Manual – Starflow Ultrasonic Doppler Instrument
Model 6526
Unidata Manual - 6526 Starflow User Manual Issue 17 01 2020.docx
Page 48
An ideal signal when presented as a
histogram appears as a symmetrical peak.
The x axis represents the velocity in
mm/sec. The y axis indicates the relative
number of times a particular velocity has
been received. The approximate “centre” of
this peak is the value of the velocity we are
looking for, as it will be the mean of all the
echoes received.
As the velocity changes the peak will be
seen to move back and forth along the x
axis.
Note:
The Velocity Trace does not indicate
Flow Direction, only Velocity magnitude. The
width of the peak indicates that a range of
velocities is being measured with each
reading. The narrowest of peaks would be
obtained in the ideal conditions of perfectly
laminar, tranquil flows in water with an even
distribution of reflective particles. These
would still be 50—100 mm/sec wide and
would appear as above.
In fast turbulent water the peak can be 500
mm/sec or more wide because of the range
of velocities present in eddies and swirls.
The following histogram is typical.
