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Reference Manual
00809-0100-4808, Rev CA
June 2008
2-17
Rosemount 3051N
When performing a zero trim, ensure that the equalizing valve is open and all
wet legs are filled to the correct levels.
NOTE
Do not perform a zero trim on Rosemount 3051N Absolute pressure
transmitters. A zero trim is zero-based, and absolute pressure transmitters
reference absolute zero. To correct mounting position effects on a Rosemount
3051N Absolute Pressure Transmitter, perform a low trim within the full
sensor trim function. The low trim function provides a “zero” correction similar
to the zero trim function but it does not require the input to be zero-based.
FIGURE 2-8. Typical Zero vs.
Non-zero-Based Application
Illustrations.
A full trim is a two-point sensor calibration where two end-point pressures
are applied, and all output is linearized between them. You should always
adjust the low trim value first to establish the correct offset. Adjustment of the
high trim value provides a slope correction to the characterization curve
based on the low trim value. The factory-established characterization curve is
not changed by this procedure. The trim values allow you to optimize
performance over your specified measuring range at the calibration
temperature.
Zero Trim To calibrate the sensor with a HART Communicator using the Zero Trim
function, perform the following procedure.
1. Vent the transmitter and attach a communicator to the measurement
loop.
2. From the communicator menu select 1 Device setup, 2 Diagnostics
and service, 3 Calibration, 3Sensor trim, 1 Zero trim to prepare to
adjust the zero trim.
NOTE
The transmitter must be within 3% of true zero (zero-based) in order to
calibrate it using the zero trim function.
3. Follow the commands provided by the communicator to complete the
adjustment of the zero trim.
ZERO-BASED FLOW
APPLICATION
ZERO-BASED LEVEL
APPLICATION
NONZERO-BASED
LEVEL APPLICATION
20 mA Point
4 mA Point
20 mA Point
4 mA Point
HART Comm. 1, 2, 3, 3, 1