TOHO ELECTRONICS TTM200 - Manual (Page 95)

48-7009-E 5-25
5.4.2 Self-tuning function
■ What the self-tuning is
• Self-tuning is defined as a function that automatically executes tuning without requiring operator to
provide instructions and corrects the PID constant at the time of operation start (including power-on),
change of setting value or generation of hunting.
• Ensure to execute the self-tuning in a controllable state after the input 1 terminal and output
terminals (such as the power supply for heater) are wired, and the setting temperature (SV) is set.
• Use the self-tuning function when automatic setting of PID parameters are desired after selecting the
PID control {forward operation (cooling)/reverse operation (heating)}, heating cooling PID control
and position proportional control for the control type setting.
• The values are recorded for automatically-set PID parameters for which self-tuning is complete even
when the power turns off.
PID parameters, however, does not change in case that the power turns off during self-tuning.
 Tuning using step response
Self-tuning that uses the step response method starts if the following conditions are met at the time of
starting operation (including power-on) or changing the setting values.
1) Tuning has not been executed for the present setting values. (Tuning was executed for the
previous values.)
2) Deviation > proportional band × 1.25
Available range of step response
Start
temperature
Setting
value
Elapsed time
Temperature
Proportional
band * 1.25
 Tuning due to hunting
Auto-tuning starts when the following conditions are met for hunting generated after the setting values
are reached.
1) Where the range of hunting is greater than the value of [AT sensitivity]/2 and the hunting does not
terminate
AT sensi-
tivity/2
Range of hunting
Setting
value
Elapsed time
Temperature
AT sensi-
tivity/2