Xylem SonTek FlowTracker2 - Velocity Standard Error; Table 6:3 - ΣV Data Types

SonTek – a Xylem brand
FlowTracker2 User’s Manual (January 2019)
87
g) The SNR checks are re-run (Discharge mode and General mode measurement)
to ensure the warnings are set with the most current data.
h) This criterion can be adjusted or disabled under Quality Control Settings.
SNR is primarily a function of the amount and type of particulate matter in the water.
SNR cannot be immediately converted to sediment concentration, it provides an
excellent qualitative picture of sediment fluctuations and with proper calibration, SNR
can be used to estimate sediment concentration.
Velocity Standard Error 6.1.2
Standard Error of Velocity (σV) is a direct measure of the accuracy of the mean
velocity data.
a) σV can be directly interpreted as the accuracy of the mean velocity.
b) σV is calculated by dividing the standard deviation of one-second samples by the
square root of the number of samples.
c) σV is normally dominated by real variations in the flow and will vary depending on
the measurement environment (see Principle of Operations).
σV Data
Display
d) The σV displayed after a point velocity measurement, station and or stations are
completed in both General and Discharge Modes are supplied in Table 6:3.
Table 6-3 – σV Data Types
Mode
Reporting
Type
Description
Discharge
Review Point
Measurement
σV Point
Measurement
X-component velocity standard error.
Review
Station
Mean Station
σV
The station σV is the mean of the X-
component velocity standard error from each
point velocity measurement.
Discharge
Summary
Mean Section
σV
The discharge summary σV is the mean of all
stations average X-component velocity
standard error.
General
Review Point
Measurement
Beam σV at
Point
Measurement
The point measurement σV for each individual
beam (2 or 3 depending on probe type) at the
point measurement.
Review
Station
Mean Beam
σV at Station
The station σV is the mean for each individual
beam (2 or 3 depending on probe type) of all
point measurements at a station.
General
Summary
Mean σV
The general summary σV is the mean of all
stations average X-component velocity
standard error.
σV Data
Evaluate
e) σV is evaluated against number of quality control criteria and at the end of each
velocity point measurement, the following velocity standard error checks are run