5-31
Chapter 5. Functions
• If the two values are close, the PV may not change even if the MV has changed
during AT.
In this case, AT may not end. If this happens, stop AT manually, reset the MV
low and high limits, and then start AT again.
• The number of limit cycles from the start to the end of AT and how long the AT
takes differ depending on the process being controlled.
• If AT always fails, instead of using it, set the PID constants manually.
• The progress of AT can be checked on the operation display.
Operation settings (p.6-1)
• If C26 (heat/cool control ) is set to 0 (not used) or 2 (use (shared PID)), a value
indicating the progress of AT is displayed. It starts with 4 and is decremented
to 0, which means that AT is complete.
If C26 (heat/cool control ) is set to 1 (use (individual PID)), AT starts at 7,
decreases by increments of 1, and finishes at 0.
The AT progress value indicates the number of steps remaining until AT ends.
It does not indicate the time until AT ends.
• Depending on the process being controlled, it may not be possible to obtain
suitable PID constants. In such a case, set the PID constants manually.
• Do not change any settings other than At (AT stop/start selection) while AT is
running.
AT (automatic tuning) stop/start (p.5-12), AT (automatic tuning) (p.5-24)
(for details on AT)
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