ADS Environmental Services FlowShark Pulse QR 775004 A1 - Manual (Page 34)

4-4 ADS FlowShark Pulse O&M Manual
particles may exit the measurement range before a subsequent measurement can
occur; and new particles may enter into the measurement range.
Fig. 4-3 Conditions at second signal detection
The DSP checks both of the received reflection patterns for similarities using the
cross-correlation method. All existing signal differences are rejected so that the two
similar, but temporarily offset, signal patterns remain for velocity evaluation.
Based on the depth levels, both patterns are subdivided into 16 measurement
windows. The DSP then examines the lag
∆t (change in time – Refer to t1, t2, and t3
in Figure 4-4) of the signal pattern for each measurement window.
Fig. 4-4 Echo signal images and evaluation
The angle of the beam, the interval between the transmitted signals, and the lag
∆t of
the signal pattern for each measurement window determine the flow velocity. The
profile of the acoustic path indicated on the display reflects the mathematical
integration of the individual velocity measurements.
Fig. 4-5 Investigated flow profile
A 3-dimensional representation of the flow velocity distribution can be rendered from
a velocity profile performed at a location with a known pipe height and geometry
(Figure 4-6).