Emerson 3051S Specifications download pdf (Page 102)

Reference Manual

00809-0100-4803, Rev DA

Section 4: Operation and Maintenance

April 2013

Operation and Maintenance

Data flow can be summarized in four major steps:

1. A change in a process variable (DP, P, and/or T) corresponds to a change in the sensor

output (Sensor Signal).

2. The sensor signal is converted to a digital format that is understood by the

microprocessor (Analog-to-Digital Signal Conversion).

3. Corrections and flow calculations are performed in the microprocessor to obtain a

digital representation of the process output variables.

4. The Digital Primary Variable (PV) is converted to an analog value (Digital-to-Analog

Signal Conversion).

4.3.2 Sensor trim overview

Trim the sensors using either sensor or zero trim functions. Trim functions vary in complexity

and are application-dependent. Both trim functions alter the transmitter’s interpretation of the

input signal.

Zero trim

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. Since this correction maintains the slope of the characterization curve, it should not be

used in place of a sensor trim over the full sensor range.

When performing a zero trim with a manifold, refer to “Rosemount 305 and 304 Manifolds” on

page 19.

Note

The transmitter must be within five percent or less of the maximum span of true zero

(zero-based) in order to calibrate with zero trim function.

The transmitter will not allow the user to perform a zero trim on an absolute static pressure

sensor. To correct mounting position effects on the absolute static pressure sensor, perform a

lower sensor trim. The lower sensor trim function provides an offset correction similar to the

zero trim function, but it does not require zero-based input.

Upper and lower sensor trim

Sensor trim is a two-point sensor calibration where two end-point pressures are applied, and all

output is linearized between them. Always adjust the lower sensor trim value first to establish

the correct offset. Adjustment of the upper sensor trim value provides a slope correction to the

characterization curve based on the lower sensor trim value. The trim values allow the user to

optimize performance over a specified measuring range at the calibration temperature.

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Emerson 3051S Specifications Page 102