MEASUREMENT VARIATIONS IN REFERENCE SPRAYS FOR NOZZLE CLASSIFICATION

Abstract

Variations in spray droplet measurements were identified for reference nozzles serving as category thresholdsdefined for the standardized classification of agricultural spray nozzles. Spraying Systems, Delavan, and Lurmarkmanufactured brands of reference nozzles produced mean volume median diameters (Dv0.5) that varied from 0.5 to 34 mwithin a given nozzle size, as measured with a laser diffraction instrument. Similarly, mean Dv0.1 and Dv0.9 values differedfrom 0.1 to 14 m and from 0.9 to 74.2 m, respectively. Coefficients of variation (CV) in Dv0.1, Dv0.5, or Dv0.9 within anozzle brand and size ranged from 0.19 to 3.62% across the test. Two additional laser instruments that were testedincluded an imaging probe and a phase Doppler instrument. Relative droplet size differences between nozzle brands werenoted when using different types of laser instruments compared with number density weighted values. Similarly, dropletsize differences were observed between instruments compared with number flux weighted values. Results indicate thatdedicated reference nozzle sets may be preferred to increase the overall uniformity of classification thresholds; any of thetested brands of nozzles would be suitable; and laser instrument differences may contribute to relative shifts amongthresholds for nozzle classification, thereby reducing the precision of uniform nozzle classification.