Ultraflux Uf 811 CO, User Manual, Page: 36 / 106

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NT UF 811 CO GB (c) / March 2014
4) Correspondence between customer reference system and section description reference system
To connect these two reference systems, the elevation must be defined between the zero of the level and
the plane H0.
Three scenarios can be envisaged:
 If the zero level of the water level gauge is below the plane H0, the height of the zero level has a
negative value (see figure above),
 If the plane H0 and the bottom of the water level gauge correspond to the river bed, the height of
the zero level is 0,
 If the plane H0 is defined as being the surface of the water at a reference height of 26m NGF
(General Levelling of France), the height of level zero (therefore 0 NGF) has a value of
-26m since, in the section description, the plane is located at a height of -26m NGF.
Note: The open channel pipe is defined by its section, its hydraulic profile and the position of the ultrasonic
chords.
The number of chords must be determined based on
 the required accuracy
 the amplitude in the variation of the level (since the probes must be submerged in order to operate)
For all of these technical points, consult Ultraflux if necessary.
5.2.2 Number of channels
Note: for multi-channel flow meters only, it is possible to define the number of channels to be managed by
the flow meter. The geometric and physical description of the measuring point must then be produced for
each channel.
In the case of several channels, the channels are named in alphabetical order (A, B, etc.). Qa, Qb, etc. are
the flows calculated for each channel. Qt is the total flow.
Level 0
(customer reference system)
(plane or height H0, Ultraflux
reference system)
Level (water level gauge)
Height of the zero level