Few Principles Of Operation - RD Instruments WorkHorse Sentinel User Manual

WorkHorse Sentinel User's Guide
14 A Few Principles of Operation
Consult RDI's Primer (ADCP Principles of Operation: a Practical Primer,
Second Edition for BroadBand ADCPs) to learn more about WorkHorse
principles of operation. The following are a few points from the Primer that
may be worth knowing:
page 38
• Horizontal velocity measurement accuracy is unaffected by
vertical stratification.
• Stratification has negligible affect on the ability of the
WorkHorse to penetrate through the water; concentration of
suspended particles is the main factor influencing profiling
range.
• WorkHorse measurements are automatically corrected for
tilts up to ±20°. In addition to correcting for the beam point-
ing angles, the WorkHorse maps depth cells to other cells at
the same depth.
• If you want to make measurements near the surface from a
bottom-mounted WorkHorse, you should minimize the tilt.
• Depth cells are most sensitive to velocities at the center of
the depth cell and less sensitive at the top and bottom. This
sensitivity is reflected by what we call a 'triangular weight-
ing function'. The details of this weighting function are
rarely important for interpretation and use of your data.
• The actual maximum range can be different from the range
predicted in Plan. Plan corrects for range variations caused
by temperature and salinity, but it assumes typical scattering
conditions. Weak backscatter can sometimes reduce range
by a factor of two or more.
• In self-contained deployments, the maximum profiling range
decreases with time as the battery voltage falls. This is be-
cause transmit power depends on battery voltage. Transmit
power is optimized for about 32 volts. RDI's alkaline battery
packs start at 42 VDC, but spend most of their useful lives
within a few volts of 32 VDC.
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