Yokogawa AXFA14G/C - Manual (Page 80)

IM 01E20F02-01E A-21
APPENDIX 3. ARITHMETIC (AR) BLOCK
A3.4.1 Mode Handling
TA0303.EPS
Auto
MAN
O/S
Mode Output
OUT = PRE_OUT
For OUT, the OUT value in the Auto mode just
before change to MAN or O/S is retained.
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 reflected. The value of
BAL_TIME will be reflected only after the mode is
changed the next time.
FA0304.EPS
PRE_OUT PRE_OUT
OUT
OUT
AUTO AUTO MAN MAN AUTO AUTO
BAL_TIME 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
) / (
␣ - n)
␣ = (T / tc) + 1
*: The value of T/tc truncates digits to the right of the
decimal point.
where y: OUT
x: PRE_OUT
tc: period of execution
T: BAL_TIME
n: period
A3.4.2 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 classified by the following:
· If the statuses of two main inputs are both “good” or
anything other than “good”:
See A3.2.1, 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
Ϲ RANGE_LO → See A3.2.1, 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
м RANGE_HI → See A3.2.1, Main
Inputs
The exception is that if RANGE_LO > RANGE_HI,
the PV status is made “Bad. Configuration 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:
Good PV
Uncertain IN_1
Bad IN_2
Bad IN_3
ARITH_TYPE
Good Uncertain Bad OUT.Status
INPUT_OPTS
IN_1
IN_2
IN_3
TA0304.EPS
Case 1 Case 2 Case 3
Handled as a
“good” input if
its status is
“uncertain.”
No option
No option
No option
Handled as a “good” input if its
status is “bad.”
1) Flow compensation (linear) in A3.3.1,
“Computing Equations”