Average Weighted Flow Velocity Using Chord Proportions - Emerson Daniel 3410 Series Operation Manual

Section 4: Flow measurement
January 2018
4.4.4

Average weighted flow velocity using chord proportions

In the event of one or more chord failure(s), the meter operation is dependent upon the number
of non-failed chords. If there is at least one operating chord, then the meter uses a velocity
estimation method described in the following paragraphs. If all chords fail, then the meter re-
enters the Acquisition mode as described in the
The meter partitions the velocity range (for forward and reverse flow) into ten consecutive, non-
overlapping "bins" (where the velocity range is as specified via the MeterMaxVel data point).
The meter maintains a set of bins for each active chord where each bin contain three data
values: (1) the chord's average velocity (within the bin's velocity range), (2) the chord's average
proportion value, and (3) an indicator that the value is still the default
(
Is[Fwd/Rev]Prop[A..D]DfltBin[1..10]
to the average weighted flow velocity as shown in
used to determine if a bin's velocity and proportion data values have been updated from their
initialized values. The bins are initialized with the average velocity over the bin's range and
meter-geometry-dependent proportion values. All default indicators are initialized to
bin data is stored in non-volatile memory.
Equation 4-5 Chord proportion calculation
where
Prop
V AvgWtd
26
Prop
chord
= chord proportion (dimensionless)
chord
= chord velocity (m/s) (FlowVelA ... FlowVelD)
V
chord
= average weighted gas flow velocity (m/s) (AvgWtdFlowVel)
3410 Series Gas Ultrasonic Meters Operations Manual
"Re-acquisition"
). A chord proportion value is the ratio of the chord velocity
Equation 4-5
V
chord
= ---------------------------
V AvgWtd
Average weighted flow velocity using chord proportions
3-9000-777 Rev E
section below.
below. The default indicator is
TRUE
. The