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.
Parameter Specification
Measured Parameters

Single-particle light imaging

Derived Parameters

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


64-element diode array, 20-cm path length


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


High-speed serial RS-422; USB


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

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

  • Shipping to and from Droplet facility for service
  • Incoming instrument evaluation and health check
  • Optics cleaning & alignment
  • O-ring replacement
  • Hardware replacement
  • Bearings inspection and replacement
  • Baseline voltages set and verified
  • Heater testing
  • Laser alignment
  • Software, firmware, and antivirus update
  • Calibration of instrument using spinning disk calibrator
  • 100% unit functionality test
  • Calibration data, Calibration Report, Certificate of Calibration 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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