Emerson Rosemount - A Output Trim or Scaled Output Trim; 5 Output Trim

132
Reference Manual
00809-0100-4021, Rev GC
Section 3: HART commissioning
April 2014
HART® commissioning
The following input constants, included with specially-ordered Rosemount temperature
sensors, are required:
R
0
= Resistance at Ice Point
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 “Loop test” on page 98).
Figure 3-12. Dynamics of Smart Temperature Measurement
3.15.5 Output trim
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 Figure 3-12 on page 132). Calibrate the analog output signal at
regular intervals to maintain measurement precision. To perform a digital-to-analog trim,
perform the following procedure with the Traditional Fast Key sequence.
HART 5 Fast Keys
3, 4, 5, 1
HART 7 Fast Keys
3, 4, 5, 1
Microprocessor
Digital-to-Analog
Signal Conversion
Analog-to-Digital
Signal Conversion
Transmitter Electronics Module
Sensor and Ohm/mV
Trim adjust the signal here
Output and Scaled Output
Trim adjust the signal here
Analog
Input
Analog
Output
Field
Communicator
HART
Output