Ohkura EC5500R, Instruction Manual, Page: 43 / 56

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8.5 Self Tuning
Unlike automatic tuning which is executed only when the operator intends,
Self tuning is the function to execute automatic tuning when the stability
of control exceeds the limit or setting changes in steps, etc. by monitoring
the existence of deviation, hunting, etc. continuously from the controller.
Since the output is not changed in steps as in automatic tuning, there is
no disturbance by tuning.
The conditions to update the PID to optimal value during Self tuning
(when display is
and TUNE lamp is ON) are as follows:
a: When SP is changed by 0.5% FS (full scale) or larger in steps with
stable PV,
b: When PV or output fluctuation is detected for 3 cycles for more (it
may take more time depending on the furnace features and the PID
value at fluctuation),
c: When PV is stable and SP is larger than PV by 2% FS or larger at
turning on this instrument.
[Caution]
Though PID can be changed manually from surface key or external
communication during Self tuning, the set PID may be overwritten by
the tuning result depending on the control status.
[Caution]
Self tuning can be executed for single output type with PID control,
reverse action, no square root and except the master controller of
profiling control. In addition, TUNE lamp goes OFF during MAN and
control STOP even when Self tuning is ON, and Self tuning is not
operated during this period.
[Reference]
PV stability is judged by the following conditions:
At turning on the power: Stability within
±
0.08% FS continues for 2
seconds or longer.
At normal control: Stability within
±
0.08% FS continues for 1/2 of the
current integration time.
[Caution] Precautions for use
Self tuning execution is maintained when turning off the power during
Self tuning. An inappropriate PID may be calculated if the furnace is
turned on the power after changing SP with furnace power OFF during
Self tuning. Change SP with the furnace power ON. Turns off the
instrument once and then turns on again if the difference between SP
and PV stays large even after specified period (it varies by the furnace
features).