Spray Application Problems: LXIX. Assessment of the Droplet Spectra of Spraying Equipment with the Flying Spot Particle Resolver

Abstract

The measurement of droplet size is an important part of the assessment of the efficiency of crop-spraying and other droplet-generating equipment such as humidifiers. It is usually impossible to measure all the droplets produced by the equipment, and some form of sampling is necessary. 1Iedi3. for the sampling of aqueous drops include cells of oil in which the drops remain their spherical form, slides coated with a layer of magnesium oxide in which the impacting drops form circular depressions, and paper on which the drops of c. dye solution form individual stains. The last medium can also be used for oil drops, while the first two have the advantage that they can be used to collect a wide range of aqueous spray materials without the introduction of dyes. Sampling of the droplets in flight by photography is also possible. Until the recent introduction of automatic methods of counting and sizing, all these sampling methods have necessitated laborious and often inaccurate visual measurement by calibrated microscopes or projection apparatus. A critical review has been made by Furmidge (1) of the reliability and accuracy of a flying spot panicle resolver for the automatic measurement of the stains made by spray droplets of a nigrosine dye solution on fixed and glazed photographic paper. He found that the 3peed and reliability of this method were considerably greater than could be achieved by visual microscopic measurement and, given a reasonably skilled operator and suitable stain samples, the counting and sizing accuracy was also greater.