Emerson Rosemount 3144P, Reference Manual

Page: 129 / 236

119
Reference Manual
00809-0100-4021, Rev JA
HART Commissioning
April 2017
HART Commissioning
Figure 3-12. Trim
Application: Linear offset (single-point trim solution)
1. Connect sensor to transmitter. Place sensor in bath between range points.
2. Enter known bath temperature using the Field Communicator.
Application: Linear offset and slope correction (two-point trim
solution)
1. Connect sensor to transmitter. Place sensor in bath at low range point.
2. Enter known bath temperature using the Field Communicator.
3. Repeat at high range point.
3.16.1 Sensor input trim
The Sensor Trim command allows for alteration of the transmitter’s interpretation of the input signal as
shown in
Figure 3-12 on page 119 . The sensor trim 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 trim is suitable for validation procedures or for applications that require
profiling the sensor and transmitter together.
Perform a sensor trim if the transmitter’s 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 the site-standard input source is NIST-traceable, the trim
functions will not maintain the NIST-traceability of your system.
The trim functions should not be confused with the rerange functions. Although the rerange command
matches a sensor input to a 4–20 mA output—as in conventional calibration—it does not affect the
transmitter’s interpretation of the input.
Note
A warning will appear “Set the Control Loop to Manual” (see “Setting the loop to manual” on page 10 ).
Single-point trim Two-point trim
Transmitter system curve
Site-standard curve
HART 5 Fast Keys
3, 4, 4
HART 7 Fast Keys
3, 4, 4
R
e
sistanc
e
(
o
h
m
s)
Temperature
R
e
sistanc
e
(
o
h
m
s)
Temperature