Справочник Пользователя для Emerson Process Management 3420
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:
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
L
OOP
"
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,
(forward and reverse). These calculations requires that the flow-condition pressure and
temperature are available (either fixed or optional analog inputs,
), the gas
property data (composition and heating value) are available (either fixed or optionally read from
a GC,
a GC,
), and the AGA8 calculations are performed (internally by the meter or
externally with the results written to the meter,
).
.
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.
forward direction, a negative value indicates flow in the reverse direction.
=
triggered delta volume (forward or reverse, flow-condition or
base-condition) (m
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
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
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