Sequoia LISST-100X, Руководство пользователя

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92 LISST-100X User’s Guide
In order to check the status of an instrument you will need
to open the most current background scatter file, as well as
the factory background scatter file (factory_zsc_SNSN.asc),
where SNSN is the instrument serial number. The files are
space separated and will easily open up in Excel or other
spreadsheets. Once you have opened the files you will see
that they consist of 40 rows and 1 column of data.
The first indicator of an alignment problem is a severe drop
in the currently transmitted laser power (row 33) when
compared to the factory laser power. The laser power and
laser reference values (row 36) will change over time but
they should track together. If the value of the laser
power:laser reference ratio for your current background
measurement is less than 85% of the laser power:laser
reference ratio from the factory background file,
misalignment may be occurring.
The second indictor of misalignment is high value on the
inner rings. The inner rings are shown on the left side of
the background display. The most important rings for
misalignment indication are rings 1-4 in the background
scatter file. As the focused laser starts to move away from
the center of the ring detector it will scatter more light onto
the inner rings. This will cause the inner ring values to be
much higher than the factory values, and is also the reason
for the decrease in transmitted laser power.
It must be noted that low laser power or high inner rings
may not always indicate misalignment. Low laser power
can also occur because the windows or water is dirty or if
there are bubbles on the window. Large particles or
bubbles can cause the inner rings to be higher than factory
values.
All of the other possibilities must be eliminated
before it can be concluded that the instrument is
misaligned.
The transmit optics on the LISST-100X do allow for the
possibility of the user adjusting the alignment. A written
procedure can be provided for this procedure. However, it
is highly recommended that the need for re-alignment be
discussed with a trained Sequoia Scientific technical
service representative before attempting this procedure.