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10. Appendix A
10.2. Standard Function Blocks
410
Experion PKS Series A Fieldbus Interface Module User's Guide
and repeats per minutes for their tuning constants.
Users can choose which tuning constants they want to
display.
Use the Direct Acting CONTROL_OPTS to define how
a change in PV relative to the SP affects the output.
When Direct Acting is ON, the output increases when
the PV exceeds the SP. When Direct Acting is OFF,
the output decreases when the PV exceeds the SP. Be
sure this option is set correctly and never changed
while in the Automatic mode, since it makes the
difference between positive and negative feedback.
This option setting also affects the calculation of the
limit states for BKCAL_OUT.
This block includes a Feed Forward algorithm. It
accepts a value that is proportional to some
disturbance in the control loop as its FF_VAL input.
The FF_SCALE values convert the FF_VAL to a
percent of output span value. The converted value is
multiplied by the FF_GAIN and added to the target
output of the block's algorithm. If the status of FF_VAL
is Bad, the last usable value will be used to prevent a
bump in the output. When the status returns to Good,
the block adjusts its Integral (RESET) term to maintain
the previous output.
The TRK_VAL input brings in an external value or
uses a constant. The TRK_SCALE values convert the
TRK_VAL to a percent of output span value. If the
CONTROL_OPTS Track Enable selection is true and
TRK_IN_D is true, the converted TRK_VAL replaces
the output (OUT), when the block is in Automatic
(Auto), Cascade (Cas), Remote Cascade (RCas), or
Remote-Out (ROut) mode. The CONTROL_OPTS
Track in Manual selection must be true for this to occur
in Manual mode. If the actual mode is OOS or IMan,
the track request is ignored.
If the TRK_VAL replaces the OUT, its status becomes
Locked Out with Limits set to Constant. The actual
mode goes to LO. The status of BKCAL_OUT,
RCAS_OUT and ROUT_OUT goes to Not Invited (NI),
if not already there.
If the status of TRK_IN_D is Bad, its last usable value
will be maintained and acted upon. If the device
restarts, losing the last usable value, it will be set to
false.
Honeywell
R400
July 2010
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