Specifications

Channel Master Operation Manual
page 130 RD Instruments
Sentinel: The model name for a self-contained Workhorse ADCP.
Ship Coordinates: Profile data is reported in an orthogonal coordinate
frame as referenced to the ship (if beam 3 is forward then ship coordinates
are the same as instrument coordinates).
Shiptrack: DOS program to integrate and display Navigator data.
Sidelobes: Peaks in sound intensity generated by a transducer found to the
side of the main lobe.
Sidelobe Contamination: This only need be considered when operating an
ADCP near a boundary (e.g. in shallow water). The beam angle of the
main lobe of an ADCP transducer is 20 or 30º off the vertical, which means
that the distance to the boundary along the ADCP centerline is shorter than
the distance to the boundary along a beam. Because most boundaries will
reflect very strongly (much more strongly than the scatterers), sidelobe
energy can travel the shorter path directly to the surface and thereby include
the “velocity” of the boundary with the velocity measurements taken along
the beams at any longer distance. This potential for interference depends
strictly on the beam angle. An ADCP with a 20º beam angle has the poten-
tial for sidelobe contamination at (distance to the boundary)*cos(20º), or
equivalently, the last 6% of the profile. Note: Sidelobe contamination is not
relevant for DVLs, which specifically look for the bottom.
Software Break: When using radio or acoustic telemetry, it is usually not
possible to send a break signal. Under these circumstances an ADCP can be
configured to recognize a series of keystrokes (i.e. = = =) as a break.
Source: Originator of sound of known frequency, here typically the trans-
ducer of an ADCP.
StreamPro: Model name for ADCP designed for discharge measurement in
shallow waterways.
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Top Discharge: When using an ADCP to measure river discharge, it is not
possible to measure all the way to the surface (due to the blank zone and to
the need to mount the transducers at sufficient depth to remain submerged
with no air entraining past the transducers). In order to get an accurate ap-
proximation of the total discharge, the flow in this area must be estimated
and included, usually by extrapolating the measured velocities to the sur-
face.
Transducer: A device to convert electrical energy into sound waves, and
vice versa.