Sensor Input Trim - Emerson Rosemount 644 Reference Manual

Operation and Maintenance
March 2021
5.4

Sensor input trim

The sensor trim command allows for alteration of the transmitter's interpretation of the
input signal. The sensor trim command trims, in engineering (°F, °C, °R, K) or raw (ohms,
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.
Figure 5-1: Trim
5.4.1 Application: Linear offset (single-point trim solution)
Procedure
1. Connect sensor to transmitter. Place sensor in bath between range points.
2. Enter known bath temperature using the Field Communicator.
5.4.2 Application: Linear offset and slope correction (two-
point trim)
Procedure
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.
88
Single-point trim
Transmitter System Curve
Site-Standard Curve
Reference Manual
00809-0200-4728
Two-point trim
Emerson.com/Rosemount