Sensor Trim - Emerson Rosemount 4600 Reference Manual

Operation and Maintenance
September 2016
4.2.3 Selecting a trim procedure
To decide which trim procedure to use, you must first determine whether the ana-
log-to-digital section or the digital-to-analog section of the transmitter electronics need
calibration. Refer to
1.
2.
3.
4.
a.
5.
a.
4.3

Sensor trim

Trim the sensor using either full 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 is a single-point adjustment. It is useful for compensating for mounting position
and sealed gauge effects. Since this correction maintains the slope of the characterization
curve, it should not be used in place of a full trim over the full sensor range.
When performing a zero trim, ensure that the transmitter is vented to atmosphere.
Note
Do not perform a zero trim on Rosemount 4600 Absolute Pressure Transmitters. Zero trim
is zero based, and absolute pressure transmitters reference absolute zero. To correct
mounting position effects on a Rosemount 4600 Oil & Gas 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 zero-based input.
Full trim is a two-point sensor calibration where two end-point pressures are applied, and all
output is linearized between them. Always adjust the low trim value first to establish the
correct offset. Adjustment of the high trim value provides a slope correction to the charac-
terization 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.
40
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Figure 4-1 and perform the following procedure:
Connect a pressure source, a Field Communicator or AMS Device Manger, and a
digital readout device to the transmitter.
Establish communication between the transmitter and the Field Communicator.
Apply pressure equal to the upper range point pressure.
Compare the applied pressure to the Process Variable (PV) line on the Field
Communicator Online Menu or the Primary Variables screen in AMS Device
Manger.
If the PV reading does not match the applied pressure (with high-accuracy test
equipment), perform a sensor trim.
Compare the Analog Output (AO) line, on the Field Communicator or AMS Device
Manger, to the digital readout device.
If the AO reading does not match the digital readout device (with high-accuracy
test equipment), perform an output trim.
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