GB-13
D
GB
F
NL
I
E
The accuracy is checked by comparing the flow
rates. The pressure and temperature values of
the unit under test corrected with reference to
the master meter have already been taken into
account here:
F
P
= 100% x (((Q
P
x p
P
x T
N
) / (Q
act,N
x p
N
x
T
P
)) - 1)
The following applies:
T
P
= (273.15 + {t
g
}) K
p
P
= {p
g
} mbar
▷
The curly brackets mean “numerical value of”.
▷
On a nozzle test rig with a known flow rate,
steps
4
and
can be omitted.
▷
The error calculation is based on PTB Testing
Instructions, Volume 29: “Messgeräte für Gas –
Gaszähler” (Measuring instruments for gas – gas
meters), Edition 2003.
RTC test
▷
The climatic conditions must be maintained con-
stant at 22 ± 5°C during the entire test duration.
Temperature changes in 24 hours ≤ 2 K.
▷
Ensure that conditions remain sufficiently stable
during the measurement.
▷
The accuracy of the time count can be verified
with this test.
Acclimatize the unit under test and place next
to the time reference unit.
If necessary, activate the time display on both
units.
Ensure synchronous reading by taking a photo.
4
Observe a min. testing time of 72 hours.
5
Repeat steps
and
.
6
The clock deviation of the unit under test must
not exceed the maximum admissible devia-
tion. Maximum admissible deviation = 5 ppm in
24 hours.
Temperature test
▷
The accuracy of the temperature measurement
can be verified with this test.
▷
The temperature test can only be carried out in
Service mode.
CAUTION
To avoid damage to the meter:
–
Comply with ambient temperature, see
page 14 (Technical data). Deviations from
the permitted ambient temperature will be re-
corded in the error memory.
▷
Temperature measurement accuracy, see page
14 (Technical data).
Install the diaphragm gas meter in a climatic
chamber.
Activate Service mode – see page 5 (Service
Change to the “Cyclic test” menu.
▷
The current gas temperature is displayed.
4
Close the climatic chamber.
5
Select an ambient temperature as a reference
value and bring the climatic chamber to this tem-
perature.
▷
To ensure there is also a uniform temperature
in the meter, we recommend starting the meter
air/gas flow during the temperature adjustment
phase.
▷
Ensure that temperature distribution remains
uniform and stable during the temperature
measurement.
6
Compare the measured value to the temperature
reference value.
▷
If required, several reference values can be
checked. In this case, repeat the test as of
point
5
.
Pressure test
▷
The accuracy of the pressure measurement can
be verified with this test.
▷
The pressure test can only be carried out in
Service mode.
CAUTION
To avoid damage to the meter:
– Comply with the maximum allowable operating
pressure, see page 15 (Technical data). Devia-
tions from the permitted operating pressure will
be recorded in the error memory.
▷
Pressure measurement accuracy, see page
▷
Keep the meter a sufficient time under stable
conditions to ensure acclimatization.
▷
Ensure stable conditions (temperature and pres-
sure) during testing.
Close off the meter outlet connector so that it
is leak-tight, preferably with a valve to permit
venting.
Install a closed system with pressure pump and
reference pressure gauge at the inlet.
Slowly increase the pressure with the pressure
pump to the desired pressure.
4
Activate Service mode, see page 5 (Service
5
Change to the “Pressure” menu.
▷
The current pressure inside the meter housing
is displayed as absolute pressure.
6
Apply at least 5 minutes waiting time to ensure
pressure stabilization.
7
Compare the measured pressure value to the
pressure reference value.
8
Slowly open the outlet using the valve to prevent
meter damage.
