Sequoia LISST-100X, Руководство пользователя

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LISST-100X User’s Guide 91
Clean optics end
before acquiring a
background
Because the area surrounding the windows is submerged,
it is important to thoroughly clean and rinse this part of the
instrument before acquiring a background.
Toothbrush, liquid soap and water works well for
cleaning the optical end of the instrument; do not use
abrasive powders, they will scratch optics and destroy
instrument performance.
Avoid Direct
sunlight Direct sunlight should also be avoided when obtaining a
background. The unit is relatively insensitive to sunlight;
however, bright light can increase the noise in the
measurement and give a false background scattering
measurement. It is recommended that the end of the
instrument be shrouded with a dark cloth during the
acquisition of the background. In general, the background
should be taken in conditions that match the deployment
conditions as closely as possible.
The low concentration limit of LISST-100X is very sensitive
to the quality of the background scatterfile. For this reason,
when working in low concentration water, it is very
important that a good background file be obtained with very
clean water. As particle concentrations increase, the
relative signal-to-background noise ratio also increases,
thus reducing the importance of the background
. However,
Background Scatterfiles should always be done before
an experiment.
Plastic bags, Tupperware or clean containers of any kind
can be used to acquire a background. The instrument’s
optics end can be submerged in them vertically, as long as
the optics are completely submerged and there is no
blockage of the windows by bubbles or other objects.
Background scatterfiles should always be obtained
before each data collection.
Optical
Alignment The background scatterfile is the best source of information
on the current health of the LISST-100X. It provides
information on the current functionality of all of the major
systems including laser, ring detector, data collection
electronics, and optical alignment. The LISST-100X is a
sensitive optical device. The laser must be aligned such
that the focused spot is centered on the hole in the center
of the ring detector. If this alignment in not correct the
instrument will not function correctly. The background file
can easily provide the user with information about the
status of the alignment.