allows the operator to visualize the cross distribution of the quantity of sand in
the 20 traps. These data are plotted as a stacked bar graph with Traps No. 1
through 20 along the x-axis and the submerged weight of sand along the y-axis.
The height of the 20 bars represents the total submerged weight in each trap. A
color-coded stacked-bar format was used to better visualize the distribution of
weight on the three load cells in a given trap on one plot. Both options for
visualizing the data can be displayed either in real-time or in postprocessing
mode.
To minimize the size of the data files, the data are initially saved in binary
format, and an option in the software can convert data into ASCII format. Two
options for the structure of the ASCII output files are available. The first option
outputs 60 columns of data, each representing the time series for each of the load
cells. These files can be imported directly into a spreadsheet or analyzed using
other programs. However, these output files are usually very large, since the
sample duration can range from 1 to 2 hr in length. The second option outputs
only a summary of the standard statistical parameters that represent the 60
individual time series: average, minimum, maximum, and standard deviation for
each time series. These files are considerably smaller. These statistical
parameters are not very meaningful, however, if they represent the gradual
increase in the quantity of sand in each trap during the experiment. Nonetheless,
they are very useful if, for example, the quantity of sand in each trap was
measured (for say 100 sec at 1 Hz) prior to and immediately after conducting the
experiment, to verify the results obtained during the experiment. Options also
are available for printing of the results. The procedures used for calibration,
measurement, and analysis of these data are discussed in Chapter 8 of this report.
Summary
The LSTF is a complex facility and consists of many different types of
equipment and instrumentation. With respect to real-time control of the
equipment in the LSTF, 14 channels are presently being used; 8 command and
feedback channels for the four wave generators, and 6 command and feedback
channels for the three drive motors on the instrumentation bridge. In addition,
the speed of the 20 vertical turbine pumps is accurately controlled by manually
toggling the human interface module on the front face of each motor controller.
With respect to data acquisition, 132 channels are presently being used; 14 wave
gauge channels, 38 ADV channels, 20 in-line flow sensor channels to measure
the discharge from the 20 pumps, and 60 load cell channels to measure the
quantity of sand in the 20 traps.
The various real-time control systems, data acquisition systems, and analysis
packages discussed in this chapter provide the operator with the capability to
confidently manage all of this equipment and instrumentation, and therefore
conduct a well controlled laboratory experiment in the LSTF. Experience has
shown that all of these systems can be operated simultaneously by two operators.
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Chapter 6
Experiment Control, Data Acquisition, and Analysis Packages
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