Yokogawa digitalYEWFLO (DY-FF) - Manual (Page 113)

<APPENDIX 6. Enhanced ARITHMETIC (AR) BLOCK>
A6-6
IM 01F06F00-01EN
A6.4.1 Mode Handling
Mode Output
Auto OUT = PRE_OUT
MAN For OUT, the OUT value in the Auto mode just before
change to MAN or O/S is retained.
O/S
In the Manual mode (including O/S), the value of
OUT in the Auto mode just before a change to the
Manual mode is held or the value written to OUT is
output.
If the mode is switched from Manual to Auto, the
value of OUT that is linearly changed with respect to
the value of PRE_OUT for time set by BAL_TIME is
output. The PRE_OUT always indicates the results
of calculation. After elapse of BAL_TIME, OUT =
PRE_OUT is established. Note that if the value
of BAL_TIME is changed during linear change
of the OUT value, it is not refl ected. The value of
BAL_TIME will be refl ected only after the mode is
changed the next time.
FA0604.ai
PRE_OUT
OUT
AUTO MAN AUTO
BAL_TIME
Case of BAL_TIME = 5 sec
The value of OUT is represented by the following
equation.
y
n
= y
n-1
+ (x
n
-y
n-1
) / ( α - n)
α = (T / t
c
) + 1
*: The value of T/tc truncates digits to the right of
the decimal point.
where y : OUT
x
: PRE_OUT
t
c
: period of execution
T : BAL_TIME
n : period
A6.4.2 Status Handling
The setting of INPUT_OPTS is applied to the input
status. When INPUT_OPTS is applied, there are
cases where the PV status becomes “good” even if
the status of main inputs is “uncertain” or the status
of auxiliary inputs is “uncertain” or “bad.”
The PV status is classifi ed by the following:
• If the statuses of two main inputs are both
“good” or anything other than “good”:
Refer to APPENDIX 6.2.1 “Main Inputs”
• If only one of the statuses of two main inputs is
“good”:
• If the status of IN is “good” and that of “IN_
LO” is anything other than “good”
IN > RANGE_LO   The status of IN
applies.
IN ≤ RANGE_LO   Refer to APPENDIX
6.2.1 “Main Inputs”
• If the status of IN is anything other than
“good” and that of “IN_LO” is “good”
IN_LO < RANGE_H  The status of IN_LO
applies.
IN_LO ≥ RANGE_HI  Refer to APPENDIX
6.2.1 “Main Inputs”
The exception is that if RANGE_LO > RANGE_HI,
the PV status is made “Bad. Confi guration Error.”
The input status irrelevant to the computing
equation selected by ARITH_TYPE will be ignored
and does not affect other statuses. The statuses
of outputs (OUT.Status and PRE_OUT.Status) are
interpreted as the status of the worst input among
the statuses of PV and auxiliary inputs (IN_1,
IN_2, and IN_3) to which INPUT_OPTS has been
applied.
Example: If input status and INPUT_OPTS has
been applied
Case 1 Case 2 Case 3
PV Good
IN_1 Uncertain
IN_2 Bad
IN_3 Bad
INPUT_
OPTS
IN_1
Handled as a
“good” input if
its status is
“uncertain.”
No option
IN_2
Handled as a “good” input if its
status is “bad.”
No option
IN_3 No option
ARITH_TYPE
1) Flow compensation (linear) in APPENDIX
6.3.1 “Computing Equations”
OUT.Status Good Uncertain Bad