Passive Cavity Aerosol Spectrometer Probe

The PCASP-100X is an airborne optical spectrometer that measures aerosol particles in the 0.1 µm to 3 µm range.


Get unmatched sensitivity and specificity in real-time measurements of aerosols.

Enable direct measurement of the air stream with the leading cannister-based aircraft instrument.

Power your research with elimination of dead-time losses, plus continuous monitoring of multiple housekeeping variables.

Get user-programmable sample rates, number of channels, and channel size thresholds.

Particle light-scattering

  • Optical bench collects light that is scattered by individual particles passing through a HeNe, 0.6328 µm laser beam.
  • An amplification system with three gain stages covers the full range of particle sizes.
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


HeNe multi-mode classical passive cavity, wavelength 0.6328 µm

Light Collection Angle

Nominally 35° – 120°

Data System Interface

RS-422, 34800 baud rate; USB

Power requirements

Probe: 115VAC or 230VAC, 50-60Hz, less than 120W; specify voltage when ordering
Anti-ice: 28 VDC, 215 W


40 lbs (18.2 kg)


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)

PADS software and laptop
Data Acquisition System
Aerosol Generator

Droplet offers a three-year service plan to ensure that your PCASP-100X continues to deliver high-quality data. This plan locks costs upfront at the time of funding application and covers annual calibration, alignment, cleaning, wear-item replacement, calibration documentation, and shipping. Specific services provided for the PCASP-100X include:

  • Shipping to and from Droplet facility for service
  • Incoming instrument evaluation and health check
  • Optics cleaning and alignment
  • O-ring replacement
  • Hardware replacement
  • Replace heat sink compound
  • Baseline voltages set and verified
  • Power supply evaluation
  • Flow measurement verification
  • Card edge connectors cleaning
  • Heater testing
  • Inlet jet alignment
  • Desiccant replacement
  • Calibration of instrument using Aerosol Generator and PSL’s
  • Canister test
  • Software, firmware, and antivirus update
  • 100% unit functionality test
  • Calibration data, Calibration Report, Certificate of Conformance provided

Talk to an expert

Speak with one of our scientists or experts at Droplet Measurement Technologies today to discover solutions that can power your research.

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