Determining Necessary Sensor Trims; Sensor Trim Overview - Emerson Rosemount WPG Reference Manual

Operation and Maintenance
March 2016
Table 4-1. Recommended Calibration Tasks
Measurement type
Gage
Compound
Vacuum
Absolute
Note
For devices with absolute measurement type, an accurate absolute pressure source is
required.
4.3.1

Determining necessary sensor trims

Bench calibrations allow for calibrating the instrument for its desired range of operation.
Straight forward connections to pressure source allow for a full calibration at the planned
operating points. Exercising the device over the desired pressure range allows for
verification of the output value.
change the calibration. It is possible to degrade the performance of the device if a trim is
done improperly or with inaccurate equipment. The device can be set back to factory
settings using the Recall Factory Trim command in
page
For devices that are field installed, the manifolds discussed in
page 12
eliminate any pressure offsets caused by mounting effects (head effect of the oil fill) and
static pressure effects of the process.
Determine the necessary trims with the following steps.
1.
2.
4.3.2

Sensor trim overview

A sensor trim corrects the pressure offset and pressure range to match a pressure standard.
The upper sensor trim corrects the pressure range and the lower sensor trim (zero trim)
corrects the pressure offset. An accurate pressure standard is required for full calibration. A
zero trim can be performed if the process is vented.
28
Tasks
1. Reconfigure parameters if necessary.
2. Zero trim the device to compensate for mounting effects or static pressure
effects.
3. Optional: Perform a sensor trim. (Accurate pressure source required.)
1. Reconfigure parameters if necessary.
2. Perform low trim value section of the sensor trim procedure to correct for
mounting position effects.
3. Optional: Perform a sensor trim if equipment available (accurate absolute
pressure source required), otherwise perform the low trim value section of the
sensor trim procedure.
31.
allow the device to be zeroed using the zero trim function. This field calibration will
Apply pressure.
Check pressure. If the pressure does not match the applied pressure, perform a
digital zero trim. See
"Sensor trim" on page 30
"Recall factory trim—sensor trim" on
"Sensor trim" on page 30.
Reference Manual
00809-0100-4045, Rev AB
discusses how the trim operations
"Manifold operation" on
Operation and Maintenance