Spray Drop Size Measurement via Image Analysis

Application of Plant Protection Products (PPP) is affected by many factors. For spray applications, drop size is the most important feature as it affects all aspects of a phytosanitary treatment: biological efficacy, environmental pollution, and operator safety. This study proposes a custom system that allows measuring the drop size of agricultural spray nozzles under ordinary working conditions. The design of the equipment is mainly based on the ISO 5682-1 standard. Drops sprayed by the nozzle under test are trapped by a layer of silicone oil contained in Petri dishes and then photographed in situ with a DSLR camera. Digital images are then analyzed with an image analysis software capable of detecting all the drops. After a proper calibration, all parameters of the drop size distribution are obtained. A sensitivity analysis to evaluate the effects on drop size distribution of the calibration factor and the exclusion of very small particles that could be due to image noise is also carried out.