Back-Scatter Cloud Probe

The BCP is a compact probe that measures 5 µm to 75 µm particles with no contamination from ice crystal shattering and no airflow distortion.


Minimize airflow disturbance and enable undisturbed particle measurement with the BCP’s aerodynamic design. Mount the BCP easily on aircraft, even when space is at a premium.

Monitor multiple output variables like total particles, average transit time, over-range particles, and various probe health indicators.

Depend on automatic adjustments to both sizer and qualifier signals to account for temperature drifts and ensure accurate particle sizing.

Program the instrument's sample rate and size bin thresholds. Plus, get size distributions accumulated in the probe, with serial transmission to a computer via any standard RS-232 or RS-422 communications port.

Particle light-scattering

  • Particles passing through the laser beam scatter light in all directions.
  • Light transmitted within a cone with subtending angles between 143° and 169° (156° ± 13°) is directed onto a photodetector that converts photon pulses into electrical pulses, which are then transmitted to a signal processor that amplifies and digitizes them.
  • Mie theory is used to determine the particle’s size from the peak amplitude of the scattering signal, then used to determine particle number concentration.
Measured Parameters Single-particle light scattering
Auxiliary Parameters Temperature Pressure
Derived Parameters
  • Particle diameter
  • Particle number concentration
  • Liquid water content (LWC)
  • Effective Diameter (ED)
  • Median volume diameter (MVD)
Particle Size Range 5 - 75 µm
Number of Size Bins
  • 10, 20, 30, or 40 (configured at time of purchase)
  • User-Selected boundaries
Number of Concentration Range 0 - 1,000 particles/cm3
Air Speed Range 10 - 250 m/sec
Sampling Frequency Selectable, .04 sec to 20 sec
Light Collection Angles Center-line: 156°, +/- 13° (see "How it Works" diagram)
Laser 658 nm
Laser Power 50 mW or less
Data System Interface RS-422 serial interface
Environmental Operating Conditions
  • Temperature: -40° to 40°C
  • Relative Humidity: 0 - 100%, non-condensing
  • Altitude: 0 - 50,000 feet (0 - 15,000 meters)
Weight 1.5 kg
Probe Dimensions 11.7 cm x 10.7 cm x 4.5 cm, with 5.9 cm diameter mounting flange
Electronic Box Dimensions 21.6 cm x 12 cm x 5.7 cm
Power Requirements 28 VDC, 5 A for system and heaters

The Lifecycle Care Program ensures BCP integrity and performance vital to your research mission for 3 years or 3 calls (whichever comes first). When conducting complex and time intensive laboratory or field measurements it is critical to avoid down time, and ensure data collection accuracy. The program consists of 3 key deliverables for each year or call:

  • Instrument Logistics
  • Instrument Integrity
  • Instrument Performance

Lifecycle Care Program Includes:


  • Shipping to and from Droplet Measurement Technologies facility
  • Customs handling, including CARNET ATA if required


  • Incoming instrument evaluation and health check


  • Software and firmware validation
  • 100%-unit functionality test
  • Calibration data
  • Calibration report
  • Certificate of calibration

At times, our technician might discover an instrument issue, which might not be covered by the Lifecycle Care Program or by our product warranty. In such case we will reach out to you with a service & repair estimate to allow you to provide us with the next steps of action.