Nor-Cal SDC15 Controller - Manual (Page 56)

■ 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".
OUT = OUT
-1
+ (IN – OUT
-1
)/(T/Ts + 1)
IN: Input to PV filter
OUT: Control output of current filter
OUT
-1
: Control output of previous filter
T: Filter set value (s)
Ts: Sampling cycle time (0.5s)
■ 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 DI (digital input) 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,
refer to page 10-2 .
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 (AL01) occurs. On the contrary, if this PV is
smaller than the PV low limit, the PV low limit alarm (AL02) occurs.
5-6
Chapter 5. DETAILED DESCRIPTION OF EACH FUNCTION
Item (Setting display/bank) Display Contents Initial value User level
PV filter
(Parameter
setting/Parameter bank) 0.0: No filter
0.1 to 120.0s 0.0s Simple,
Standard,
High function