ABB 2600T Series Operating Instruction page 20

. . . . CALIBRATION
Zero and span - true zero procedure
Gauge pressure
- Set the A-B switch into "A" position
- Switch on the power supply.
- With no pressure applied to the transmitters, the value read
on the digital milliammeter should be 4 mA ; if it is not turn the
zero screw for at least 1 second. After this operation the
reading should move to 4 mA; if no change occurs repeat the
operation.
- Apply a pressure equal to the upper range value (URV) and
allow time for the pressure to stabilize.
- Turn the span screw for at least 1 second: after this operation
the reading on digital milliammeter should be 20 mA and the
calibration procedure is complete. If no change occurs either
the calibration procedure was not correctly performed or the
span exceeds the limit; correct and repeat the operation.
Absolute pressure
- Set the A-B switch into "B" position
- Switch on the power supply.
- Operate the vacuum pump connected to the transmitter and
draw the maximum possible vacuum obtainable. The value
read on the digital milliammeter should be 4 mA ; if it is not turn
the zero screw for at least 1 second. After this operation the
reading should move to 4 mA; if no change occurs repeat the
operation.
- If the value of the calibration span (URV) is less than
atmospheric pressure gently open the vent valve so increasing
the pressure to the Upper Range Value. If the calibration span
(URV) is greater than the atmospheric pressure then set the A-
B switch to "A" position and generate a pressure corresponding
to the URV. Allow time for the pressure to stabilize.
- Turn the span screw for at least 1 second: after this operation
the reading on digital milliammeter should be 20 mA and the
calibration procedure is complete. If no change occurs the
calibration procedure was not correctly performed or the span
exceeds the limit; correct and repeat the operation.
Zero suppression procedure
Gauge pressure
Two different methods (a) or (b) can be used :
a) After completion of the zero and span procedure above,
apply a pressure equal to the pressure to be suppressed. Allow
time for pressure stabilization and then turn the zero screw for
at least 1 second. After this operation the digital milliammeter
reading should be 4mA and the Upper Range Value
automatically moved to a value equal to the sum of the
pressure to be suppressed and the previous calibrated span.
b) Use the zero and span procedure above but apply pressures
equal to the Lower Range Value (LRV) and then to Upper
Range Value (URV), and turning, for at least 1 second, the zero
and span screws respectively.
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Absolute pressure
Use the zero and span procedure above but apply to the
process connection absolute pressures equal to the Lower
Range Value (LRV) and then to the Upper Range Value (URV),
turning, for at least 1 second, the zero and span screws
respectively.
Zero elevation procedure
This procedure applies to the gauge pressure transmitter, only.
The zero can be elevated up to a full vacuum.
Apply pressures equal to the LRV (this value is therefore
between the zero gauge pressure and the full vacuum) and
then equal to the upper range value (URV) and correspondingly
turn the zero and span screws respectively.
Note - If during the calibration procedure the
readings on the digital milliammeter are outside its
inherent accuracy, output trimming of the transmitter
may be requested. This operation can only be performed
using the Hand Held Terminal Communicator or the
Personal Computer Configurator. If this equipment is
not available the transmitter should be returned to a
Service Center for recalibration.
In some cases, expecially for tank level measurement, the
calibration can also be obtained automatically by the indication
of the actual output percentage, without any calculation for
LRV and URV. The operation is called Output % Reranging
and can be performed using a HART configuration tool (see the
ADDENDUM on Output % Reranging).
WARNING. In order to ensure the correct operation
of the transmitter, after the calibration procedure the
device must be put in "Operating Condition" as described
in Table 1, in the section Commissioning and Configuration
issues.