Rosemount 848T, Справочное руководство

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Reference Manual
00809-0100-4848, Rev AA
July 2009
Rosemount 848T Wireless
5-2
CALIBRATION
Calibrating the transmitter increases the measurement precision by allowing
corrections to be made to the factory stored characterization curve by digitally
altering the transmitter’s interpretation of the sensor input.
To understand calibration, it is necessary to understand that smart
transmitters operate differently from analog transmitters. An important
difference is that smart transmitters are factory characterized, meaning that
they are shipped with a standard sensor curve stored in the transmitter
firmware. In operation, the transmitter uses this information to produce a
process variable output, in engineering units, dependent on the sensor input.
Perform a sensor trim if the transmitter’s digital value for the sensor
measurement variables does not match the plant’s standard calibration
equipment. The sensor trim function calibrates the sensor to the transmitter in
temperature units or raw units. Unless the site-standard input source is
NIST-traceable, the trim functions will not maintain the NIST-traceability of the
system.
Sensor Trim
To calibrate the transmitter using the sensor trim function:
1. Assemble and power the calibration system including the 848T, Field
Communicator/AMS, power supply, and temperature input source.
2. From the Home Screen, select 3: Service Tools.
3. Select 4: Routine Maintenance.
4.
Select 1 - 4: Calibrate Sensor 1, 2, 3, or 4.
5. Select 5: Lower Sensor Trim.
6. Follow the on-screen instructions to complete the adjustment of the
lower value.
7. Repeat the procedure for the upper value. Select 6: Upper Sensor
Trim and follow the on-screen instructions to complete the adjustment
of the upper value.
8. Verify calibration.
Recall Factory Trim
Recalling factory trim recalls the factory-characterization of the standard
sensor curve stored in the transmitter firmware
1. From the Home Screen, select 3: Service Tools.
2. Select 4: Routine Maintenance.
3. Select 1 - 4: Calibrate Sensor 1, 2, 3, or 4 depending on what
selection is made.
4. Select 7: Recall Factory Trim.
Fast Key
3, 4, 1-4,
Fast Key
3, 4, 1-4, 7