67
Determining the PID Constants (AT or Manual Settings) Section 3-8
AT Hysteresis
The AT Hysteresis parameter sets the hysteresis when switching ON and OFF
for the limit cycle operation during auto-tuning.
Limit Cycle MV Amplitude
The Limit Cycle MV Amplitude parameter sets the MV amplitude for limit cycle
operation during auto-tuning.
Note Disabled for 100% AT.
■ 40% AT (at-1)
The width of MV variation in the limit cycle can be changed in the Limit Cycle
MV Amplitude parameter, but the AT execution time may be longer than for
100% AT. The limit cycle timing varies according to whether the deviation (DV)
at the start of auto-tuning execution is less than 10% FS.
■ 100% AT (at-2)
Operation will be as shown in the following diagram, regardless of the devia-
tion (DV) at the start of AT execution. To shorten the AT execution time, select
100% AT.
Note The Limit Cycle MV Amplitude parameter is disabled.
Operating Procedure This procedure executes 100%AT.
SP
PV
AT started
AT ended
Time
Limit Cycle MV
Amplitude 40%
Deviation ≥ 10% FS
Deviation:
10% FS
Time
Deviation < 10% FS
SP
PV
AT started AT ended
Limit Cycle MV
Amplitude 40%
Deviation:
10% FS
SP
PV
AT started AT ended
Time
Limit Cycle MV
Amplitude 100%
Adjustment Level
1. Press the O Key twice to move from the operation level to the adjustment
level.
Press the M Key to select the AT Execute/Cancel parameter.
2. Press the U Key to select at-2. The No. 1 display for AT Execute/Cancel
will flash during AT execution.
3. off will be displayed when AT ends.
at
off
AT Execute/
Cancel
at
at-2
at
off
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