48
Measures to take if the piping is not filled
completely.
siphon
Sensor 1
Sensor 2
If you cannot separate the piping, because it is plastic
piping, for example, or if the application is in the planning
or installation phase, it is recommended to use a siphon to
compensate for partially filled piping. The gradient of the
siphon is calculated based on the expected flow velocity
and contamination load. Contact GPI for support if it is
necessary to install a siphon for your application.
DIAGNOSTIC MENU
Oscilloscope/Auto-Window
Signal propagation
QStar UFM offers sophisticated diagnostic menus allow-
ing users to optimize challenging measurements in harsh
conditions. To use the diagnostic menu for troubleshoot-
ing, a background in signal propagation is provided.
Figure 63 illustrates which signals occur and how they
progagate at the pipe.
FIGURE 63:
Signal propagation
UP-Transd.
V-Mode
W-Mode
De
sire
d
Pi
pe
S
ig
na
l
V-Mo
de
Signa
l
W-M
ode-
Signa
l
Z-Mode
Z-M
ode
-
Sig
nal
UP-Transd.
V-Mode
W-Mode
De
sire
d
Pi
pe
S
ig
na
l
V-Mo
de
Signa
l
W-M
ode-
Signa
l
Z-Mode
Z-M
ode
-
Sig
nal
UP-Transd.
V-Mode
W-Mode
De
sire
d S
ign
al
Pi
pe
S
ig
na
l
V-Mo
de
Signa
l
W-M
ode-
Signa
l
Z-Mode
Z-M
ode
-
Sig
nal
The UP-transducer mounted at upstream position emits
the send (or desired) signal. This signal propagates within
the pipe wall (“pipe signal”) as well as in the fluid. The
signal propagating in the fluid is reflected a couple of
times at the pipe walls (Z-Mode signal, V-mode signal,
W-mode signal). The signal which represents the desired
signal depends on mounting mode. For example, when
mounted in V-mode the V-mode signal is the desired
signal. The other signals (Z-mode, W-mode, pipe wall)
may also disturb this signal. The corresponding transducer
is mounted in V-mode as standard but Z-mode and W-
modes are possible. This transducer receives the signals
and returns another signal to UP transducer.
The time the signals needs from one transducer to the
corresponding transducer (run time) depends on path
length (distance), speed of sound of materials, fluid and
flow velocity.
Depending on mounting mode the signals might look as
shown in Figure 64.
FIGURE 64:
Signal Images
tp
t1v
t1w
time
Amplitud
e
Se
nd
signal
Pi
pe
S
ig
na
l
V-
M
od
e-
Si
gn
al
W
-M
od
e-
Si
gn
al
tp
t1v
t1w
time
Amplitud
e
Se
nd
signal
Pi
pe
S
ig
na
l
V-
M
od
e-
Si
gn
al
W
-M
od
e-
Si
gn
al
At t=0 the UP-transducer starts signal transmission.
After time T=tp you can see the pipe wall signal which
reaches the corresponding transducer first because of
shorter distance and (usually) faster propagation caused
by higher speed of sound of pipe material.
After that, at time T=t1v, the V-mode signal reaches the
transducer (single reflection at opposite pipe wall). After
t1w (approximately 2x t1p) the W-mode signal is being
detected. Usually, when having pipe materials highly
conductible for ultrasonic signals (metals) and small
pipes, the pipe wall signal has high amplitude which
is similar to amplitude of V-mode signal. When having
sound-absorbing materials (plastic, concrete) and/or
coating the pipe wall signal is usually weak indicated by
low amplitude. The V-mode signal is usually stronger
than the W-mode signal.
The time between the different signals might be signifi
-
cantly higher or lower depending on pipe sizes and speed
of sound of involved materials.
A different situation occurs when measuring in Z-mode.
FIGURE 65:
Signals in Z-mode
tp
t1z
time
Amplitud
e
Se
nd
S
ig
na
l
tp
t1z
time
Amplitud
e
Se
nd
S
ig
na
l
Beside the send signal, only the desired signal (Z-signal)
is visible. The Z-signal reaches the receiving transducer
after T=t1z.