Sequoia LISST-SL, Руководство по эксплуатации

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LISST-SL V2.1
User’s Guide
16
Now, back to Testing your
New Background File
Battery Caution
angle is used to estimate depth, or error in depth]. If the
background was acquired recently, the depth should
show a small value (if the LISST-SL is in the lab, or held
just below water surface in a river).
The sediment concentration is displayed in units of mass
per volume. This display assumes a mass density of 2.65
g/ml. If you believe the mass density to be different, a
correction will need to be applied to your final processed
results.
In field use, the velocity display will fluctuate with the
passage of turbulent eddies, and also due to the
movement of the cable itself. However, unreasonable
fluctuations may be due to bubbles in the pitot tube. See
Appendix B for instructions on how to remove bubbles.
The Mean Size on the display is calculated using a
simplified method and is not an exact match to the data
you will process on your PC after downloading. In
extremely clear waters, this number may be erratic. With
increasing turbidity, this number becomes stable.
Note the display of number of samples saved in the data
file, the filename, the date and local time, the water
temperature, and the state of the battery.
Pump supply voltage and current are displayed in a crude
semi-quantitative way. The purpose of this is to help you
identify if the pump is operating. Do not try to interpret
this display in a quantitative way. Digital data on pump
voltage and current are saved in data files.
To stop data acquisition, the STOP button at bottom right
of the display is pressed.
Testing the New Background File: The idea is that if
you measure non-existing sediments in the same clean
water that you used to get your background, the
concentrations should be small. So, to test your
background, from the MAIN MENU, press the MEASURE
button. If the background file is good, the Concentration
display will show small values, of magnitude 0-3 mg/l.
This means the background is good. In our laboratory,
this number is often much less than 1 mg/l. Large and
unsteady values imply a bad background file (unless, of
course, your water has since become contaminated!).
The TCB is programmed to give you a sound alert when
the battery voltage drops to 21.5V. At this time, there is
about 20 minutes of life left on the battery. If you do not
shut down, the instrument will itself shut down when
battery drops to 20V.