Standard PDA systems that use three detectors for size measurement can be affected by the trajectory and slit effects which are mainly seen with dense sprays. These effects mainly occur in applications that use refracted light and have droplets larger then the measurement volume, but small particles can also be subject to the slit effect.
Since the intensity of the scattered light signal is also a function of the diameter, the Intensity Validation can be used to help improve the size measurement accuracy. Using this validation, the detected intensity (pedestal amplitude) of each particle is used for validation. By checking the signal from each particle against upper and lower bounds using the square law relation, erroneous data due to reflected light being processed as refracted light can be invalidated and rejected from trajectory effect or slit effect.