ADS Environmental Services FlowShark HV QR 775005 A2 - Manual (Page 18)

18 ADS FlowShark HV O&M Manual
time period over which the average was calculated will display until a new running
average velocity is initiated or the control unit display is turned off or goes off
automatically.
ADS also recommends an ISO standard that includes several other methods for
calculating average velocity using the individual velocity measurements obtained
through the FlowShark HV:
ISO 748:2007, Hydrometry – Measurement of Liquid Flow in Open Channels Using
Current-Meters or Floats.
Viewing the Results
A velocity frequency histogram shows the distribution of the Doppler frequencies
emitted. Each bar (peak) represents a frequency group, and up to 11 frequency groups
can display at one time. The frequency range is automatically adjusted to fit the range
of the velocities. The distribution and formation of frequency groups in the histogram
indicate the quality of the velocity readings.
The quality of a measurement (ranging from 0 to 100%) represents the correlation
between the evaluated Doppler frequency and the complete spectrum of the measured
frequencies. Typically, higher quality ratings reflect more reliable velocity
measurements. However, occasionally, a velocity measurement with a relatively high
quality can be unreliable. When a measurement is questionable, examine the form of
the frequency distribution. Velocity measurements with a quality of less than 15%
will be rejected. Consider the following sample histograms for reference in assessing
histograms:
 Optimum The following histogram diplays a narrow frequency range with a
stable, very high peak.
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
Normal The following histogram reflects a wide frequency range with a
stable, high peak. It has a quality rating greater than 40%.
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