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Reference Manual
00809-0100-4021, Rev DA
November 2004
3-29
Rosemount 3144P
HART
Figure 3-6. Trim
.
Sensor Input Trim The Sensor Trim command allows the user to digitally alter the transmitter’s
interpretation of the input signal as shown in Figure 3-6 on page 3-29. 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 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 the site-standard input source is NIST-traceable, the trim
functions will not maintain the NIST-traceability of your system
To perform a sensor trim, use the following procedure:
Single Sensor Trim
1. Connect the sensor or calibrator device to the transmitter.
2. Connect the communicator to the transmitter loop.
3. From the Home screen, select 1 Device Setup, 2 Diag/Service,
2 Calibration, 1Sensor Trim, 1 Sensor Inp Trim to prepare to trim the
sensor. Select 1 Sensor 1.
4. Select Sensor 1.
NOTE
A warning will appear reminding the user to Set the Control Loop to Manual”
(see “Setting the Loop to Manual” on page 2-2.)
5. The communicator will ask “Are you using an active calibrator?”
Application: Linear Offset Application: Linear Offset and Slope Correction
Solution: Single-Point Trim Solution: Two-Point Trim
Method:
1. Connect sensor to transmitter. Place
sensor in bath between range points.
2. Enter known bath temperature using
the 375 Field Communicator.
Method:
1. Connect sensor to transmitter. Place
sensor in bath at low range point.
2. Enter known bath temperature using the
375 Field Communicator.
3. Repeat at high range point.
One-Point Trim Two-Point Trim
Transmitter System Curve
Site-Standard Curve
Resistance (ohms)
Temperature
Resistance (ohms)
Tem
p
erature
HART Fast Keys 1, 2, 2, 1, 1