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Reference, Installation, and Operations Manual Section 6: Meter operation
3-9000-743 Rev S June 2013
Energy rate and totals 203
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
where
Repeat "P
ERIODIC LOOP"
6.1.12 Energy 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
where
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.
=
triggered delta volume (forward or reverse, flow-condition or
base-condition) (m
3
or ft
3
) (TrigDeltaPosVolFlow,
TrigDeltaNegVolFlow, TrigDeltaPosVolBase,
TrigDeltaNegVolBase)
=
triggered delta volume overflow integer value (forward or
reverse, flow-condition or base-condition) (1e
9
m
3
or 1e
9
ft
3
)
=
triggered delta volume lower integer value (forward or
reverse, flow-condition or base-condition) (m
3
or ft
3
)
=
energy rate (MJ/h) (EnergyRate)
=
base-condition volumetric flow rate (m
3
/h) (QBase)
=
“in-use” heating value (kJ/dm
3
) (HeatingValueInUse)
DeltaVolume Overflow 1e9×()Lower+=
DeltaVolume
Overflow
Lower
Q
E
Q
Base
HV×
1MJ
1000kJ
------------------
1000dm
3
1m
3
----------------------
××=
Q
E
Q
Base
HV