The PDA system can perform
simultaneous non-intrusive
measurements of the size and the velocity of individual spherical
particles in liquids and gaseous flows. Phase Doppler anemometry is based on light-scattering
interferometry and therefore requires no calibration. The measurements are
performed at the intersection of two focused laser beams, which define the
measurement volume. The two laser
beams create an interference fringe pattern of alternating light and dark
planes. As particles pass through
the intersection, light is scattered onto multiple detectors, which converts the
optical signal into an electrical signal representing a Doppler burst.
The signal processor measures the phase difference between the Doppler
signals from the multiple detectors and calculates the particle diameter.
For further information on PDA's and
their uses at the ARES click here
