D/A Output Trim Or Scaled Output Trim - Emerson Rosemount 3144P Reference Manual

Reference Manual
00809-0100-4021, Rev JA
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.
3.16.4

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
page
Figure 3-13. Dynamics of Smart Temperature Measurement
3.16.5 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
maintain measurement precision. To perform a digital-to-analog trim, perform the following procedure
with the traditional Fast Key sequence.
3.16.6 Scaled output trim
HART 5 Fast Keys
HART 7 Fast Keys
The Scaled D/A trim command matches the 4 and 20 mA points to a user-selectable reference scale
other than 4 and 20 mA (2–10 volts, for example). To perform a scaled D/A trim, connect an accurate
reference meter to the transmitter and trim the output signal to scale as outlined in the
procedure.
HART Commissioning
96).
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 3-13 on page
3, 4, 5, 2
3, 4, 5, 2
Digital-to-analog signal
Microprocessor
conversion
Output and scaled output trim
adjust the signal here
HART
Analog
output
output
127). Calibrate the analog output signal at regular intervals to
HART Commissioning
April 2017
"Loop test" on
Output trim
127