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

 

 

 

Vchord

 

 

 

Non Failed

VAvgWtd

 

=

Chord(s)

est

------------------------------------------------------------InterpPropchord

 

 

 

 

 

 

 

 

Non Failed

 

 

 

Chord(s)

where

VAvgWtdest

Vchord

InterpPropchord

=estimated average weighted flow velocity (m/s) (AvgWtdFlowVel)

=(non-failed) chord velocity (m/s) (FlowVelA ... FlowVelD)

=(non-failed) chord interpolated proportion value (dimensionless)

For each non-failed chord, the interpolated proportion value used in Equation 6-7is calculated as follows:

if the chord’s velocity is surrounded by trained (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 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, average proportion) 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.

192

Average weighted gas flow velocity