Cloud Droplet Probe

This miniature, lightweight, low-power cloud particle spectrometer measures droplets in the range of 2 µm to 50 µm in concentrations as high as 2,000 particles/cm3.


Gather data across a wide range of platforms, including aircraft, towers, UAVs, and spray rigs.

Avoid particle fragmentation that can lead to overestimating particles thanks to anti-shatter tips and wetless windows.

Rely on the dynamic baseline feature to automatically adjust both sizer and qualifier signals to accommodate temperature drifts and ensure accurate particle sizing.

Get precise information on particle scattering intensity and inter-arrival times that are accurate to within a microsecond with the optional Particle-by-Particle Feature (PBP).

Particle light-scattering

  • CDP is a forward-scattering optical spectrometer that accepts and sizes only particles that pass through a region of the laser beam with uniform power.
  • Forward-scattered light is collected, directed through a 50/50 optical beam splitter, then measured by photodetectors to determine size and depth of field.
Parameter Specification
Measured Parameters

Single-particle light scattering

Derived Parameters

Particle diameter
Particle number concentration
Liquid water content (LWC)
Effective diameter (ED)
Median volume diameter (MVD)

Particle Size Range

2 – 50 µm

Number Conc. Range

0 – 2,000 particles/cm3

Typical Sample Area

0.24 mm2

Number of Size Bins


Air Speed Range

10 – 250 m/sec

Sampling Frequency

Selectable, 0.04 to 20 seconds

Refractive Index

Non-absorbing, 1.33 (the industry standard for water)

Light Collection Angles

Optical design: 4° – 12°
Optical performance: 1.7° – 14°


658 nm, up to 50 mW

Data System Interface

RS-422; USB

Power Requirements

System Power: 28 VDC at 2A
Anti-ice Power: 28 VDC at 12A

Environmental Operating Conditions

Temperature: -40 to 40 °C
Relative Humidity: 0 – 100%, non-condensing
Altitude: 0 – 50,000 feet (0 – 15,000 meters)


Probe: 1.37 kg / 3.0 pounds (standard version); a lightweight UAV version is also available
Electronics box and header cable: 0.82 kg / 1.8 lb

Probe Dimensions

26.7 cm L x 17.5 cm W x 21.6 cm H (10.5” L x 6.9” W x 8.5” H)

Electronics Box Dimensions

17.8 cm L x 8.9 cm W x 5.1 cm H (7.0” L x 3.5” W x 2.0” H

  • PADS software and laptop
  • Spinning pinhole for alignment and calibration check
  • Canister adapter – allows the CDP-2 to be used with conventional cloud probe mounting canisters

Droplet offers a three-year service plan to ensure that your CDP-2 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 CDP-2 include:

  • Shipping to and from Droplet facility for service
  • Incoming instrument evaluation and health check
  • Optical component inspection and cleaning
  • Clean and replace heater heatsink compound
  • Laser evaluation and adjustments
  • Dump spot monitor check
  • Alignment of laser splitter block
  • Offset voltage verification
  • Baseline amplitude verification
  • Check baseline voltages on DSP board and PADS
  • O-ring replacement
  • Hardware replacement
  • Reseal all windows
  • Calibration of instrument using Spinning Pinhole calibrator
  • Calibrate sizing with Soda Lime Glass Microspheres
  • Beam mapping of probe
  • Extreme cold testing of probe
  • Software, firmware, and antivirus update
  • 100% unit functionality tests
  • Certificate of Conformance, Calibration Certificate, Pitot Calibration Report, Pre-Cal and Post-Cal sizing histograms and housekeeping data 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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