CHAPTER 3 BASIC OPERATION
E5CK
3–24
Ă• AT (autoĆtuning) cannot be executed while operation is reset or during
ON/OFF control.
Ă• When you execute autoĆtuning, the optimum PID parameters are autoĆ
matically set by forcibly changing the manipulated variable to calculate
the characteristics (called the limit cycle method") of the control target.
During autoĆtuning, time counting is stopped and the AT" LED flashes.
Ă• 40%AT or 100%AT can be selected by the limit cycle of MV change width.
Specify [
] or [ ], respectively, in the AT execute/cancel" paĆ
rameter (level 1 mode).
Ă• During heating and cooling control, only 100%AT can be executed. (So,
[
] (40%AT) is not displayed.)
Ă• To cancel AT execution, specify ĂĂĂ
: AT cancel".
In order to set the limit cycle of MV change width to 40%, select 40%AT
to execute autoĆtuning with fluctuations in the process value kept to a
minimum. However, note that autoĆtuning takes longer to execute
compared with 100%AT.
The timing by which limit cycles are generated varies according to whether
or not the deviation (DV) at the start of AT execution is 10% fullĆscale or less.
Deviation at start of AT
execution y 10% FS
Deviation at start of AT
execution < 10% full-scale
Limit cycle of MV change
width 40%
Limit cycle of MV change
width 40%
Set point Set point
Start of AT
execution
End of AT
execution
Start of AT
execution
End of AT
execution
Time Time
Deviation 10%
full-scale
Deviation 10%
full-scale
In order to set the limit cycle of MV change width to 100%, select 100%AT
to shorten the AT execution time without worrying about fluctuations in
the process value.
Set point
Start of AT
execution
End of AT
x
i
n
Time
Limit cycle of MV
change width 100%
JAuto-tuning
(A.T.)
F 40%AT
F 100%AT
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