28 Average weighted flow velocity using chord proportions
Section 4: Flow measurement 3410 Series Gas Ultrasonic Meters Operations Manual
January 2018 3-9000-777 Rev E
In the event of a chord failure with at least one operating chord, the meter’s average weighted
flow velocity is estimated as shown in Equation 4-7.
Equation 4-7 Estimating average flow velocity using proportion values
where
For each non-failed chord, the interpolated proportion value used in Equation 4-7 is calculated
as follows:
• if the chord’s velocity is surrounded by non-default (average velocity, average proportion)
data pairs, then the interpolated proportion is the linear interpolation between the two
data pairs
• if the chord’s velocity has a non-default (average velocity, average proportion) data pair
on one side of it but not the other, then the interpolated proportion is the data pair
average proportion
• if there are only default (average velocity, average proportion) data pairs, then the
interpolated proportion is the corresponding bin’s default average proportion value.
= estimated average weighted flow velocity (m/s)
(AvgWtdFlowVel)
= (non-failed) chord velocity (m/s) (FlowVelA ... FlowVelD)
= (non-failed) chord interpolated proportion value
(dimensionless)
V
AvgWtd
est
V
chord
Non Failed–
Chord s()
InterpProp
chord
Non Failed–
Chord s()
----------------------------------------------------------------------------=
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