January 2017
14
Quick Start Guide
2.6 Trim the transmitter
Devices are calibrated by the factory. Once installed, it is recommended to
perform a zero trim on gage and differential pressure transmitters to eliminate
error due to mounting position or static pressure effects. A zero trim can be
performed using either a Field Communicator or configuration buttons.
For instructions using AMS Device Manager, see the Rosemount 3051 HART
Revision 5 and 7 Reference Manual
.
Note
When performing a zero trim, ensure that the equalization valve is open and all wet legs
are filled to the correct level.
1. Choose your trim procedure.
a. Analog zero trim – Sets the analog output to 4 mA.
Also referred to as a “rerange,” it sets the lower range value (LRV) equal
to the measured pressure.
The display and digital HART output remains unchanged.
b. Digital zero trim – Recalibrates the sensor zero.
The LRV is unaffected. The pressure value will be zero (on display and
HART output). 4 mA point may not be at zero.
This requires that the factory calibrated zero pressure is within a range
of 3% of the URL [0 + 3% ⫻ URL].
Example
URV = 250 inH
2
O
Applied Zero Pressure = + 0.03 ⫻ 250 inH
2
O = + 7.5 inH
2
O (compared to
factory settings) values outside this range will be rejected by the transmitter.
Trimming with a Field Communicator
1. Connect the Field Communicator, see “Connect the wiring and power up” on
page 9 for instructions.
2. Follow the HART menu to perform the desired zero trim.
Trimming with configuration buttons
A zero trim is to be performed using one of the three possible sets of external
configuration buttons located under the top tag.
To access the configuration buttons, loosen the screw and slide the tag on the
top of the transmitter. Confirm the functionality using Figure 10.
It is not recommended to zero an absolute transmitter, Rosemount 3051CA or 3051TA models.
Table 5. Zero Trim Fast Keys
Analog zero (set 4 mA) Digital zero
Fast Key Sequence 3, 4, 2 3, 4, 1, 3
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