Installation, operating and maintenance manual
UNIGAS 300
DDG6004MHGB/08-2017/Rev.A2 Software version from M 1.3.40 and D 2.3.37
51
12 Correction of gas meter measuring error
When the gas meter has been calibrated and the calibration data of the gas meter measurement error are
known, then, according to EN12405-1 +A2 (clause 4.4) the gas meter readings may be corrected by an
electronic gas volume converter on the basis of a number of checkpoints at which the meter measuring error
has been determined. The number of checkpoints may vary per gas meter.
A maximum of ten checkpoints can be programmed in UNIGAS 300 for correction of the gas meter measuring
error.
The UNITOOL software can be used to configure the gas meter checkpoints in UNIGAS 300 with the
connected correction values.
On the basis of linear interpolation and the current flow rate, UNIGAS 300 carries out the correction according
to the following formula:
Vc1 = Vm1 x Cf
As the gas meter measuring error at the checkpoints is expressed in %, this error must be converted into the
connected Cf value for each point.
Cf = ____100____
measuring error + 100
Where:
Measuring error = listed gas meter measuring error expressed in %
Example: a measuring error of + 2 % will result in Cf = 0.9804
UNIGAS 300 carries out the measuring error correction under the following conditions:
•
correction will only take place at an impulse frequency of more than ten impulses/s and/or a flow rate
Q >= Q
min
the gas meter. Otherwise Cf=1
•
correction takes place on the basis of linear interpolation between Q
min
and Q
max
of the gas meter
•
if Q > Q
max
of the gas meter, than Cf = Cf for Q
max.
The checkpoints are programmed sequentially in UNIGAS 300 while:
•
the first point Q1 – C1 always matches the measuring error at Q
min
of the gas meter
•
the last point Qn – Cn always matches the measuring error determined at Q
max
of the gas meter
•
the intermediate checkpoints are in the order of increasing Q
•
if less than ten checkpoints are available, the remaining checkpoints are programmed with Q = 0.
In UNIGAS 300 the sequence is not checked when other checkpoints are entered. This is left to the
authority of the verification officer.
UNIGAS 300 does check the range of the values:
Q: 0 – 10,000 m
3
/h
C: 0.9000 – 1.1000
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