Reference, Installation, and Operations Manual

Section 6: Meter operation

3-9000-743 Rev S

June 2013

 

 

 

Read delta volume registers (either the FLOAT registers or the LONG register pairs) in a single Modbus read. If the delta volume registers are read as LONG register pairs, calculate each delta volume as follows:

Equation 6-20 Triggered Delta volume

DeltaVolume = (Overflow ⋅ 1e9) + Lower

where

 

 

DeltaVolume

=

triggered delta volume (forward or reverse, flow-condition or

 

 

base-condition) (m3 or ft3) (TrigDeltaPosVolFlow,

 

 

TrigDeltaNegVolFlow, TrigDeltaPosVolBase,

 

=

TrigDeltaNegVolBase)

Overflow

triggered delta volume overflow integer value (forward or

 

=

reverse, flow-condition or base-condition) (1e9m3 or 1e9ft3)

Lower

triggered delta volume lower integer value (forward or

 

 

reverse, flow-condition or base-condition) (m3 or ft3)

Repeat "PERIODIC LOOP"

6.1.12Energy rate and totals

The Daniel Mark III Ultrasonic Gas Flow Meter meter calculates the energy rate and energy totals (forward and reverse). These calculations requires that the flow-condition pressure and temperature are available (either fixed or optional analog inputs, see Section 6.1.15), the gas property data (composition and heating value) are available (either fixed or optionally read from a GC, see Section 6.1.16), and the AGA8 calculations are performed (internally by the meter or externally with the results written to the meter, see Section 6.1.17).

The energy rate is calculated as shown in Equation 6-22.

Equation 6-21 Energy rate

Q

 

=

Q

 

1MJ

1000dm3

E

Base

HV -----------------

---------------------

 

 

 

1000kJ

1m

3

 

 

 

 

 

 

 

where

 

 

 

 

 

 

 

QE

 

=

energy rate (MJ/h) (EnergyRate)

 

QBase

 

=

base-condition volumetric flow rate (m3/h) (QBase)

HV

 

=

“in-use” heating value (kJ/dm3) (HeatingValueInUse)

The sign of the energy rate indicates the flow direction: a positive value indicates flow in the forward direction, a negative value indicates flow in the reverse direction.

Energy rate and totals

203