FC1: Legally Relevant Functionalities 6
6.2 Gas Quality AFB
The Gas Quality AFB calculates special characteristics of the gas, using
gas quality data, pressure and temperature measurements and taking the
base conditions to be applied into consideration.
The gas quality data can be parameterized as constant values.
Besides, the FC1 can use gas quality data that are actually measured on-
site by a GQ measurement device (e.g. a gas chromatograph):
• The FC1 supports the connection of some specific GQ measure-
ment devices to a serial interface (COM Port) or LAN interface. The
used protocol standard is Modbus, Modbus IP, or a manufacturer-
dependent protocol, respectively. The Basic System is responsible
for the protocol interfacing and makes the gas quality data available
for the
Gas Quality AFB.
•
In addition, the FC1 supports the connection of GQ measurement
devices that are DSfG protocol capable. The FC1 can use the first
COM port of the CPU as DSfG interface; the
DSfG AFB is
responsible for receiving the gas quality data and makes them
available for the
Gas Quality AFB.
In detail, the Gas Quality AFB performs the following tasks:
• Normalization of the gas component vector, if required
• Calculation of conversion factor C (and the interim results
compressibility factors Zm and Zb, K factor) according to
AGA8-92 DC (ISO 12213-2), SGERG-88 (ISO 12213-3),
AGA-NX19 mod, AGA-NX19 mod BR.KOR.3H or
AGA-NX19 GOST, alternatively Zm/Zb = constant
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Depending on the software version, the Gas Quality AFB may offer additional
calculation standards that are not admitted for use in legal metrology. When selecting
the calculation standard, the regulations of the EU type-examination certificate must
be observed.
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