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c) FlowTracker probes have been tested and have shown negligible flow
interference with the probe as much as 40-50° away from the preferred
alignment. At higher angles, the FlowTracker may see flow interference in the
sampling volume.
Figure 13:6 - Preferred Flow Direction to Avoid Flow Interference
13.11.3
Mounting Correction
Laboratory tow tank tests have indicated the FlowTracker2 probe and mount create flow
disturbance that may have a small impact (approximately 1.0%) on measured velocity
data. The mount is most commonly a top-setting wading rod using an S or J offset
bracket. Additional tests and modeling have looked at whether flowing water shows the
same flow disturbance effect seen in a tow tank (where the FlowTracker2 is towed
through a pool of stationary water).
By default, no correction for flow disturbance is applied to FlowTracker2 data. If you are
using a standard top-setting wading rod, and have decided to apply a correction,
SonTek typically recommends using a correction of 1.0%. For additional information
about the flow disturbance effect, contact SonTek directly.
To apply a flow disturbance correction, set the
Collection Settings menu.
13.11.3.1
No Correction
• With the default setting of No Correction, the FlowTracker2 velocity data is used
directly without any correction for flow disturbance.
13.11.3.2
Custom Correction
• This is selected when you want to apply a correction to account for flow
disturbance from the FlowTracker mount. With this option, you must specify the
value of the Mounting Correction within the range -5% to +5%.
• When applied, the most common value for a standard top setting wading rod is
1.0%. A 1.0% correction means that measured velocity data is increased by 1.0%
to account for the effect of flow disturbance from the wading rod.
FlowTracker2 User's Manual (January 2019)
SonTek – a Xylem brand
Mounting Correction
from the Data
234
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