Pulse width modulation sprayers: what we have learnt, correct operation and looking ahead

Published: 1 Apr 2019

What is pulse width modulation?

Pulse width modulation (PWM) is a spraying system where the flow rate is controlled by a pulsing solenoid at each nozzle, unlike a standard spray system that directly controls the overall flow rate. Learn more on page 1 of this factsheet.

Key points

  • Pulse width modulation (PWM) sprayers are continuing to improve with new technology providing more consistent performance, individual section control and turn compensation
  • Constant pressure maintains droplet size and spray quality over a range of speeds
  • Low duty cycle operation can result in poor coverage especially with 10Hz systems
  • Newer systems have high cycle frequency (15/30/100Hz) and combine other standalone spraying systems
  • There are many misconceptions about the effective working speed range, correct nozzle size and determining the correct pre-set pressure
  • When set-up and operated correctly PWM sprayers perform accurately

Frequently asked questions

How many sets of nozzles are needed?

Can my PWM sprayer conform with the new 2,4-D VC spray quality permit requirements?

What is the process for selecting the right nozzle?

What does increasing pre-set pressure do to duty cycle?

Topics covered in this factsheet

  • Duty cycle frequency
  • Duty cycle percentage
  • checking coverage and skips with water-sensitive paper
  • PWM nozzle size selection process
  • Types of PWM nozzles
  • PWM nozzles available for 2,4-D application
  • Can air-induction nozzles be used?
  • Larger droplets with PWM
  • Travel distance, pulse frequency and duty cycle interaction
  • PWM hardware and application accuracy

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Region: National