Emerson FIELDVUE DVC6200f, Instruction Manual

Page: 163 / 326

OS Function Block
November 2010 151
Table 4-47. OUT_ARRAY Coordinates
BKCAL
_IN_1
BKCAL
_IN_2 BKCAL
_OUT
Action
NI NI NI Not Specified
NI OK OK
BKCAL_OUT limited to X21 low and
X22 high
OK NI OK
BKCAL_OUT limited to X11 and X12
high
IR NI IR
Initialize cascade to value given by
curve X1 vs Y1
IR OK OK
Initialize OUT_1 using internal offset
from Y1
NI IR IR
Initialize cascade to value given by
curve X2 vs Y2
OK IR OK
Initialize OUT_2 using internal offset
from Y2
Note 1: OK means the cascade is closed.
Note 2: Recommend using the average of BKCAL_IN_1 and BKCAL_IN_2, or just SP.
The BKCAL_OUT status shows limited high if an
increase in SP cannot be effectively passed on to
either output because the BKCAL_IN_n of both
outputs indicates that a move in the needed direction
is limited. Similarly, limited low is set if a decrease in
SP cannot be effectively passed on to either output.
The slope of the limited line(s) affects the limit
direction. BKCAL_OUT also shows limit status at the
X extremes X11 and X22.
Initialization is not automatic under all circumstance
because some situations have conflicting needs. In
general, when a control region is in trouble, the
upstream controller is limited so it will not drive further
into that region. When you want to move to the other
active region, you can put the upstream controller into
Man mode and move it, or you can drop the good
downstream block out of Cas mode for one evaluation
cycle and then restore Cas mode. This initializes the
upstream controller to the remaining good region of
control.
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