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6.3.1
Beam Check Overview
The FlowTracker2 transmits a pulse of sound, it then receives the return signal to noise
ratio for each of the 2 (or 3) receivers as a function of time following the transmit pulse.
Features in the signal to noise ratio profile verify different aspects of system
performance,
a) The horizontal axis indicates the range from the FlowTracker2 probe (in m).
b) The vertical axis is in signal to noise ratio units called SNR (in dB).
c) Ringing from the transmit pulse appears on the left side of the graph.
d) The location of the sampling volume is indicated by increased signal to noise ratio
in a bell-shaped curve,
i). The sampling volume curve corresponds to the transmit pulse passing through
the focal point of the receivers,
ii). The peak of this curve corresponds to the center of the sampling volume,
iii). The location of the sampling volume varies from probe to probe, but is typically
10-12 cm,
iv). All receivers (2 or 3) should see the peak in the same location, although there
will be variation in the height and shape of the curve.
e) A sharp spike indicates a boundary reflection (if a boundary is within range),
i). If the probe is close to a boundary, a sharp reflection should be seen,
ii). The size and shape of this reflection will vary depending on the nature of the
boundary, its distance from the FlowTracker2 and the acoustic conditions of
the water,
iii). We can estimate the distance from the probe to the boundary by the location
of the boundary reflection.
f) After the boundary reflection, the signal to noise ratio flattens out in the region
where there is no reflected signal from the water,
FlowTracker2 User's Manual (January 2019)
Figure 6:3 - Beam Check
99
SonTek – a Xylem brand
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