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Abstract. Precision pesticide spray applications have been achieved with nozzles coupled with pulse width modulated (PWM) solenoid valves in recent years. However, PWM-based nozzles may produce inconsistent droplet size distributions and unstable pressures. The experiment was conducted with ten duty cycles from 10% to 100% at an interval of 10%, and six standard flat fan nozzles (XR8001, XR8002, XR8003, XR8004, XR8005, XR8006) under conditions with and without nozzle operating pressure adjustments to measure droplet size distributions and operating pressures. Under the no-pressure-adjustment condition, the nozzle operating pressure was not adjusted when the duty cycle was changed. Under the pressure-adjustment condition, the nozzle operating pressure was adjusted to maintain at 276 kPa at all duty cycles. Test results showed that under the no-pressure-adjustment condition, nozzle operating pressures increased as duty cycle decreased from 90% to 10%, and the increase magnitudes depended on the nozzle orifice sizes. These pressure increases slightly reduced the droplet sizes.