...5 CONTROL OPERATION
...5.9 Introduction to Standard Control
Decrease Proportional Band
Response Time
Time
28
Initial Settings
•
Proportional Band = 100%
•
Integral Action Time = OFF
•
Derivative Action Time = OFF
•
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 value
Observe response of process
Response Time
•
Note Proportional Band value (PBc)
•
Measure the critical cycle time (tc)
Calculate Terms
P
P
P+I
2 x PBc
2.2 x PBc
I
—
tc/1.2
D
—
—
Fig. 5.17 Manual Tuning
Critical
Cycle time (tcc)
P+D
P+I+D
1.6 x PBc
1.6 x PBc
tc/2
tc/2
tc/12
tc/8
Increase Proportional Band
Response Time
Time