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Reference Manual
00809-0100-4027, Rev AA
December 2005
Rosemount 4500
www.rosemount.com
Section 4 Operation and Maintenance
Calibration for HART Protocol . . . . . . . . . . . . . . . . . . . . . . page 4-1
OVERVIEW This section contains information on commissioning and operating 4500
Pressure Transmitters. Tasks that should be performed on the bench prior to
installation are explained in this section.
HART Communicator and AMS instructions are given to perform configuration
functions. For convenience, HART Communicator fast key sequences are
labeled “Fast Keys” for each software function below the appropriate
headings.
CALIBRATION FOR
HART PROTOCOL
Calibrating a 4500 transmitter may include the following procedures:
• Rerange: Sets the 4 and 20 mA points at required pressures.
• Sensor Trim: Adjusts the position of the factory characterization curve
to optimize performance over a specified pressure range, or to adjust
for mounting effects.
• Analog Output Trim: Adjusts the analog output to match the plant
standard or the control loop.
The 4500 Transmitter uses a microprocessor that contains information about
the sensor’s specific characteristics in response to pressure and temperature
inputs. A smart transmitter compensates for these sensor variations. The
process of generating the sensor performance profile is called factory
characterization. Factory characterization also provides the ability to readjust
the 4 and 20 mA points without applying pressure to the transmitter.
Trim and rerange functions are also distinct and different. Reranging sets the
analog output to the selected upper and lower range points and can be done
with or without an applied pressure. Reranging does not change the factory
characterization curve stored in the microprocessor. Sensor trimming requires
an accurate pressure input and improves compensation by adjusting the
position of the factory characterization curve to optimize performance over a
specific pressure range.
NOTE
Sensor trimming adjusts the position of the factory characterization curve. It is
possible to degrade performance of the transmitter if the trim is done
improperly or with inaccurate equipment.