Technical data

3.4.1 Average Flow Velocity
The average velocity is calculated as the average sound velocity of the active chords as
shown in the equation below
Average Flow Velocity Equation 3-6:
C
A
vg
=
∑
Act
iveChords
• C
Chord
NumActiveChords
C
Avg
=
Average sound velocity (m/s)
C
Chord
=
Chord average sound velocity (m/s) (SndVelA...SndVelD)
NumActiveChords =
Number of active chords
3.4.2 Average 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 “Re-acquisition”section
below.
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]). A chord proportion value is the ratio of the chord
velocity to the average weighted flow velocity as shown in Equation 3-7 below. The default
indicator is 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 TRUE. The bin data is stored in non-volatile memory.
Chord Proportion Calculation Equation 3-7:
P
ro p
c
hord
=
V
c
hord
V
AvgWtd
Prop
chord
=
chord proportion (dimensionless)
V
chord
=
chord velocity (m/s) (FlowVelA ... FlowVelD)
V
AvgWtd
=
average weighted gas flow velocity (m/s) (AvgWtdFlowVel)
3.4.3 Update chord proportion bin data values
When the meter has operated for a user-specified number of consecutive batches without
any chord failures, the meter updates each chord’s data values for the bin containing the
chord velocity as shown in Equation 3-9 and sets the bin’s default indicator to FALSE.
ThePropUpdtBatches data point, configurable via the Daniel MeterLink Edit/Compare
Flow measurement
20 Daniel 3810 Series Operations Manual