ADS Environmental Services Portable FlowShark Pulse QR 775006 A2 - Manual (Page 37)

2-16 ADS Portable FlowShark Pulse Manual
reflection pattern. Several other factors also influence particle reflection and velocity
profile measurement. Rotating particles may exhibit multiple shapes for reflection;
particles may exit the measurement range before a subsequent measurement can
occur; and new particles may enter into the measurement range.
Conditions at second signal detection
The DSP checks both of the received reflection patterns for similarities using the
cross-correlation method. All unidentifiable signals are rejected so that the two
similar, but temporarily offset, signal patterns remain for velocity evaluation.
The patterns are analyzed within 16 measurement windows established based on the
previous depth levels. The DSP then examines the lag
∆t (change in time – Refer to
t1, t2, and t3 below) of the signal pattern within each measurement window.
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
flow profile indicated on the display reflects the mathematical integration of the
individual velocity measurements. Calculating the individual flow velocities
produces the velocity profile indicated on the unit display.
Investigated flow profile
Flow volume can be calculated based on the flow velocity distribution, pipe shape and
dimensions, and flow depth.
Pipe bottom
Wedge Sensor