Synonyms: 
Precipitation Size

Cloud, Aerosol, and Precipitation Spectrometer

The CAPS is a combination probe designed around the newest technologies and the experience gained with over 20 years of using similar probes. It meets the goals of measuring a large range of particle sizes--0.5μm to 1.55mm--with one probe, thus minimizing space, cable connections, and data systems necessary for measurement of this range. Today's technology also provides the CAPS the processing power necessary to perform at speeds up to 200m/s. An intuitive graphical user interface, the Particle Analysis and Collection System (PACS), at the host computer, provides simple but powerful control of measurement parameters, while simultaneously displaying on-the-fly size distributions and derived parameters. All data interfaces are done via line drivers meeting the RS-422 electrical specification, allowing cable lengths of up to 100 meters--an improvement over RS-232 lines capable of only 15-meter cable lengths.

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2D-S Stereo Probe

The 2D-S Stereo Probe is an optical imaging instrument that obtains stereo cloud particle images and concentrations using linear array shadowing. Two diode laser beams cross at right angles and illuminate two linear 128-photodiode arrays. The lasers are single-mode, temperature-stabilized, fiber-coupled diode lasers operating at 45 mW. The optical paths are arbitrarily labeled the “vertical” and “horizontal” probe channels, but the verticality of each channel actually depends on how the probe is oriented on an aircraft. The imaging optical system is based on a Keplerian telescope design having a (theoretical) primary system magnification of 5X, which results in a theoretical effective size of (42.5 µm + 15 µm)/5 = 11.5 µm. However, actual lenses and arrays have tolerances, so it is preferable to measure the actual effective pixel size by dropping several thousands of glass beads with known diameters through the object plane of the optics system.

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