FC1: Legally Relevant Functionalities 6
Gas meter correction (optional)
The optional gas meter correction of the
Flow Conversion AFB uses up
to 10 calibration points, each of them consisting of the flow rate in m
3
/h and
the related error in percent (%).
The correction factor Cf is calculated for any measured flow rate Q by linear
interpolation between the parameterized calibration points. If Q falls below
the lowest flow of all calibration points, the correction factor obtained for that
flow is retained (no extrapolation). The behavior regarding high flow rates is
similar: Above the highest flow rate of all calibration points, the correction
factor remains at the value obtained for that flow rate.
The EN12405 standard (§ 4.4) prescribes a special behavior of the gas
meter correction below Qmin and above Qmax. Therefore, following addi-
tional rules are applied to comply with EN12405:
• below Qmin (Cf := 1): no gas meter correction is performed
• above Qmax: the correction factor remains at the value obtained at
Qmax.
The calibration points are specified in the gas meter's calibration certificate
and have to be parameterized in the related
Flow Conversion AFB, as
well as the minimum and maximum flow rates Qmin and Qmax.
During operation, for each operating point the gas meter correction is carried
out by applying the calculated correction factor Cf as follows:
Vc = Vm * Cf
Qc= Qm* Cf
where
volume at measurement conditions
Vc = volume at measurement conditions, gas meter correction
flow rate at measurement conditions
Qc = flow rate at measurement conditions, gas meter correction
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