Sequoia LISST-100X, Руководство пользователя

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90 LISST-100X User’s Guide
Performance Optimization
This section contains information on optimizing the
performance of the LISST-100X.
Background
Scatterfile and its
Importance
As was discussed in earlier sections, the LISST-100X uses
a custom detector to measure light scattered at small
angles from particles in water. In order to measure only the
scattered light contributed by the particles, a measurement
of the background scattering must be obtained. This
background scattering can come from a number of areas.
Scratches on the windows, imperfections on the optics, and
other sources all contribute to the scattered light. By
subtracting this background scattering from the measured
data, a true measurement of the light scattered from the
particles can be obtained. The measurement of
background scattering has come to be called a "ZSCAT".
The name comes from the fact that the measurement is
obtained using water with zero "scatterers" or particles.
It is very important that clean and bubble free water is used.
The water can be fresh or salt water. For most
applications, it has been found that steam-distilled water is
sufficient. Steam-distilled water is typically available in one-
gallon containers. We have found that this distilled water
tends to be a bit cleaner than typical bottled or packaged
water. We buy steam-distilled drinking water and filter it
through a 0.2µm filter.
Watch for
outgassing
Another consideration when acquiring a background is
"outgassing" causing small bubbles to form on the
instrument and windows. Bubbles on the windows will
greatly modify the scattering pattern, rendering the
background useless. Be sure to remove any bubbles from
the windows before acquiring a background scatterfile. Use
a squirt bottle or pipette to blow the bubbles off the window.
A small volume horizontal chamber has been provided for
submerging the optics while acquiring a background. It is
inserted between the windows of the optics. The instrument
should be placed horizontally on the supplied white plastic
supports. Roughly 120 milli-liters of water are needed to fill
the chamber.