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Choosing a measuring mode
The external probes may be installed in dierent ways, depending on the number of times the ultrasonic wave reflects o the
pipe wall. There are four programmable types in the device.
«Direct» or «/» mode
«Reflex» or «V» mode
«N» mode «W» mode
Figure11 - Summary of mounting modes
V mode is to be preferred, since it is suitable for use in the majority of cases.
The longer the path, the more eective the measurement principle. (Significant up and downstream transit time dierence).
However, the ultrasonic echo weakens as the distance increases and will therefore be dicult to process. A
compromise must therefore be found between precision and ease of transmitting and receiving the ultrasound waves. This
compromise depends on the application (fluid, wall quality, diameter, etc.).
In practice, multiple reflection modes are reserved for smooth pipes with no clogging or corrosion.
Positioning the probes
Measuring probes must be positioned in such a way as to avoid zones where there is a risk that air bubbles or sediment could
be present.
Figure 12- Asymmetrical hydraulic profile
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