INTRODUCTION
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Manual USZ 08 · EN05 · 2015-06
11
Base correction of the gas meter
Polynomial
The base correction of the meter is performed via a quartic polynomial which reproduces the error
curve.
Error equation:
F
1
= A
-2
v
wr-2
+ A
-1
v
wr-1
+ A
0
+ A
1
v
wr
+ A
2
v
wr2
F
1
=
Deviation of the error curve
(%)
v
wr
=
Weighted flow velocity
corrected
by
Reynolds
number (m/s)
A
n
= Constants
The constants A
n
(n = -2 to n = 2) are calculated from the measured value pairs Error F
1i
and flow
velocity v
wr
. Instead of the constant meter factor K
V
, the corrected meter factor K
Vc
is used for
further calculation.
K
Vc
= K
V
(1+F
1
/100)
Error curve linearization of the gas meter
Polynomial
The error curve linearization is also performed via a quartic polynomial which represents the error
curve of the gas meter.
Error equation:
F
2
= B
-2
Q
m-2
+ B
-1
Q
m-1
+ B
0
+ B
1
Q
m
+ B
2
Q
m2
F
2
=
Deviation of the error curve
(%)
Q
m
=
Flow rate at measurement conditions
(m
3
/h)
B
n
= Constants
The constants B
n
(n = -2 to n = 2) are calculated from the measured value pairs Error F
2i
and flow
rate Q
mi
. In order to further calculate the corrected flow rate at measurement conditions, the
correction factor of error curve linearization K
c
is used.
K
c
= (1+F
2
/100)