SonTek – a Xylem brand
FlowTracker2 User’s Manual (January 2019) 231
d) The averaging time required to determine the true mean velocity at a given
location is a function of the real variations in velocity at that site.
Factors Influencing Accuracy 13.8.3.2
Two factors influence accuracy of FlowTracker2 velocity data – sound speed and probe
geometry.
a) The effect of sound speed is discussed in Sound Speed. With properly specified
salinity data, sound speed errors are negligible (less than 0.25%).
b) Probe geometry is calibrated at the factory for each FlowTracker; no recalibration
is required unless the probe has been physically damaged.
c) The FlowTracker2 calibration procedure is specified to ±1.0% of the measured
velocity.
d) There is no potential for zero offset or zero drift in velocity measurements. There
is no inherent minimum measurable velocity.
e) The FlowTracker2 is very well suited to low-flow applications to less than 1 cm/s
(0.03 ft/s).
Quality Control Data 13.8.4
In addition to velocity, the FlowTracker2 records quality control data with each
measurement station to quickly evaluate velocity data quality. The quality control
parameter details are discussed in Quality Control Parameters, Section 6, Quality
Control.
13.9. Special Considerations
Probe Configurations 13.9.1
Several FlowTracker2 probe configurations are available for different applications (see
Figure 13:4).
Probe mounting 13.9.1.1
a) The probe is mounted from a 1.500m (4.92ft) flexible cable. A 3.500m (11.5ft) or
8.500m (27.9ft) extension cable is available. However, it is not possible to
upgrade an existing system to a different cable length.
b) It is not advised to exceed an overall cable length of 10.000m (32.8ft).
c) The cable is custom built to reduce electronic noise. It should not be modified by
the user.
d) Take care to avoid damage to the cable, as this can affect system operation.
Probe type 13.9.1.2
a) Two probe types are available (see Figure 13:4).
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