C6-15
IM 34M06H62-02E 2nd Edition : June 2008-00
C6.9.2 Zone PID Selection
Setting the Zone PID Selection (ZONE) parameter to “1: Enabled” selects Zone PID
Selection as the PID selection method.
The Zone PID Selection method switches between PID parameter groups automatically
depending on the PV value. It can be used in chemical reaction apparatus where the
chemical reaction gain changes with temperature.
As shown in the figure below, the input range defined by the upper and lower limits can
be divided into three zones using the Reference Point 1 (1RP) and Reference Point 2
(2RP) parameters. You can assign optimal PID values for each of these zones. As the PV
value moves from the current zone to a different zone, the module automatically switches
to the PID values assigned to that new zone.
Input range lower limit
Reference point 1
Input range upper limit
Reference point 2
Changes in PV
If the current PV is here, control
proceeds using PID constants of
group 3.
PID 3
PID 2
PID 1
Figure C6.14 Zone PID Selection
Table C6.9 Parameters Related to Zone PID Selection
Data Position Number
Symbol Description Unit Data Range
Default
Value
Attribute
Stored
Loop1 Loop2 Loop3 Loop4
186 386 586 786 1RP Reference Point 1 Industrial unit PRL to PRH PRH RW
187 387 587 787 2RP Reference Point 2 Industrial unit PRL to PRH PRH RW
Note: If 1RP ≥ 2RP, the 2RP parameter is handled as though its value is equal to 1RP.
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