Emerson Process Management 3051N User Manual

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, 3 Sensor  trim, 1 Zero trim to prepare to 
adjust the zero trim.

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.

HART Comm.

1, 2, 3, 3, 1