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Basic Examples of PID Control Section 5-1
5-1-4 PID Control for Switching PID Constants by Three Set Point Zones
Function blocks used: Basic PID (Block Model 011)
ITEM Setting (Block Model 171)
High/Low Alarm (Block Model 111)
Step Ladder Program (Block Model 301)
Register three sets of PID constants for switching in advance to the three
Constant ITEM Setting blocks. Input the current Set Point value of the Basic
PID block to the High/Low Alarm block. Three Set Point zones can be pre-
pared in the Step Ladder Program block by combining the high alarms and
low alarms of the High/Low Alarm block. Select the Constant ITEM Setting
block according to the Set Point zone.
MV
PV
Basic PID
Block Model 011
Analog input
Analog output
Contact Selector
Block Model 165
DI Terminal from
CPU Unit
Block Model 451
LSP
Contact switching
Contact
Distributor
Block Model 201
AI 4-point
Terminal
Block Model 586
AO 4-point
Terminal
Block Model 587
PID
MV
PV
PID1
PID1
PID1
Switching according to Set
Point zone
SP
PID3PID1
Low limit alarm
High limit alarm
PID2
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