Meteorological Particle Spectrometer

This precipitation-measuring optical disdrometer, used by the National Weather Service for rain and drizzle research, measures the size distribution, fall velocity, and rain rate of droplets from 50 µm to greater than 6.4 mm.


Identify precipitation type with 2D imaging of precipitation particle sizes and shapes and a 1D histogram of particle sizes. Post processing enables derivation of rainfall rate and intensity.

Overcome the elements with optical heads that are heated to prevent the window from becoming coated with fog or frozen precipitation.

Rely on the included wind vane to align sample path with wind flow, and use the free-standing swivel-mount for extended versatility.

Particle imaging

  • Light from a laser diode is shaped into an elliptical beam to illuminate the volume where the drops are detected.
  • The light and the shadow of a drop in the beam are then imaged onto a 64-element photo-diode array, such that a 50 micron drop will shadow one element and a 3,200 micron drop would shadow the whole array.
Measured Parameters Single-particle light imaging
Derived Parameters Particle diameter Particle number concentration Liquid water content (LWC) Effective diameter (ED) Median volume diameter (MVD)
Technique 64-element diode array, 20-cm path length
Resolution 25, 50 or 100-micron resolution (specify when ordering)
Particle Size Range 50 µm to >6.4 mm (maximum size depends on probe resolution)
Number Conc. Range 0 - 2,000 particles/cm3
Particle-by-particle Fall Velocity 5 - 500 cm/sec
Inter-arrival Time of Particles 0.001 - 100 sec
Communications High-speed serial RS-422; USB
Software Optional PADS software provides data analysis tools to display, record and play back data
Power Requirements Powered by 115 V / 60 Hz or 230 V / 50 Hz (specify when ordering) Power consumption: 200 W

PADS software and laptop

The Lifecycle Care Program ensures MPS 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.