A Output Trim Or Scaled Output Trim; 5Output Trim - Emerson Rosemount Reference Manual

Section 3: HART commissioning
April 2014
The following input constants, included with specially-ordered Rosemount temperature
sensors, are required:
R = Resistance at Ice Point
0
Alpha = Sensor Specific Constant
Beta = Sensor Specific Constant
Delta = Sensor Specific Constant
Other sensor may have "A, B, or C" values for constants.
Note
When the Transmitter-Sensor Matching is disabled, the transmitter reverts to factory trim input.
Make certain the transmitter engineering units default correctly before placing the transmitter
into service.
3.15.4 D/A output trim or scaled output trim
Perform a D/A output trim (scaled output trim) if the digital value for the primary variable
matches the plant standard, but the transmitter's analog output does not match the digital
value on the output device (such as the ampmeter). The output trim function calibrates the
transmitter analog output to a 4–20 mA reference scale; the scaled output trim function
calibrates to a user-selectable reference scale. To determine the need for an output trim or a
scaled output trim, perform a loop test (see
Figure 3-12. Dynamics of Smart Temperature Measurement
3.15.5 Output trim
HART 5 Fast Keys
HART 7 Fast Keys
The D/A Trim command allows the user to alter the transmitter's conversion of the input signal
to a 4–20 mA output (see
regular intervals to maintain measurement precision. To perform a digital-to-analog trim,
perform the following procedure with the Traditional Fast Key sequence.
132
Transmitter Electronics Module
Analog-to-Digital
Signal Conversion
Sensor and Ohm/mV
Trim adjust the signal here
Analog
Field
Input
Communicator
3, 4, 5, 1
3, 4, 5, 1
Figure 3-12 on page
"Loop test" on page
Digital-to-Analog
Microprocessor
Signal Conversion
Output and Scaled Output
Trim adjust the signal here
HART
Analog
Output
Output
132). Calibrate the analog output signal at
Reference Manual
00809-0100-4021, Rev GC
98).
HART® commissioning