Measuring droplet impact with piezoelectric film

Abstract

The objective of this research was to develop a measurement system for determining droplet impact in the field with piezoelectric film. The piezoelectric film generates an output signal when it is deformed. The signals are analyzed with a data acquisition system (a computer with two high speed boards). Eight piezoelectric films were calibrated in the laboratory. Each film was calibrated by releasing various water droplet sizes from different heights. The signal output of film was then related to the kinetic energy of the droplet. The maximum droplet diameter generated was 5.6 mm, and the maximum height used was 4.59 m. To simulate a kinetic energy for larger droplets and higher elevations, a solid particle with 9.9 mm diameter and 0.5 gram mass was used. The results show that, in general, the output of piezoelectfic film responds linearly to kinetic energy. However, due to the size of the film used and deformation of large droplets upon impact, the output become non-linear and may be represented by Y=ax1 +bx2 +cx1cx2+dx12x2+ex13x2 + where, y = sensor output a, b, c, d, e = constants which depend on the characteristics of the film X1 = the kinetic energy X2 = I for the solid particle X2= 0 for water drops The measurement system was tested in the field. The results showed that this system could be used to measure droplet impact force at different places on plants.