Emerson Fisher FIELDVUE DVC6000 Instruction Manual page 85

When a double-acting actuator is used, you will be
prompted to run the Relay Adjustment when Auto
Travel Calibration is selected. Select Yes to adjust the
relay. Select No to proceed with Auto Travel
Calibration. For additional information, refer to Relay
Adjustment in this section.
Select Calibrate, Travel Calibration, Auto Calibration,
then follow the prompts on the Field Communicator
display to automatically calibrate travel.
1. Select the method of crossover adjustment:
manual, last value, or default. Manual is the
recommended choice. If you select Manual, the Field
Communicator will prompt you to adjust the crossover
in step 3.
If you select Last Value, the crossover setting
currently stored in the instrument is used and there
are no further user interactions with the
auto-calibration routine (go to step 6). Use this
selection if you cannot use manual, such as when you
cannot see the valve.
If you select Default, an approximate value for the
crossover is written to the instrument and there are no
further user interactions with the auto-calibration
routine (go to step 6). Use this selection only as a last
resort. Default assumes a midrange position on the
travel sensor as the crossover point, however, this
may not be an appropriate value to use for crossover
because of variations in mounting and travel sensor
calibration.
2. The instrument seeks the high and low drive points
and the minor loop feedback (MLFB) and output bias.
No user interaction is required in this step. For a
description of these actions see step 6.
3. If you select Manual in step 1, you are asked to
select an adjustment source, either analog or digital. If
you use a current source to adjust the crossover,
select Analog and go to step 4. If you wish to adjust
the current source digitally, select Digital and go to
step 5.
4. If you selected Analog as the crossover adjustment
source, the Field Communicator prompts you to adjust
the current source until the feedback arm is 90° to the
actuator stem, as shown in figure 5-1. After you have
made the adjustment, press OK and go to step 6.
5. If you selected Digital as the crossover adjustment
source, the Field Communicator displays a menu to
allow you to adjust the crossover.
Select the direction and size of change required to set
the feedback arm so it is 90° to the actuator stem, as
shown in figure 5-1. Selecting large, medium, and
small adjustments to the crossover causes changes of
September 2013
ACTUATOR
STEM
90_
A6536−3 / IL
Figure 5-1. Crossover Point
approximately 10.0°, 1.0°, and 0.1°, respectively, to
the rotation of the feedback arm.
If another adjustment is required, repeat step 5.
Otherwise, select Done and go to step 6.
6. The remainder of the auto calibration procedure is
automatic.
During calibration, the instrument seeks the high and
low end points and the minor loop feedback (MLFB)
and output bias. By searching for the end points, the
instrument establishes the limits of physical travel, i.e.,
the actual travel 0 and 100% positions. This also
determines how far the relay beam swings to calibrate
the sensitivity of the beam position sensor.
Adjusting the minor loop feedback bias is done around
mid travel. The valve position is briefly moved back
and forth to determine the relay beam position at
quiescence. Essentially, it establishes the zero point
for the Minor Loop Feedback circuit. The back and
forth motion is performed to account for hysteresis.
Adjusting the output bias aligns the travel set point
with the actual travel by computing the drive signal
required to produce 0% error. This is done while the
valve is at 50% travel, making very small adjustments.
Calibration is complete when the "Auto Calibration has
completed" message appears.
7. Place the instrument In Service and verify that the
travel properly tracks the current source.
If the unit does not calibrate, refer to table 5-1 for error
messages and possible remedies.
Calibration
FEEDBACK ARM
5
5-3