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192 Average weighted gas flow velocity
Section 6: Meter operation Reference, Installation, and Operations Manual
June 2013 3-9000-743 Rev S
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 6-7.
Equation 6-7 Estimating average flow velocity using proportion values
where
For each non-failed chord, the interpolated proportion value used in Equation 6-7 is calculated
as follows:
• if the chord’s velocity is surrounded by trained (average velocity, averageproportion)
data pairs, then the interpolated proportion is the linear interpolation between the two
data pairs
• if the chord’s velocity has a trained (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 no trained (average velocity, averageproportion) data pairs, then the
interpolated proportion is the corresponding bin’s default average proportion value
Re-acquisition
If all active chords fail, then the meter re-enters the Acquisition mode. If the VelHold data point
is set to a value greater than zero, then, while in the Acquisition mode, the meter holds the
average weighted flow velocity to the last good value for up to the VelHold number of batches
before setting the velocity to zero. The VelHold default value is 0.
=
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()
-------------------------------------------------------------
=
V
AvgWtd
est
V
chord
InterpProp
chord