Reference Manual
Rosemount 4500
Section 4 Operation and Maintenance
Calibration for HART Protocol . . . . . . . . . . . . . . . . . . . . . . page
OVERVIEW
CALIBRATION FOR HART PROTOCOL
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.
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.
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