A Turbidity Module to Measure Spray Mixture Concentration for Premixing In-Line Injection System

Highlights A turbidity sensor module was investigated to monitor concentrations of pesticide mixtures in real time. A flow-through measurement platform was built to calibrate the turbidity sensor and determine its accuracy. Optimal location of the turbidity sensor was determined for monitoring in-line mixture concentrations. Spray mixture uniformity reached acceptable level for the premixing in-line injection system. Abstract. Monitoring mixture concentrations for precision pesticide spray systems in real time can assure the desired amount of chemicals distributed uniformly to target areas. An in-line turbidity sensor module was investigated to monitor concentrations of spray mixtures produced with a premixing in-line injection system developed for precision variable-rate orchard sprayers. The turbidity sensor was calibrated with simulated pesticides at concentrations ranging from 0% to 30.0%. A cubic polynomial regression model was established for the relationship between sensor output voltages and mixture concentrations. Sensors were mounted at three in-line locations to detect the mixture uniformity differences in the premixing in-line injection system. The module was found to have adequate precision and accuracy to measure concentrations of spray mixtures with simulated pesticides. Relative errors of the sensor were less than 4.70% and the sensor accuracy did not vary with mixture flow rates. Mounting the turbidity sensor downstream of the buffer tank in the premixing in-line injection system would be the optimal location to monitor spray mixture uniformity for variable-rate spray applications. At this location, the relative errors of measured mixture concentrations were between 0.12% and 3.70% which agreed with previous manual measurements. Therefore, there would be a great potential to integrate the in-line turbidity sensor into the variable-rate and even conventional constant-rate sprayers to achieve uniform spray applications in the target field. Keywords: Agitation, Mixture uniformity, Pesticide concentration, Sensor calibration, Variable-rate sprayer.