CONTROLLING CHEMICAL APPLICATION RATE WITH BYPASS SPRAY NOZZLES.

Microprocessor based sprayer control system was developed to regulate chemical application rate according to the soil organic matter content and sprayer ground speed. Bypass nozzles were used to maintain uniform spray characteristics over a wide range of flow rates. The application rate was controlled by regulating the pressure of the bypass line with a pressure relief valve controlled by a step motor. The steady-state and transient responses to various excitation signals were obtained to evaluate the system stability and performance. The control system was stable with less than 5% of steady-state error while achieving a turn down ratio of 5:1 with the bypass nozzles used.