Post, SLConnell, RJHewitt, AJ2018-07-022016-01-150265-1491https://hdl.handle.net/10182/9987Phase Doppler measurement devices (termed PDI, PDA, or PDPA by various manufacturers) have established themselves as an alternative to laser diffraction based measurements for recording spray drop size distributions. In addition, phase Doppler devices also provide information on the droplet velocities using laser Doppler anemometry. This information is useful for initialising computational simulations for spray drift prediction. Further, when the drop size and velocity information are integrated over time, the volume (or mass) flux of the spray can be calculated using the effective cross-sectional area of the phase Doppler probe volume, which is calculated from the known diameter of the laser beam. When the phase Doppler laser is traversed across a spray, it effectively acts as an optical patternator, quickly providing information on the spray mass distribution at different heights, while also providing velocities and drops sizes along the spray width as well. In this work, phase Doppler measurements were taken from a 110-01 flat fan nozzle typical of ground boom sprayers. Spray pressure of 4.1 bars was used. One limitation of the phase Doppler systems that is not discussed often in the literature is their sensitivity to the amplification voltage used on the photo-multiplier tube detector. In general, higher voltage leads to higher measured spray fluxes. The correct value of voltage to use depends on the spray density, and so as a general procedure a calibration must be made for each spray by mechanically measuring the flux at a point in the spray. The measurements of volume median diameter were not as sensitive to the voltage setting as the volume flux measurements. In this work the variability and repeatability of the phase Doppler measurements with different sample sizes is also assessed.pp.309-315en© 2016 The Association of Applied BiologistsPhase-dopplerdrop size measurementsmass fluxrepeatabilitysample sizeConference Contribution - published