EB 9527-3 EN
25
Settings
8.3 Checking zero
To check zero, make sure that the pressures
in both measuring chambers are identical at
atmospheric pressure, i.e. the signal at
con-
nector A
or at the
TEST
terminals must be
4 mA at a differential pressure of
∆p = 0 mbar (see Fig. 8).
In hazardous areas, only use an ammeter
approved in accordance with ATEX to mea
-
sure the current at the test connection (TEST).
When gas column correction is selected, you
need to take into account that the gas col-
umns in the measuring lines reduce the dif-
ferential pressure because they act in the op-
posite direction. When the pressures are
identical (
∆
p = 0 mbar) the device indicates
a negative value for the content. An output
signal lower than 4 mA is indicated. In this
case, readjust zero as described below so
that the display shows 0 % = 0000 at
∆
p = 0 mbar. The output signal will change
but remains below 4 mA due to the adjusted
gas column correction.
At ∆p = 0 mbar, the display must indicate
0 % or
0000.
Correction when the tank is empty
Deactivate write protection by setting switch
4
to
OFF
.
Press and hold key until
ZERO
and
X,
0X
mbar are displayed. Current signal I
indicates the current value in mA.
Press key to calibrate zero.
Release key. 0 mbar is indicated on the
display
Current signal I = 4 mA.
Activate write protection by setting switch
4
to
ON
.
Correction when the tank is filled
Zero can also be checked while the system is
running, provided the differential pressure
lines are equipped with shut-off and equaliz-
ing valves. In this case, place the valve block
or equalizing valve in the test position to
achieve identical pressures in both measur-
ing chambers.
1.
Close the shut-off valve in the high-pres-
sure line.
2.
Open the equalizing valve or bypass of
the valve block.
3.
Close the shut-off valve in the low-pres-
sure line.
The valve block is in the test position.
Deactivate write protection by setting switch
4
to
OFF
.
Press and hold key until
ZERO
and
X.X
mbar are displayed. The signal I in-
dicates the current value in mbar.
Press key to calibrate zero.
Release key. 0 mbar is indicated on the
display. Signal I = 4 mA corresponds to
filling level at 0 mbar differential pres-
sure (see note on gas column correction).
NOTICE
!
Note
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