IDEC MicroSmart Pentra - Manual (Page 30)

PID M ODULE M AIN F UNCTIONS
FC5A MicroSmart PID Module User’s Manual FC9Y-B1283 4-7
SP+20
SP
AT
Temperature
(4)
Time
(1) (2) (3)
C
SP
Time
Temperature
Offset Span
Offset is Corrected.
Auto-reset is Performed.
[Process variable (PV) ≥ Set point (SP) + AT bias value]
When AT bias is set to 20°C, the PID module starts giving the temperature fluctuation to the process at
the temperature 20°C higher from the set point (SP).
(1) Fluctuation period. PID parameters are
measured.
(2) PID parameters are calculated and auto
tuning (AT) is finished.
(3) Temperature is controlled with the PID
parameters configured with auto-tuning (AT).
(4) AT bias value (20°C)
▲ AT: Auto-tuning (AT) perform bit is turned on
Auto-reset
During the P control or PD control action, the deviation (offset) between the process variable (PV) and the
set point (SP) is generated when the process variable (PV) is stabilized. By performing auto-reset, the reset
value can automatically be calculated to correct the offset. It is required to perform auto-reset when the
process variable (PV) is stabilized within the proportional band. When the auto-reset is completed, the CPU
module automatically reads all parameters including the calculated reset value from the PID module and
stores those parameters in the data registers. It is unnecessary to perform the auto-reset again as long as
the process is unchanged.
When the proportional band (P) is set to 0 or 0.0, the reset value is cleared.
Auto-tuning (AT)/Auto-reset Perform/Cancel
The Auto-tuning (AT)/Auto-reset function can be performed or cancelled by turning on/off the operation
parameter bits allocated to each channel. For the operation parameter bits, see page 5-10.
Perform Auto-tuning (AT)
To perform auto-tuning (AT), turn on the control enable/disable bit (Bit0) and auto-tuning (AT)/auto-reset
bit (Bit1) of the operation parameter. P, I, D and ARW values will automatically be configured.
When auto-tuning (AT) is performed during the program control, P, I, D and ARW values of the current
step are configured. While auto-tuning (AT) is performed, the Auto-tuning (AT)/Auto-reset LED (AT0/AT1)
flashes.
When auto-tuning (AT) is completed, the operation parameter Bit1 is automatically turned off, and the
CPU module reads all parameters of the AT performed channel from the PID module and store those
parameters in the data registers. If any parameters in the data registers of the CPU module have been
changed but have not been written to the PID module, those parameters will be overwritten with the
parameters read from the PID module when auto-turning (AT) is finished.