PDI: Phase Doppler Interferometer
Droplet size and velocity measurements

PDI Advantages

Advantages of the PDI Method for Particle Sizing

Measurements are based on the wavelength of light that is known to high accuracy and does not change due to environmental conditions
The size of the sample volume can be easily controlled and made as small as the largest droplet to be measured (or even smaller)

Response is to ballistic or singly-scattered photons; secondary light scattering
is not detected
Signals have a unique sinusoidal character making them easily detectable
with high reliability using digital techniques
Simultaneously measures the size, velocity, and time-of-arrival of every drop
Forms a direct measurement of the size distribution
Droplet size range capability of 0.5 μm to 2000 μm or greater
LWC capability from 0 to 100g/m3 or larger
Measures in droplet number densities to 100,000/cc, depending on droplet size
High data rate capability of >100,000 drops/second without loss of readings
In situ measurements of the sample volume size allowing determination of droplet number density, flux and LWC
Reliable detection and rejection of ice particles from the droplet size measurement

Key features that are unique to Artium’s PDI include:

Built-in, high-powered DPSS lasers to enable backscatter measurements through contaminated windows.
Automated instrument setup features to simplify instrument operation in difficult environments (U.S. Patent 7,564,564, 2009)
Digital signal detection and full complex Fourier transform signal processing for frequency and phase
Automatic selection of size range through computer selection of beam intersection angle and beam expansion
Automatic selection of size range through computer controlled mask selection in the receiver covering at least three size ranges
Signal intensity validation logic
Three phase measurements for improved particle measurement reliability and accuracy and rejection of trajectory errors
Option fourth phase measurement for improved measurement accuracy in dense spray application
Full complex Fourier transform signal processing with up to 100,000 samples in the signals
Advanced signal validation logic including tests for variations in frequency and phase over the duration of the Doppler signals (U.S. Patent Pending)
Computer selectable sample volume size to minimize coincidence errors