Evaluation of the Accuracy of PMS Optical Array Probes
Open Access
- 1 June 1998
- journal article
- Published by American Meteorological Society in Journal of Atmospheric and Oceanic Technology
- Vol. 15 (3) , 708-720
- https://doi.org/10.1175/1520-0426(1998)015<0708:eotaop>2.0.co;2
Abstract
This paper considers the theory of diffraction image formation of spherical particles and peculiarities of particle sizing by discrete imaging probes. The diffraction images of spherical water droplets are approximated by Fresnel diffraction by an opaque disc. The approach developed in the paper is applicable to all types of array and matrix imaging probes. The analysis measurement accuracy is performed for the PMS Optical Array Prove (OAP)-2D-C and OAP-2Dgray probes. It is shown that a 25-μm resolution PMS OAP-2D-C probe can both oversize and undersize droplets smaller than approximately 100 μm in diameter, and oversize droplets larger than approximately 100 μm. The errors in droplet sizing increase with decreasing size. The discrete manner of particle image registration also leads to losses of particles with sizes smaller than 100 μm. For the ideal case with zero photodiode response time, these losses reach 70% for 25-μm droplets. A nonzero response time will increase these losses. These findin... Abstract This paper considers the theory of diffraction image formation of spherical particles and peculiarities of particle sizing by discrete imaging probes. The diffraction images of spherical water droplets are approximated by Fresnel diffraction by an opaque disc. The approach developed in the paper is applicable to all types of array and matrix imaging probes. The analysis measurement accuracy is performed for the PMS Optical Array Prove (OAP)-2D-C and OAP-2Dgray probes. It is shown that a 25-μm resolution PMS OAP-2D-C probe can both oversize and undersize droplets smaller than approximately 100 μm in diameter, and oversize droplets larger than approximately 100 μm. The errors in droplet sizing increase with decreasing size. The discrete manner of particle image registration also leads to losses of particles with sizes smaller than 100 μm. For the ideal case with zero photodiode response time, these losses reach 70% for 25-μm droplets. A nonzero response time will increase these losses. These findin...Keywords
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