Velocity Profile 0.2 \ 0.8; Quality Control Warning Messages; Types Of Warning Messages; Table 6:4 - Quality Control Warning Messages - Xylem SonTek FlowTracker2 User Manual

6.1.10

Velocity Profile 0.2 \ 0.8

The Velocity Profile 0.2 \ 0.8 criterion is intended to identify unusual velocity distribution
within the measurement profile. .
a) For an ideal discharge measurement site, the velocity distribution in the
measurement profile should follow 1/6 power-law.
b) The velocity measurements performed at 0.2 time depth and 0.8 time depth are
Velocity
evaluated against expected velocity profile. If any of the following conditions are
Profile
true, this indicates an unusual velocity profile, and the user is given the option to
Evaluate
add a third velocity measurement at 0.6 time depth.
i). The magnitude of the near-surface velocity (0.2 times depth) is less than the
magnitude of the near-bottom velocity (0.8 times depth).
ii). The magnitude of the near-surface velocity (0.2 times depth) is more than two
times the magnitude of the near-bottom velocity (0.8 times depth).
iii). The near-surface velocity (0.2 times depth) and near-bottom velocity (0.8
times depth) show flow in the opposite direction.

6.2. Quality Control Warning Messages

6.2.1

Types of Warning Messages

Quality Control Warning Message is supplied when measured variable exceeds the
expected criteria of each parameter in
warning messages implemented in the Quality Control process are supplied in
The table layout describing the quality control warning messages consist of the following
key components,
a) Warning, the warning supplied when the parameter is exceeded,
b) Reporting, aspect of the measurement process relate to the quality control
warning message,
c) QC Criteria, quality control criteria based on SonTek default values or user
specified.
Warning
Low SNR
Approach
Low SNR
Beam SNRs
Not Similar
Large SNR
Variation
FlowTracker2 User's Manual (January 2019)
Table 6-4 - Quality Control Warning Messages
Reporting QC Criteria
Point
Low SNR
Velocity
Point Approach
Velocity Low SNR
Point SNR
Velocity Threshold
Point SNR
Velocity Variation
Quality Control Parameters. The quality control
Description
SNR below 4 dB
SNR between 4db and 7 dB
Difference in SNR for any 2
beams is > SNR Threshold.
One-second SNR data varies
more than expected during a
measurement. May indicate
underwater interference or a
96
SonTek – a Xylem brand
Table 6:4.
Suggested Action
• Improve SNR
• Improve SNR
• Look for underwater
obstacles; repeat
measurement.
• Check probe operation
• Look for underwater
obstacles; repeat
measurement.
• Look for environmental