Adjusting Lower Range Value / Oblique Sensor - ABB 261GS Operating Instruction

6.4

Adjusting lower range value / oblique sensor

During installation of the transmitter, zero position shifts may
occur due to the mounting position; these must be corrected.
Possible causes include:
— Transmitter mounting position is different from
recommended vertical mounting position
— Fluids in differential pressure lines or remote seal capillary
tubes can generate additional hydrostatic pressure
IMPORTANT (NOTICE)
The transmitter must have reached its operating
temperature (approx. 5 min. after startup, if the
transmitter has already reached the ambient
temperature) in order to perform the zero shift
correction.
There are two options (variant A or B) for correcting the
4 ... 20 mA output signal directly on the transmitter.
1
Fig. 13:
1 Pushbutton (in hole)
Variant A, with pushbutton in device.
1. Make sure that the measured variable corresponds to the
start value for the measurement process, i.e., that the
pressure that the process exerts on the transmitter is the
level of pressure required to generate a 4 mA output
signal. The pressure must be stable (observe set damping
level).
2. Unscrew the housing cover and press the pushbutton in
the bore hole on the electronic unit (see the following
figure) using a pin with diameter of ≤ 2.5 mm. Hold the
pushbutton down for a maximum of 1 s. The output signal
is set to 4 mA. The span remains unchanged.
3. Screw the housing cover back on.
IMPORTANT (NOTICE)
The lower range value is stored to a failsafe
memory approx. 25 s after you activate the
pushbutton.
M10696
Correction procedure "A" described above does not affect the
physical pressure shown; it only corrects the analog output
signal. For this reason, the analog output signal may differ
from the physical pressure shown on the digital display or the
communication tool.
To avoid this discrepancy, you need to correct the zero
position shift (zero shift) as described under variant "B".
IMPORTANT (NOTICE)
The procedure described in "A" above does not
affect the physical pressure shown; it only
corrects the analog output signal. For this
reason, the analog output signal may differ from
the physical pressure shown on the digital
display or the communication tool.
To avoid this discrepancy, you need to correct
the zero position shift (zero shift) as described
under variant "B".
Variant B, with pushbuttons on the optional LCD indicator.
1. Make sure that the process pressure corresponds to the
atmospheric pressure Pe = 0 (with 261Gx) or a complete
vacuum Pabs = 0 abs (with 261Ax). The pressure must be
stable (observe set damping level).
2. Unscrew the housing cover and select the "Calibrate_Zero
Trim" menu item on the LCD indicator.
3. The correction is made by pressing the
details of menu control, see "Configuration with the LCD
indicator").
4. Where the transmitter mounting position differs from the
nominal position, we recommend that you also
compensate for the temperature-dependent effect of this
mounting position. To do this, select the "Device
Setup_Installation angle" menu item (software version
1.5.0 or higher). This shows the angle at which the
transmitter has been installed.
5. Screw the housing cover back on.
button (for
261Gx, 261Ax | IM/261Gx/Ax-EN Rev. 08 21