Commissioning; General Remarks; Zero/Span And Write Protection - ABB 266 DDS Operating Instruction

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6 Commissioning

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.
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.
Only explosion-proof devices or indicators 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.
Analogue and HART Communication models
If the pressure applied falls within the values indicated on the
name plate, the output current will be between 4 and 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 22.5 mA if the range is
overshot (depending on the respective configuration).
Standard setting for normal operation
3 .8 mA / 20 .5 mA
In order to prevent errors in flow rate measurements (266Dxx
and 266Mxx) in the lower range, it is possible to set a "cut off
point" and/or a "lin./sq. root transition point" via the optional
LCD integral displays with keypad or via the graphical user
interface (DTM). Unless otherwise specified, the "lin./sq. root
transition point" is set to 5% and the "cutoff" to 6% of the flow
rate end value by the manufacturer; A current that is < 4 mA or >
20 mA may also indicate that the microprocessor has detected
an internal error. In this case the alarm output can be
configured both via the local LCD with keypad, via an external
Hart hand held terminal (ABB DHH805) or via a DTM based
configuration tool (Asset Vision).
Standard setting for error detection (alarm)
3 .7 mA / 21 mA
The graphical user interface (DTM) or the LCD integral display
(if installed) can be used to diagnose the error.
NOTICE
A brief interruption in the power supply results in
initialization of the electronics (program restarts).
NOTICE
• Lower limit: 3.6 mA (configurable from 3.6 to 4 mA)
• Upper limit: 21 mA (configurable from 20 to 23 mA, limited to
22 mA for HART Safety; apply for electronics release 7.1.15 or
later)
Factory setting: high alarm current (21.0 mA)

Zero/Span and write protection

There is only one push button behind the display. It changes its
function depending on the presence of the display. When the
display is installed, it works as hardware write protection
switch. When the write protection is disabled, and it is kept
pressed for some 1 second, then the write protection becomes
enabled. In the opposite logic, when the write protection is
enabled, and the button is kept pressed, then the write
protection becomes disabled. This enable/disable condition
can be observed/confirmed by looking at the lock symbol
appearing or disappearing on the top line of the display.
Write protection prevents the configuration/modification of
device data from being overwritten by unauthorized users. If
write protection is enabled, both local and remote writings are
refused. The Z (Zero) and S (Span) button cannot be used to set
new range values because their writing is disabled while their
use to enter and navigate into the local easy setup menu for the
read/review of the device parameter setting is still allowed.
However, when write protect is enabled, it is still possible to
read out the configuration data using graphical user interface
or communication tools (DD or FDI based).
Transmitter without display requires the communication tool to
activate write protection.
Figure 17 - Write-protection pushbutton
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