Emerson manual Zero Trim, Rosemount 3051N, Reference Manual

Reference Manual

00809-0100-4808, Rev CA June 2008

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.

20 mA Point	20 mA Point
4 mA Point	4 mA Point

NONZERO-BASED

LEVEL APPLICATION

Zero Trim

HART Comm. 1, 2, 3, 3, 1

ZERO-BASED LEVEL	ZERO-BASED FLOW
APPLICATION	APPLICATION

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.

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.

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.

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