aircraft in over 20 countries.



  • Elimination of dead-time losses
  • Size distributions accumulated in the probe, with serial transmission to any standard computer communications port; this eliminates the need for special data systems or interfaces
  • User-programmable sample rates, number of channels, and channel size thresholds
  • Monitoring of multiple housekeeping variables




The Particle Analysis and Display System (PADS, right) is optional software that provides a user-friendly virtual instrument panel.

PADS allows the user to control the PCASP-100X and display real-time data and logs. For instance, the program enables the user to do the following tasks: 

  • Sample and record data
  • View particle volume and number concentrations, as well as Median Volume Diameter (MVD) and Effective Diameter (ED)
  • Monitor instrument parameters like laser reference voltage and other instrument-health indicators
  • Play back data for post-flight viewing
  • Reprocess data with new parameters for additional analysis

Online PCASP-100X Software Manual


How It Works

The PCASP-100X consists of an optical bench and signal processing electronics. The optical bench collects light that is scattered by individual particles passing through a laser beam. It then converts the photon pulses to an electron voltage pulse via an Avalanche Photo Detector. The electronics package amplifies, filters, digitizes and categorizes this voltage pulse before transmitting the digital value for processing by an external data system.

The scattered light intensity of the PCASP-100X’s particle sizing range covers more than six orders of magnitude. As a result, the instrument uses an amplification system with three gain stages. The high-gain stage amplifies the signal detector voltage by a factor of 45 greater than the mid-gain stage, and the mid-gain stage amplifies by a factor of 17 greater than the low-gain stage. This system allows the probe to accurately size all particles in its range.




Parameter Specification
Measured Parameters Particle size (determined from particle light-scattering)
Ambient temperature

Standard and volumetric flows for sample and sheath air
Derived Parameters Particle Concentration
Median Volume Diameter (MVD)
Effective Diameter (ED)
Particle Size Range 0.1 – 3.0 µm
Maximum Count Rate 3,000 particles/sec
Counting Efficiency 50% at minimum threshold, increasing to 100% by the fourth size channel
Sampling Frequency 0.1 to 25 Hz, selectable
Flow Rate Sample flow: 1 cc/sec
Sheath flow: 15 cc/sec
Air Speed Range 0 - 250 m/sec
Number of Size Bins Standard is 30
Laser HeNe multi-mode classical passive cavity, wavelength 0.6328 µm
Light Collection Angle Nominally 35° - 120°
Data System Interface RS-232 or RS-422, 34800 baud rate
Calibration PSL aerosol generator
Power requirements Probe: 115VAC or 230VAC, 50-60Hz, less than 120W; specify voltage when ordering
Anti-ice: 28 VDC, 215 W
Weight 40 lbs (18.2 kg)
Dimensions 40” long x 7” diameter (102 cm long x 18 cm diameter)
Operating Conditions Temperature: -30 to +40 °C
Altitude: 0 to 30,000 ft (9.1 km)
Relative Humidity: 0 - 90% RH (non-condensing)

Specifications are subject to change without notice.



Included Items

  • Instrument
  • Shipping Case
  • Operator Manual
  • Power and Serial Cablesl
  • One-year warranty
  • One day of training at DMT facility

Accessories (Purchased separately)

  • PADS software and laptop
  • Data Acquisition System
  • Aerosol Generator


How to Order

Contact DMT for pricing or more information.


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