Development of a capacitive sensor for spray deposition and drift measurements

Techniques to detect droplet deposition and drift is needed to achieve precision spray applications on intended targets and minimize negative environmental impact. A novel capacitive sensor for detection of droplet deposition and drift was developed to provide quick feedback information on spray quality for pesticide applications. The relationship between the capacitance change (∆ C ) and the droplet mass ( m ) was analyzed. Five different designs of the sensor with different distances between plates ( d ) (0.535, 0.785, 0.985, 0.335 and 0.185 mm) were used to evaluate the sensor performance in detecting spray deposition and drift for water-based droplets of different volumes (0.5, 1, 2, 3, 4, 5, 6, 7 and 8 µL) with different solutions (TW, S1, S2 and S3). Results of the indoor experiments showed that ∆ C correlated with V a very well when d was small. The slopes between ∆ C and V a of different solutions varied with the density and dielectric constant. The data of spray deposition detection demonstrated that R 2 increased as d decreased. The proposed sensor would have great potential to provide a convenient tool for detection of droplet deposition and drift under various laboratory and field conditions, significantly improve the experimental efficiency especially for field experiments.