An Optical Device for the Measurement of Droplet Size Spectra in Calm or Low Wind Conditions

Abstract An instrument for measuring the size and concentration of droplets is described. It has the ability to function in calm and low wind conditions. Droplets in the 5–50 μm diameter range are detected optically. The data acquisition and real-time processing systems corresponding to granulometer measurements are presented. Multiple occupation sample volume (MOSV) signals are taken into account in the processing. The error on the measured droplet concentration is less than 10% when the droplet number is less than 300 per cm3. Results of calibration tests of the instrument, as well as industrial wind tunnel and in situ measurements obtained using it, are presented. They show that this device performs satisfactorily for winds up to 10 m s−1.