Siemens 7MF4033 series, User Manual

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On-Line Operation UMSITRPDS3-1
November 2010
6-12
6.2.5 Zero Adjustment (Position Correction)
The zero error resulting from a non-vertical installation position can be easily corrected. This procedure
can be performed locally using the magnetic pushbuttons or remotely using the HART Communicator.
Section 7 Calibration and Maintenance discusses the cause of this zero error.
IMPORTANT
To zero an absolute pressure transmitter, a vacuum must be applied! The zero
adjustment of a ventilated absolute pressure transmitter will cause an erroneous
zero set.
1. Ventilate or evacuate the transmitter.
•
Ventilate for pressure, differential pressure, flow, and flanged level transmitters.
•
Evacuate for absolute transmitters to <0.1% of the measuring span.
2. Select mode 7 by pressing the mode pushbutton.
3. Set zero by simultaneously pressing the ( and ' pushbuttons for 2 seconds; 0.000 will appear in the
display.
4. Press the M pushbutton until no mode number is shown. An output current of 4 mA is generated.
6.2.5.1 Zero-Point Alignment at Absolute Pressure
Performing a position correction to an absolute pressure transmitters may not properly calibrate zero if a
vacuum is not available as the reference pressure. In this case, the three options below are available.
•
Perform a lower sensor alignment using the Communicator.
Carry out a lower sensor alignment at an applied, known and sufficiently stable reference pressure.
2
With this type of alignment, the digital displayed measured value is adjusted. The output current is
relative to this displayed value.
•
Set the current in mode 2 of local operation.
Use the formula below to calculate the current to be set for a known, sufficiently stable reference
pressure. (See the footnote below.)
mA mA
p p
p p
I
zo fso
setpt ref 4 16
) (
) (
+ ∗
−
−
=
In model 2, enter this current with the
( and ' pushbuttons and save the value by pressing the M
pushbutton.
With this setting, the digital displayed value is not changed.
•
Change the value of the start of measurement in mode 5 of local operation:
2
If the applied process pressure is known and sufficiently stable, it can be used instead of the reference pressure.
Enter mode 4, when necessary, and enter an appropriate damping value.