Emerson Rosemount 3051 CF Series, Reference Manual

Page: 97 / 146

High trim value
HT = (URV – [S/100
×
P/1000
×
LRV])
Where: HT = Corrected high trim value
URV = Upper range value
S = Span shift per specification (as a percent of reading)
P = Static Line Pressure in psi
In this example:
URV = 1500 inH
2
O (3.74 bar)
S = –0.95%
P = 1200 psi
LT = 1500 – (–0.95%/100 × 1200 psi/1000 psi × 1500 inH
2
O)
LT = 1517.1 inH
2
O
Complete the upper sensor trim procedure as described in Perform a calibration or sensor
trim . However, enter the calculated correct upper sensor trim value of 1517.1 inH
2
O with
a Field Communicator.
5.4 Trim the pressure signal
5.4.1 Sensor trim overview
A sensor trim corrects the pressure offset and pressure range to match a pressure
standard. The upper sensor trim corrects the pressure range and the lower sensor trim
(zero trim) corrects the pressure offset. An accurate pressure standard is required for full
calibration. You can perform a zero trim if the process is vented or the high and low side
pressure are equal (for differential pressure transmitters).
Zero trim is a single-point offset adjustment. It is useful for compensating for mounting
position effects and is most effective when performed with the transmitter installed in its
final mounting position. As this correction maintains the slope of the characterization
curve, do not use it in place of a sensor trim over the full sensor range.
When performing a zero trim, ensure that the equalizing valve is open and all wet legs are
filled to the correct levels. Apply line pressure to the transmitter during a zero trim to
eliminate line pressure errors. Refer to
Manifold operation .
Note
F
OUNDATION
™
Fieldbus has no analog signal that needs ranging. Therefore, ranging a new
device prior to installation is usually not necessary or recommended.
Note
Do not perform a zero trim on Rosemount 3051T Absolute Pressure Transmitters. Zero
trim is zero based, and absolute pressure transmitters reference absolute zero. To correct
mounting position effects on a Rosemount 3051T Absolute Pressure Transmitter, perform
Reference Manual Operation and maintenance
00809-0100-4774 July 2020
Reference Manual 97