Sequoia LISST-200X, Руководство пользователя

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LISST-
200X User’s Manual
3 LISST-200X Introduction & Quick Start
The quick estimates are based on weighted sum of the net scattered
light. One set of weight factors yields the total volume concentration;
the other yields the area concentration of particles. The volume/area
ratio provides mean diameter, also known as the Sauter Mean
Diameter (SMD). Notably, SMD can be quite different from D
50
in broad
or multi-modal size distribution situations. The SMD output is set to
zero in very clear waters, i.e. when transmission is above 98%,
because the SMD can become erratic when the relative scattering
signal is small. [
For an explanation of this method of SMD derivation,
see: Shaped Focal Plane Detectors for Particle Concentration and
Mean Size Observations ; Agrawal, Y.C. and O.A. Mikkelsen, (2009),
Optics Express, v 17, n 25, pp 23066-23077].
Calculating the
full PSD in real
time Newer LISST-
200X’s, starting with serial number 2131 (and older units
with upgraded circuitry), contain more powerful processors that can do
full PSD processing in real time. The processed data can be stored in
the instrument’s memory, or transmitted through its serial port. This is
especially useful for unattended deployments, such as buoys or remote
moorings, where it is not possible to connect a Windows computer to
the instrument for data offloads. For full details, see Autonomous Real-
time Data Processing on page 52.
Particle Shape
Models
–
Spheres or
Irregular Shape
The multi-angle scattering can be interpreted via inversion as arising
from spherical particles, or from irregularly shaped particles. Provided
software gives you the choice and the resulting PSD files are named
differently to distinguish them. As to which particle model to use, we
suggest that when working with natural waters, use the irregularly
shaped model. The spherical model is appropriate only in exceptional
circumstances. For more details see Appendix F: Particle Shape
Models on page 89.