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CHAPTER 4 FUNCTIONS
4
4.18 Self-tuning Function
(a) Conditions for starting ST
Starting ST is executed under the following conditions:
• When the setting mode is shifted to the operation mode (Setting/operation mode instruction (Yn1) is
turned off and on) the first time after the power is turned off and on or after the CPU module is reset and
the reset is cancelled
• When the setting mode is shifted to the operation mode the second time or later after the power is turned
off and on or after the CPU module is reset and the reset is cancelled (only when the temperature process
value (PV) has been stable for two minutes or longer before the mode is shifted)
• When the set value (SV) is changed (only when the temperature process value (PV) before the set value
(SV) change has been stable for two minutes or longer
If the starting ST is started when the temperature process value (PV) is not stable, incorrect PID constants may be
determined. Execute the starting ST after the temperature process value (PV) has been stable for two minutes or longer.