NT228B GB2
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3.2
Measurement Principle
As written above, please print out from our CD the NT122 didactic handbook.
Inside is very useful information on this measurement principle, ultrasonic waves
transmission, hydraulic conditions, flow profile and Reynolds Number
The first condition to measure flow is that the fluid can transmit ultrasound at
chosen F: it must not be too viscous or include too much particles o gas bubbles
that create a barrier or disperse the energy.
Contrary to the electromagnetic principle, there is no influence of fluid
conductivity.
So, with two probes with following installation:
Always keep in your mind that the flow integration and flow results depend on the
flow section and the flow profile. Choose the best probe arrangement and location
to minimize other influences. Fully developed and stabilized hydraulic conditions
are preferred measurement locations.
The two probes are used alternately as
an emitter and receiver: the difference
between the sound and the flowing fluid
velocities creates a small time difference
between upstream and downstream
sound transmissions.
UF 801-P, with its sophisticated dual 32
bits processors and DSP PC Board,
permits a signal digital shape analyse
and offers a very high resolution and
accurate transit time and Delta t
measurements, the key of high level and
reliable results.
Delta t = t
BA
- t
AB
(nanosecond)
V
US
= (L
2
/2*D)*(
t/t
AB
*t
BA
)
(m/s)
And, with Kh = V
US
/ V
s
(S = section)
Q (Flow) = S * V
us
/ Kh (m
3
/h …)
Volume = Q * Time (m
3
… )
