Cloud Combination Probe (CCP)



A multipurpose, simple-to-use cloud spectrometer that includes three DMT instruments plus temperature and relative humidity sensors.
Special Features: Particle-by-particle data, grayscale imaging, finer resolution, anti-shatter tips (all optional)




  • Cloud particle research
  • Climate studies
  • Aircraft icing
  • Hurricane and storm research
  • Weather modification
  • Agricultural and industrial spray characterization

Photo: the CCP being used to conduct icing certification tests on Boeing 787 engines.



The CCP is an ideal choice for those who want an all-purpose, simple-to-use cloud probe. Five instruments are packaged into a single canister and integrated measurement system. The CCP provides the following data:

  • Aerosol particle and cloud hydrometeor size distributions from 2 to 50 μm
  • Two dimensional images and precipitation size distributions from 25 μm to 1550 μm (or 2 μm to 930 μm if the CIP component is ordered with 15-μm resolution)
  • Liquid water content from 0.05 to 3 g/m3
  • Aircraft velocity and altitude
  • Atmospheric temperature, pressure, and relative humidity


Optional Features

Standard CDPs provide particle-size information in histogram form but do not provide precise size data for individual particles. The PBP version of the instrument offers more precise information on individual particle sizes. For the first 256 particles detected during every sampling instance, the PBP component generates the following data:

  • Particle size in digital counts (which can be used to determine particle size in μm)
  • Individual particle time with μsec resolution
  • Inter-arrival particle time (IPT), i.e., the time in msec that has elapsed between qualified particles

PBP data are useful when investigating small-scale cloud structure to identify mixing and entrainment, drop breakup and coalescence, and micro-scale turbulence.

Grayscale imaging provides detail about particle composition that is missed with monoscale imaging. In particular, grayscale imaging gives three levels of shadow recording on each photodetector as opposed to one. The pictures below show the same particles recorded with grayscale imaging (left) and monoscale imaging (right).


The CIP is offered in a 15 µm resolution as well as the standard 25 µm resolution.
The CIP can be purchased with special Korolev anti-shatter tips, shown below. Korolev tips significantly reduce the incidence of particle artifacts in the sample area.


The CIP can be purchased with 28 VDC or 115 VAC anti-ice heaters.



Two optional software packages are available  for CAPS users. The Particle Analysis and Display System (PADS) allows for instrument control and real-time data display.

The second software package, the Optical Array Shadow Imaging Software (OASIS), facilitates post-processing particle analysis. More information about these two packages is given below.


Particle Analysis and Display System (PADS)

PADS displays a user-friendly virtual instrument panel that enables the user to do the following tasks:

  • Start data recording and sampling
  • View particle image data acquired with the CIP
  • View particle volume and number concentrations, as well as Median Volume Diameter (MVD) and Effective Diameter (ED)
  • View LWC as measured or calculated by the hotwire sensor, CIP, and CDP
  • Monitor instrument parameters like CIP laser current and various electronics voltages
  • Play back data for post-flight viewing

Online PADS Software Manual



Optical Array Shadow Imaging Software (OASIS)

OASIS, shown at right, is designed for rigorous post-processing analysis. It provides additional particle statistics beyond those generated by PADS. In addition, OASIS allows users to filter particles by various criteria, including particle area, particle shape, area fraction, and inter-arrival time. Written in IGOR Pro, OASIS leverages IGOR’s robust statistical analysis features for enhanced data analysis and graphing capability. 


How it Works


The three DMT instruments included in the CCP are the Cloud Imaging Probe (CIP), the Cloud Droplet Probe (CDP), and the Hotwire Liquid Water Content Sensor (Hotwire LWC).

The CIP, which measures larger particles, operates as follows. Shadow images of particles passing through a collimated laser beam are projected onto a linear array of 64 photodetectors. The presence of a particle is registered by a change in the light level on each diode. The registered changes in the photodetectors are stored at a rate consistent with probe velocity and the instrument’s size resolution. Particle images are reconstructed from individual “slices,” where a slice is the state of the 64-element linear array at a given moment in time. A slice must be stored each time interval that the particle advances through the beam a distance equal to the resolution of the probe.

The CDP, which measures smaller particles, relies on light-scattering rather than imaging techniques. Particles scatter light from an incident laser, and collecting optics guide the light scattered in the 4° to 12° range into a forward-sizing photodetector. This light is measured and used to infer particle size.

The Hotwire LWC instrument estimates liquid water content using a heated sensing coil. The system maintains the coil at a constant temperature, usually 125 °C, and measures the power necessary to maintain this temperature. More power is needed to maintain the temperature as droplets evaporate on the coil surface and cool the surface and surrounding air. Hence, this power reading can be used to estimate LWC. Both the LWC design and the optional PADS software contain features to ensure the LWC reading is not affected by conductive heat loss.


Parameter CIP Specification CDP Specification LWC Specification
Technique Optical Array Probe with 64 elements: 62 sizing elements, end diodes reject Light-scattering probe with 30 size bins Temperature-Controlled Hotwire Sensor
Measured Particle Size Range 12.5 µm – 1.55 mm (standard) 2 µm to 50 µm N/A; measured LWC range is 0 - 3 g/m3
Sample Area Variable; depends on tip configuration and particle size 0.24 mm2 N/A
Upper Concentration Range Depends on particle size, but up to 500 particles/ cm3 for a CIP with standard tips and arm width 2,000 particles/cm3 3 g/m3
Air Speed Range 10 - 300 m/s for 25 μm resolution CIP; 10 - 180 m/s for 15 μm CIP 10 - 250 m/s 10 - 200 m/s
Number of Size Bins 62 30 N/A
Sampling Frequency 1D histogram data: 0.05 to 25 Hz 
2D image data: variable interval, when buffer fills
Selectable, 0.05 to 25 Hz N/A
Laser 658 nm, 30 mW 658 nm, ~50 mW N/A
Calibration Verification Spinning glass disk with opaque dots of known size Precision glass beads Not Required
Non-absorbing Refractive Index N/A 1.33 (the industry standard for water) N/A
Light Collection Angles N/A 4° - 12° N/A
Auxiliary Parameters Ambient Temperature

Relative Humidity

Static Pressure

Dynamic Pressure
Data System Interface: 2D CIP data: RS-422, High Speed, 4 Mb/sec Baud Rate
System data: RS-232 or RS-422, 56.6 kb/sec Baud Rate
Optional Software Particle Analysis and Display System (PADS) for all instruments
Optical Array Shadow Imaging Software (OASIS) for the CIP
Weight 29 lbs./13.2kg for probe and canister
Power Requirements System Power bus: 28 VDC, 3A
Auxiliary bus (formerly “LWC bus”): 28 VDC, up to 8A (depends on LWC content)
CIP Anti-Ice bus: 28 VDC, 13A
CDP Anti-Ice bus:28 VDC, 7A
Environmental Operating Conditions Temperature: -40 °C to +40°C (-40 °F to +104 °F)
RH: 0 – 100%, non-condensing
Altitude: 0 - 50,000 ft
Routine Maintenance DMT recommends conducting basic instrument performance checks and inspecting the CIP optical windows before a flight. A weekly calibration check of the CDP and CIP is also recommended.

Specifications are subject to change without notice. CDP specifications apply to both standard CDP and CDP with the particle-by-particle feature.


Included Items

  • Instrument
  • Shipping case
  • Operator manual
  • Glass beads and dispenser for CDP calibration check
  • Spinning disk (pictured at right) for CIP calibration check
  • One day of training at DMT’s facility
  • One-year warranty

Accessories (Purchased separately)

  • Laptop and Particle Analysis and Display System (PADS) software
  • OASIS Software
  • Data Acquisition System


How to Order

Contact DMT for pricing or more information.


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

Selected Bibliography

Schuyler, H., M. Asselin, and D.Baumgardner. “Observations of ice ridge formation on the SJ30-2 leading edge slat in freezing drizzle conditions.” SAE Technical Paper 2007-01-3365, 2007, doi:10.4271/2007-01-3365. Link