Xylem SonTek FlowTracker2, User Manual

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SonTek – a Xylem brand
FlowTracker2 User’s Manual (January 2019) 224
Principle of Operations Section 13.
13.1. FlowTracker2 Overview
The FlowTracker2 Handheld ADV is a single-point Doppler current meter designed for
field velocity measurements. The FlowTracker2 uses the proven Doppler technology of
the SonTek Acoustic Doppler Velocimeter (ADV), the leading high-resolution velocity
sensor. ADV technology provides several advantages.
•
Accurate velocity measurements in a remote sampling volume,
•
2D or 3D velocity measurements (depending on probe configuration),
•
Invariant factory calibration, no periodic recalibration required,
•
Rapid response time,
•
Simple operation,
•
Excellent performance for low and high flows – accuracy 1% of measured
velocity,
•
Built-in temperature sensor.
The FlowTracker2 offers ADV performance from a simple handheld interface, allowing
rapid data collection without the use of a computer. Some common applications
include:
•
River discharge measurements (using established methodology, including
USGS/ISO),
•
Open-channel flow measurements,
•
Current measurements in large pipes,
•
Rapid, multi-point current surveys,
•
Current monitoring in water treatment facilities.
13.2. The Doppler Shift
The FlowTracker2 uses a highly sophisticated form of this technique, which processes
underwater sound (sonar) reflected from particulate matter suspended in the water.
a) The Doppler principle says that if a source of sound is moving relative to the
receiver, the frequency of the sound at the receiver is shifted from the transmit
frequency.
𝐹
𝑑𝑑𝑑𝑑𝑑𝑑𝑑
= 𝐹
𝑠𝑑𝑠𝑑𝑠𝑑
× �
𝑉
𝐶�
where, F
doppler
= change in received frequency (Doppler shift),
F
source
= frequency of transmitted sound,
V = velocity of source relative to receiver,
C = speed of sound.