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A zero trim is a single-point adjustment. It is useful for compensating for mounting
position effects, and can be performed with the transmitter installed or from the
bench. 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.
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
HART Fast Keys
To calibrate the sensor 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 main 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
using the zero trim function.
3. Follow the commands provided by the communicator to complete the
adjustment of the zero trim.
Full Trim
HART Fast Keys
To calibrate the sensor using the full trim function, perform the following procedure.
1. Assemble and power the entire calibration system including a transmitter,
communicator, power supply, pressure input source, and readout device.
NOTE
Use a pressure input source that is at least three times more accurate than the
transmitter, and allow the input pressure to stabilize for 10 seconds before entering
any values. If remote seals are used allow more time for the input pressure to
stabilize.
2. From the communicator main menu select 1 Device setup,
2 Diagnostics and service, 3 Calibration, 3 Sensor trim, 2 Lower sensor trim to
prepare to adjust the lower trim point.
1, 2, 3, 3, 1
1, 2, 3, 3
2-10
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