28
Increase Proportional Band
P
I
D
Initial Settings
Observe response of process
Adjust the set point a small amount
Hold the set point at the new value until
the process begins to move
Reset the set point to the original valuee
Proportional Band = 100%
Integral Action Time = OFF
Derivative Action Time = OFF
Note Proportional Band value (PBc)
Measure the critical cycle time (tc)
P
2 x PBc
—
—
P+I
2.2 x PBc
tc/1.2
—
P+D
1.6 x PBc
tc/2
tc/12
Time
Process Variable
Response Time
•
•
•
•
•
•
•
•
Time
Process Variable
Response Time
Process Variable
Response Time
Critical
Cycle time (tcc
Decrease Proportional Band
Calculate Terms
P+I+D
1.6 x PBc
tc/2
tc/8
…5.9 Introduction to Standard Control
Fig. 5.17 Manual Tuning
…5 CONTROL OPERATION
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