User Manual

45
Determining PID Constants (AT, ST, Manual Setup) Section 3-8
Setting the Hysteresis
Operating Procedure Set the hysteresis to 2.0°C.
3-8 Determining PID Constants (AT, ST, Manual Setup)
3-8-1 AT (Auto-tuning)
• When AT is executed, the optimum PID constants for the set point at that
time are set automatically. A method (called the limit cycle method) for
forcibly changing the manipulated variable and finding the characteristics
of the control object is employed.
• To execute AT, specify on (AT execute), and to cancel AT, specify off (AT
cancel).
• AT cannot be executed when control has stopped or during ON/OFF con-
trol.
• The results of AT are reflected in the “proportional band” (P), “integral
time” (I), and “derivative time” (D) parameters in the adjustment level.
AT Operations AT is started when the “AT execute/cancel” parameter is set to ON. During
execution, the “AT execute/cancel” parameter on the No. 1 display flashes.
When AT ends, the “AT execute/cancel” parameter turns OFF, and the No. 1
display stops flashing.
Operation Level
1. Press the O key to move from the operation level to the adjustment level.
2. The “AT execute/cancel” parameter will be displayed in the adjustment
level.
3. Select the “Hysteresis (heating)” parameter by pressing the M key.
4. Press the U and D keys to set the hysteresis (2.0 in this example). Ei-
ther press the M key or wait for at least two seconds after setting the hys-
teresis value to confirm the setting.
5. To return to the operation level, press the O key for at least one second.
C
25
200
P
V
at
off
AT execute/
cancel
hys
1.0
Hysteresis
(heating)
C
hys
2.0
C
at
i
233
C
p
(0
d
40
Adjustment Level
Proportional band
Integral time
Derivative time