ABB C1900 Series Operating Manual page 30

...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