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NT UF 811 CP GB (e) / June 2015
5) Weighting coefficients of the chords
The chord weighting coefficient is only useful for parallel intrusive probes. It is a correction factor for each
chord applied to the speed before the overall calculation of the flow rate in the pipe from the weighted
speeds of all the chords:
where
C
i
are the weighting coefficients and
Vi
the measured ultrasound speeds.
These coefficients are fundamental for a measurement using parallel chords. They are predetermined
according to the number of chords:
Please feel free to contact Ultraflux to determine the value of the weighting coefficients.
5.6.2 "Linearisation settings" menu
One last action possible on the flow is the linearisation of the result. Depending on the flow, the flow is
corrected by X% based on a pre-defined table:
The parameter Q ref defines the maximum flow used for the linearisation. The points of the table are then
defined as a percentage of this maximum.
The rectifier coefficient must be defined by the user:
- A coefficient of 1 does not change anything in the result.
- A coefficient of 0.8 reduces the value of the flow by 20% at this point, etc.
There are two tables, one for positive flows and one for negative flows.
a / R Ci
2 chords + and – 0.5 0.5
4 chords + and – 0.3090 0.3618
+ and – 0.8090 0.1382