Tokyo Keiki UFL-30, Installation & Operation Manual

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III- 40
III-3-2 Transmission and reflection methods
With ultrasonic flowmeters, depending on the propagation route of the ultrasonic waves, the
measurement methods can be divided into the transmission method (Z method) and the
reflection method (V method) as shown in Fig. 3-2. Since the above explanation of
measurement principles used the transmission method, the reflection method will be
explained here. An advantage of the reflection method is the ability to consistently obtain
correct measurement values even when some flowing components move perpendicular to
the flow direction. These situations include circling flow, etc. However, since the
propagation route of the ultrasonic waves is approximately twice the length of the route with
the transmission method, larger propagation loss occurs.
θ
Transducer P1
Transducer P2
V
L
Z method (transmission)
measurement
θ
V
θ
P2 P1
V method (reflection)
measurement
Measurement
pipe
Fig. 3-2; Measurement Methods
With the reflection method, although the internal diameter is doubled, as shown in the
figure below, the flow rate is the same and the calculation formulas of the transmission
method are applicable. Therefore, d is changed to 2d and the scale factor is cut in half.
Aside from such small changes, the same formulas are generally used.
θ θ
V
Transducer P2 Transducer P1
2L
P2'
θ
Fig. 3-3; Explanatory Diagram for Reflection Method