Graduate Studies


First Advisor

Joe D. Luck

Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agricultural and Biological Systems Engineering, Under the Supervision of Professor Joe D. Luck. Lincoln, Nebraska June, 2019.

Copyright 2019 Chandler Folkerts.


Direct injection sprayer systems that provide many benefits to operators and commercial systems are becoming increasingly available. Research efforts have furthered the ability and accuracy of these systems, but still face several engineering challenges. Research has focused on moving the injection point closer to nozzle at the boom for faster control of application rates which poses many problems. Extremely low flow rates and potentially higher pressures could pose functional and financial challenges when using a traditional flowmeter. An optical sensor system was developed in order to determine chemical flow rates for a direct nozzle injection sprayer. These low-cost sensors utilize an LED and photodiode pair in order to measure the absorbance of a dye mixed with the chemical solution. The sensor system was also capable of handling varying concentrations of dye mixed in with the chemical solution. The sensor system was calibrated, tested, and was able to determine the chemical flow rate with an average error of 2%. A control system was also developed using the optical sensor system as the feedback loop and tuned to be critically damped. The control system was able to maintain the chemical flow rate within ±2% with a total lag time averaging 5 seconds. The optical sensor system was capable of successfully measuring the chemical flow rate and maintaining application rates when used within a control system.

Advisor : Joe D. Luck