5-7
Chapter 5. DETAILED DESCRIPTION OF EACH FUNCTION
PV filter
This PV filter is a primary delay filter to be used if the PV repeatedly fluctuates
rapidly and the control cannot be performed or if the PV fluctuates finely due to
influence of noise, etc.
As a larger value is set, it becomes difficult to change the PV used for the control of
this unit.
Normally, the PV filter is used with an initial value of "0.0".
Item (Bank) Display Contents Initial value User level
PV filter
(Parameter bank)
0.0: No filter
0.1 to 120.0 s
0.0 s Basic,
Standard,
High function
OUT = OUT
-1
+ (IN − OUT
-1
)/(T/T
s
+ 1)
IN: Input to filter
OUT: Control output of current filter
OUT
-1
: Control output of previous filter
T: Filter set value (s)
T
s
: Sampling cycle time (0.5 s)
PV hold
It is possible to set the PV to a fixed value using the PV hold, PV Max. hold, and PV
Min. hold of the digital input (DI) functions.
PV hold: PV is set to a fixed value and it is not updated.
PV Max. hold: PV maximum value is held.
The PV value is updated only when the new PV value is larger
than the currently held value.
PV Min. hold: PV minimum value is held.
The PV value is updated only when the new PV value is smaller
than the currently held value.
When using the PV hold, PV Max. hold, or PV Min. hold, the PV indication on the
upper display is flashing.
PV low limit/high limit and PV low limit/high limit alarms
PV low limit and PV high limit are provided for each PV input range type.
In principle, -10%FS of each range becomes the PV low limit while +110%FS
becomes the PV high limit.
For details,
Behavior in case of PV input failure (p.10-3).
The PV is limited so that it is within a range between the PV low limit and PV high
limit.
If the PV before activation of the PV ratio, PV bias, and PV filter is larger than the
PV high limit, PV high limit alarm (
AL0
1
) occurs. On the contrary, if this PV is
smaller than the PV low limit, the PV low limit alarm (
AL02
) occurs.
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