A chamber for scanning spray from agricultural nozzles using an Aerometrics phase/doppler particle analyzer

The Aerometrics Phase/Doppler Particle Analyzer (PDPA) is a laser based particle analyzer capable of non-intrusive measurement of the droplet diameter and velocity of a variety of sprays. A chamber suitable for three dimensional scanning of sprays produced by agricultural nozzles, as well as for safe handling of pesticides, is described. The chamber, constructed entirely of corrosion- resistant materials, contains a computer controlled three-dimensional traversing system for moving the nozzle, glass walls and a sump for collecting the spray liquid, air ventilation for removing vapours, a liquid delivery system capable of monitoring flow rate and pressure, and a wash-down nozzle for removing pesticide residues. Evaluation of the PDPA system in conjunction with the chamber, using tap water as the spray solution, indicated the following: a) there was good overall measurement consistency of the PDPA system from day to day; b) the glass walls of the chamber reduced PDPA laser beam intensity, resulting in decreased sensitivity for small droplets; and c) the presence of the fan induced downdraft in the chamber increased average droplet velocity and increased the number of small droplets detected. In all cases, observed effects were minor and were not considered to be of practical significance with respect to the PDPA's accuracy.