YSI SonTek ADVField, Technical Documentation Manual

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SonTek/YSI
ADVField Software Manual (September 1, 2001) 13
Start Time / Current Time
These times are obtained from the computer’s clock.
Start Time
is the time at which data acquisi-
tion was started (time of first sample).
Current Time
is the time of the last screen update (screen
is updated with each sample, but no more than once per second).
Test Time
This is the total length, in seconds, of the velocity time series collected. It is derived from the
ADV sampling clock rather than from the computer’s clock.
Sample Number
The number of the last velocity sample recorded (if recording is enabled) or displayed (if re-
cording is not enabled).
Vel Range
The current velocity range setting.
Heading / Pitch / Roll
These windows display data from the optional compass/tilt sensor (heading, pitch, and roll). Data
are displayed in degrees and are updated with each sample or, at most, once per second.
Tabular Data
The tabular data display is updated after every sample, or no more than once per second. The
values shown are the result of smoothing the ADV data with a recursive exponential filter with
the time constant specified in the
Filter
selection (see Active Keys below). This filter allows you
to set a time scale for estimating mean velocities from the display during data collection. This fil-
tering process is only used for the tabular data display. It is
not
applied to the graphic display or
to the recorded data.
If the display is paused (see Space Bar below), the smoothed data values are replaced by the un-
filtered ADV data values for the last sample (except for standard deviations, which retain the fil-
tered data).
Vx / Vy / Vz or E / N / Up
These are the smoothed / last values of the three velocity components in units corresponding to
the units system selected in the setup mode (cm/s or ft/s), using the coordinate system specified
in the setup mode (
XYZ
or
ENU
).
SNR1 / SNR2 / SNR3
These are the smoothed / last signal-to-noise ratio (SNR) measured at each of the three receivers.
The values are given in dB.
Corr1 / Corr2 / Corr3
These are the smoothed / last values of the correlation coefficient for each of the three receivers.
The values are given as a percent, where 100 means perfect correlation.
σ
Vx /
σ
Vy /
σ
Vz
These are the standard deviations of the three velocity components within the time scale defined
by the filter time constant. They may be useful as an indicator of turbulence or wave orbital ve-
locities. The units are in cm/s or ft/s, depending upon the setting in the setup mode.