62
Determining PID Constants (AT, ST, Manual Setup) Section 3-8
3-8-2 ST (Self-tuning)
ST (self-tuning) is a function that finds PID constants by using step response
tuning (SRT) when Digital Controller operation begins or when the set point is
changed.
Once the PID constants have been calculated, ST is not executed when the
next control operation is started as long as the set point remains unchanged.
ST (self-tuning) is enabled when the ST parameter is set to ON in the initial
setting level.
When the ST function is in operation, be sure to turn the power supply of the
load connected to the control output ON simultaneously with or before starting
Controller operation.
When executing self-tuning, turn ON power for the load (e.g., heater) at the
same time as or before supplying power to the Digital Controller. If power is
turned ON for the Digital Controller before turning ON power for the load, self-
tuning will not be performed properly and optimum control will not be
achieved. ST can be set for standard models only.
Operating Procedure This procedure executes self-tuning (ST).
Note PID Constants
When control characteristics are already known, PID constants can be set
directly to adjust control. PID constants are set in the Proportional Band (P),
Integral Time (I), and Derivative Time (D) parameters, according to the Dis-
play PID Selection parameter setting in the PID setting level. Changing the
Proportional Band (P), Integral Time (I), or Derivative Time (D) parameter set-
tings in the adjustment level changes the settings in these parameters in the
current PID set.
3. off will be displayed when AT ends.
Operation Level
4. To return to the operation level, press the O Key.
at
off
C
25.0
0.0
PV
st
Initial Setting Level
1. Press the O Key for at least three seconds to move from the operation
level to the initial setting level.
2. Select the ST parameter by pressing the M Key.
3. Press the U Key to select on. ON is the default.
Operation Level
4. To return to the operation level, press the O Key for at least one second.
The temperature display flashes during self-tuning (ST) execution.
in-t
5
Input Type
st
on
ST
C
25.0
100.0
PV
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