7-10
Chapter 7. PARAMETER SETUP
●
otL (MV change limit) (CH1)
The MV is increased or decreased by the same value so that the output change is
taken as the limit setting value when the output change (%) after PID operation is
greater than this limit setting.
The following example shows the actual change in MV when the MV changes
from 20% to 22% with the change limit setting at 0.5%. MV is output at 0.5%
setting value increments every 0.1 seconds, and reaches 22% in 0.4 seconds.
●
IoUt (PID operation initial MV) (CH1)
PID operation is started in the following cases using the
IoUt
setting value:
• When the mode changes from READY AUTO to RUN AUTO
• When the power is turned ON in the RUN AUTO (or HOLD, FAST, END
AUTO) mode
• At completion of auto-tuning
As the PV, SP and PID parameters settings bear a relation to PID operation, the
first MV resulting from PID operation will not necessarily match the
IoUt
setting
value.
●
rPId (PID operation initialization) (CH1)
When SP changes suddenly by ADV (advance) operation, rate action in PID
operation may cause the MV in the operation to change excessively. For this
reason, excessive changes can be suppressed by initializing PID operation.
However, as initialization may result in lost continuity of PID operation,
initialization may adversely influence PID operation depending on the
circumstances in which the DCP32 is being used.
Initialization ON/OFF and conditions can be selected by the
rPId
setting.
●
St (smart-tuning method selection) (CH1)
0: Smart-tuning is disabled.
1: The brake value is fixed to inhibit overshoot.
2: Overshoot is inhibited while automatically reviewing the brake value.
• When the control direction is set to reverse action, overshoot is inhibited. When
set to direct action, undershoot is inhibited. Both functions are referred to
collectively as “overshoot inhibit”.
When set to 1, the value of PID parameter setting item
br
(brake) is used as it is
to inhibit overshoot.
When set to 2, the value of
br
is reviewed at each rise (reverse action) or fall
(direct action), and overshoot is inhibited while the value is automatically
rewritten.
Review is executed only in the direction in which the
br
value is increased
(overshoot inhibit effect becomes more apparent).
When operation is carried out for a long time with this parameter set to 2,
overshoot inhibit may function too strongly, and it may take a long time to
arrive at SP. So, when overshoot disappears, note down the
br
value at that time,
set
St
to 1, and reset the
br
value to the noted down value.
%
t
t+0.1
t+0.2
t+0.3
t+0.4
20
21
22
s
