User`s manual

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MELSEC-Q
8 I/O CONTROL INSTRUCTIONS
(3) Change rate, upper/lower limiter
Change rate and upper/lower limit checks are performed on a difference between the
temporary MV (T) and manipulated value (MV), and the data and alarm are output after the
limiter processings.
(a) The change rate limiter performs the following operation and outputs the result of the
operation to BB4 and DMLA.
Condition BB4, DMLA Result (T1)
|
T
MV
|
DML 0 T
(T
MV)
DML 1
*1
MV DML
(T
MV) DML 1
*1
MV
DML
*1: When DMLI or ERRI in the alarm detection inhibition (INH) is set to 1, DMLA and BB4 show 0
since the alarm is prohibited.
(b) The upper/lower limiter performs the following operation and outputs the result of the
operation to BB2, BB3, MHA and MLA.
Condition BB3, MLA BB2, MHA MV
T1 MH 0 1
*2
MH
T1 ML 1
*3
0ML
ML T1 MH 0 0 T1
*2: When MHI or ERRI in the alarm detection inhibition (INH) is set to 1, MHA and BB2 show 0 since
the alarm is prohibited.
*3: When MLI or ERRI in the alarm detection inhibition (INH) is set to 1, MLA and BB3 show 0 since
the alarm is prohibited.
(4) Reset windup
If the manipulated value (MV) exceeds the upper/lower limit value, the following operation is
performed to return it to the upper/lower limit value and enable immediate response when the
deviation is inverted.
However, when the integral constant (T1) is 0, the reset windup processing is not performed.
Condition Operation expression
When MHA = 1,
1
T
I
T
MVP (MH T) T
T
I
T
When MLA = 1,
1
T
I
T
MVP (ML T) T
T
I
T