Calibration - Emerson Rosemount 648 Reference Manual

Reference Manual
00809-0200-4648
Figure 2-13: Field Communicator Connections
2.8

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 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.
Calibration of the wireless transmitter may include the following procedures:
Sensor input trim:
Transmitter-sensor
matching:
2.8.1 Sensor input trim
Fast Key sequence
Perform a sensor trim if the transmitters digital value for the primary variable 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 your site-standard
input source is NIST-traceable, the trim functions will not maintain the NIST-traceability of
the system.
The Sensor Input Trim command allows the transmitter's interpretation of the input signal
to be digitally altered. The sensor reference command trims, in engineering (°F, °C,°R, K) or
raw (Ω, mV) units, the combined sensor and transmitter system to a site standard using a
known temperature source. Sensor trimming is suitable for validation procedures or for
applications that require calibrating the sensor and transmitter together.
Rosemount 648 Wireless
1
2
P/N 00753-9200-0020
3
COMM
4
Digitally alter the transmitter's interpretation of the input
signal
Generates a special custom curve to match that specific
sensor curve, as derived from the Callendar-Van Dusen
constants.
3, 5, 2
Configuration
May 2020
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