Jun 23, 2021 | Written by Simerjeet Virk
PWM systems are becoming more common on boom sprayers recently and there are increasing number of growers who are first-time users of these systems and need to make nozzle selection decisions for their systems. While nozzle selection for a PWM system is somewhat similar to the nozzle selection process for a sprayer without PWM, there are few additional things that the growers need to consider because of how a PWM system works and regulates flow rate as compared to the sprayer using a standard rate controller.
PWM sprayer: Travel speed fluctuations are common during pesticide applications. On a boom sprayer equipped with a rate controller, target application rate – with changes in travel speed – is maintained by regulating flow rate – which is primarily accomplished by changing spray pressure. This becomes a problem when spray pressure reaches outside the (narrow) operating range and deteriorates the spray pattern and uniformity. To overcome this issue, Pulse Width Modulation (PWM) systems control flow rate by varying the duty cycle (proportion of the time that nozzle is on; see pictures below) whereas the spray pressure stays constant throughout the boom. In short, a PWM sprayer provides a better control over spray pressure while still maintaining target application rate with ground speed changes, thus enabling consistent and accurate spray application. READ MORE