73
10. Auto-reset
Auto-reset
is performed to correct the offset at the point at which PV indication is stabilized
within the proportional band during the PD control. Since the corrected value is internally
memorized, it is not necessary to perform the auto-reset
again as long as the process is
the same. However, when proportional band (P) is set to 0 or 0.0, the corrected value is
cleared.
(Fig. 10-1)
11. AT (Auto-tuning)
In order to set each value of P, I, D and ARW automatically, the AT process should be made
to fluctuate to obtain an optimal value. One of 3 types of fluctuation (p.74) is automatically
selected.
For DC voltage, current inputs, the AT process will fluctuate around the SV for conditions of
[1], [2] and [3]. (p.74)
Notice
• Perform AT during the trial run.
• If PID zone function is set to “Used”, perform AT in each PID zone.
In (Fig. 11-1), AT is performing at PID zone value 1 and PID zone value 2.
Step
1
2
3
4
5
(Fig. 11-1)
• If AT is cancelled during this process, each value of P, I, D and ARW reverts to the values
before the AT was performed.
• AT will be forced to stop if it has not been completed within 4 hours.
• During AT, if Direct/Reverse action (003) is switched in [Event input allocation], the AT stops.
• During AT, none of the setting items can be set.
• If power failure occurs during the AT, the tuning stops.
• Sometimes the AT process will not fluctuate if AT is performed at or near room temperature.
Therefore, AT might not finish normally.
Auto-reset is performed.
Offset is corrected.
Offset span
Temperature
Time
SV
PID zone
value 2
PID zone
value 1
PID zone parameters of PID zone
value 1 are calculated by
performing AT.
PID zone parameters of PID zone
value 2 are calculated by
performing AT.
