20 IM/261Gx/Ax-EN Rev. 08 | 261Gx, 261Ax
6 Commissioning
6.1 General remarks
Once the pressure transmitter has been installed, it is put into
operation by switching on the operating voltage.
Check the following before switching on the operating voltage:
— Process connections
— Electrical connection
— Fill the impulse line and measuring chamber of the
measuring cell completely with measuring medium.
The transmitter can then be put into operation.
To do this, the shut-off valves must be actuated in the
following order (in the default setting, all valves are closed):
1. Open the discharge shut-off valve, if present.
2. Open the shut-off valve.
To put the transmitter out of operation, carry out the steps in
reverse order.
IMPORTANT (NOTICE)
In the case of pressure transmitters for absolute
pressure and measuring ranges of
≤ 40 kPa absolute, please note that the pressure
measuring cell has been overloaded over a long
period by the atmospheric pressure during
transport and storage. For this reason, you will
need to allow a starting time of approx. 3 hours
after commissioning until the sensor has
stabilized to such an extent that the specified
accuracy can be maintained.
When using transmitters with ‘intrinsic safety’ type of
protection, if an ampere meter is connected to the output
circuit or a modem is connected in parallel while an explosion
hazard is present, the sums of the capacitances and
inductances of all circuits, including the transmitter (see EC
type examination certificate) must be equal to or less than the
permissible capacitances and inductances of the intrinsically
safe signal circuit (see EC type examination certificate for the
power supply unit).
Only passive or explosion-proof test devices or display
instruments may be connected.
If the output signal stabilizes only slowly, it is likely that a large
damping time constant has been set on the transmitter.
6.2 Output signal
If the applied pressure is within the values indicated on the
name plate, the output current ranges between 4 und 20 mA.
If the pressure applied falls outside the set range, the output
current will be between 3.5 mA and 4 mA if the range is
undershot or between 20 mA and 23.6 mA if the range is
overshot (depending on the respective configuration).
Standard setting for normal operation
3.8 mA / 20.5 mA
A current that is < 4 mA or > 20 mA may also indicate that the
microprocessor has detected an internal error.
Standard setting for error detection
21 mA
The graphical user interface (DTM) can be used to diagnose
the error.
IMPORTANT (NOTICE)
A brief interruption in the power supply results in
initialization of the electronics (program restarts).
6.3 Write protection
Write protection prevents the configuration data from being
overwritten by unauthorized users. If write protection is
enabled, the "Lower Range Value / Upper Range Value”
pushbutton will be disabled.
It is still possible to read out the configuration data via optional
LCD indicator, handheld terminal or the graphical user
interface (DTM).
Write protection can be disabled via the graphical user
interface (DTM), a HART handheld terminal, or an optional
LCD indicator (see “Write protection” under “Configuration”).
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