ADS Environmental Services FlowShark HV QR 775005 A2 - Manual (Page 19)

ADS FlowShark HV O&M Manual 19
 Poor Reflection Quality in Flow The following histogram displays a very
wide range of frequencies with no stable peak, producing a quality rating of
less than 30%. The velocity readings displayed are essentially too low, and
the histogram suggests that the low quality rating may be the result of a low
concentration of reflective particles that are too small for detection. Scattering
or air-injecting reflective particles, such as sand, into the flow for a short time
could improve the histogram and produce more reliable velocity readings.
Refer to the technical specifications for the sensor for specific information on
the minimum particulate size and concentration required for adequate signal
reflection.
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
Disturbing Influences The following histogram reveals a wide range of
frequences with a random (jumpy) peak that appears in several frequency
groups. The calculated Doppler frequency (F) jumps significantly. Although
the quality is greater than 40%, the velocity readings are erroneous or unstable
and inconsistent. This histogram could reflect the formation of a whirlpool,
standing waves, a turbulent flow surface, or a very shallow flow depth.
Therefore, a site exhibiting these conditions would not be a suitable location
for obtaining reliable velocity measurements.
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