Design and experiment of pesticide droplet deposition detection system based on principle of standing wave ratio

Abstract: In order to realize the rapid acquisition of droplet deposition after application, this study proposed an interdigitated droplet collecting board structure based on standing wave ratio principle. The purpose of this study was to quickly and effectively obtain the characteristics and regularity of the droplet deposition distribution. On one hand, the system could reduce the experiment cost, the difficulty of operation and the complexity of the experiment. On the other hand, the system was important to evaluate the quality of pesticide application and improve the utilization rate of pesticide. Optimized droplet deposition detection technology could solve the problem of single measurement method and low efficiency of droplet deposition distribution in field, which was a goal pursued by scholars in this research field. Based on the principles of standing wave ratio and sensor network technology, the real-time detection system of droplet deposition on the ground was designed. The droplet distribution characteristics of the electric field were explored by the method of simulation, and then the optimal parameters of the interdigitated droplet collecting board were obtained. At the same time, combined with the greenhouse self-propelled sprayer system, the application test and verification test were carried out to obtain the distribution characteristics of droplet deposition accurately and quickly. The real-time detection system of droplet deposition in the greenhouse could be realized by using the method of standing wave ratio, and the reliability was very high. At the same time, the system had great practical significance in the field of droplet spray quality detection and regularity research. In order to verify the rationality of the interdigitated droplet collecting board structure, the electromagnetic simulation of the system was carried out by using the three-dimensional electromagnetic simulation software HFSS (high frequency structure simulator). The device took the STM32 single chip microcomputer as its core to build the ZigBee network, and the signal of the droplet collection sensor was transmitted to the remote terminal based on LabView2014 through the RS232 serial port, which realized the real-time monitoring of the droplet deposition. The results of the HFSS model showed that the electrostatic shielding appeared inside the interdigitated droplet collection board. The electromagnetic coupling could be realized by the droplets between the boards, which could be used to detect the droplet deposition. The sensitivity of the system would be decreased with the board spacing broadening. The regression equation of the relationship between the output voltage of the detection system and the deposition amount of the reagent solution was established through the calibration experiment. The determination coefficients under 2 different dielectric constants were 0.982 1 and 0.997 6 respectively. The 3W-ZW10 type self-propelled sprayer application test in greenhouse showed that the maximum relative error rate of the simulated value of the deposition amount of the system at the sampling point was not more than 7.95%. The RMSE (root mean square error) of the measured value was 0.076 7 mg/cm2. The detection accuracy of droplet deposition was high. The droplet deposition amount detection system can be used for rapid measurement of field droplet deposition rate based on the principle of standing wave ratio. From the laboratory calibration and application test results, it can be concluded that the design of the interdigitated droplet collection system is feasible within the range of 300 μm particle size. The proposed real-time detection method of droplet deposition in greenhouse based on the standing wave ratio is suitable for the detection of the droplet spray quality and the characteristics of droplet distribution. This research can provide reference for the measurement of droplet deposition.