Basic Examples of PID Control
Section
5-1
155
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
prepared 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.
PID
MV
PV
PID1
PID1
PID1
Switching according to Set
Point zone
SP
PID3
PID1
Low limit alarm
High limit alarm
PID2
Basic PID
Block Model 011
MV
PV
Constant ITEM
Setting
Block Number
171
Analog input
P,I,D
AI 4-point Terminal
Block Number 586
Analog output
Constant ITEM
Setting
Block Number
171
Constant ITEM
Setting
Block Number
171
Step Ladder
Program
Block Model 301
High/Low Alarm
Block Model 111
High
limit
Low
limit
SP
AO 4-point
Terminal Block
Number 587