OPTICAL SENSOR SYSTEM FOR CHEMICAL FLOW RATE MONITORING WITH DIRECT NOZZLE INJECTION

Direct injection systems have the potential to provide several benefits to spray applicators (e.g., easing boom cleanout procedures); however, lag time and proper mixing continue to hinder adoption. Development efforts have typically focused on moving the chemical injection point closer to the nozzle to improve the application rate response. This poses an important challenge for proper metering of the chemical, i.e., accurate measurement of extremely low chemical flow rates. In this study, an optical sensor system was integrated with a typical carrier flowmeter and calibration methodology to measure chemical flow rates for a direct nozzle injection sprayer. The optical sensor used a light-emitting diode (LED) and photodiode pair to measure the absorbance of a dye mixed with a simulated chemical solution. Laboratory tests were conducted to evaluate the measurement accuracy of the system in which sensor output was compared directly to measurements from a spectrophotometer. Results indicated that the calibrated sensor system was able to estimate the simulated chemical flow rate with an average error of 2%. The sensor system was also capable of accurate measurements as the initial concentrations of dye mixed with the chemical solution varied.