6-16
Chapter 6. OPERATION
• Auto-tuning can be started by
AT
, external switch inputs and
communications. During auto-tuning, the AT LED blinks.
• If one or more of the following conditions occurs during auto-
tuning, auto-tuning is canceled without PID constants being writ-
ten, and the AT LED goes out.
- Cancel by
AT
- Cancel by external switch input
- Cancel by communications
- Change in mode (shift to MANUAL mode or READY mode)
- Execution of automatic motor valve opening adjustment on 2G
output models
- When variable parameter
A
t
setting is changed to “0”
- When input 1 becomes out-of-range
Handling Precautions
• Auto-tuning will not function properly unless the control target
is connected.
• The time from start to end of auto-tuning varies according to the
control target.
• When auto-tuning is executed, control is stopped, OFF and ON
outputs are switched in the case of relay output and voltage out-
put, and the manipulated variable upper and lower limits of the
currently selected PID set are switched several times in the case
of current output and position proportional output. If this causes
controller trouble, manually set the PID value.
• Sometimes a suitable PID value cannot be obtained depending
on the control target. If this happens, manually set the PID value.
PV
SP
2/3
1/3
1/3
2/3
PV
SP
PV>SP
At start
At SP=PV operation
PV<SP
AT start
Normal end
AT start
Normal end
Time
Time
