6.5.2.1 Example of Process PID Control
The following is an example of process PID control used in
a ventilation system:
Figure 6.19
In a ventilation system, the temperature is to be settable
from 23°–95° F [-5°–35
°
C] with a potentiometer of 0–10 V.
The set temperature must be kept constant, for which
purpose the Process Control is to be used.
The control is of the inverse type, which means that when
the temperature increases, the ventilation speed is
increased as well, so as to generate more air. When the
temperature drops, the speed is reduced. The transmitter
used is a temperature sensor with a working range of 14°–
104° F [-10°–+40
°
C], 4-20 mA. Min./Max. speed 300/1,500
RPM.
Figure 6.20 Two-wire Transmitter
1.
Start/Stop via switch connected to terminal 18.
2.
Temperature reference via potentiometer (23°–95°
F [-5°–35
°
C], 0–10 V DC) connected to terminal
53.
3.
Temperature feedback via transmitter (14°–104° F
[-10°–+40°
°
C], 4–20 mA) connected to terminal
54. Switch S202 set to ON (current input).
6.5.2.2 Ziegler Nichols Tuning Method
NOTE!
The method described must not be used on applications
that could be damaged by the oscillations created by
marginally stable control settings.
The criteria for adjusting the parameters are based on
evaluating the system at the limit of stability rather than
on taking a step response. We increase the proportional
gain until we observe continuous oscillations (as measured
on the feedback), that is, until the system becomes
marginally stable. The corresponding gain
(K
u
)
is called the
ultimate gain. The period of the oscillation
(P
u
)
(called the
ultimate period) is determined as shown in the figure.
Application Setup Examples
AF-650 GP
TM
Design and Installation Guide
6-18
DET-767A
6
6
Summary of Contents for AF-650 GP Series
Page 3: ...Safety AF 650 GPTM Design and Installation Guide DET 767A ...
Page 9: ...Contents AF 650 GPTM Design and Installation Guide DET 767A ...
Page 19: ...Introduction AF 650 GPTM Design and Installation Guide 1 10 DET 767A 1 1 ...
Page 35: ...Installation AF 650 GPTM Design and Installation Guide 2 16 DET 767A 2 2 ...
Page 41: ...Start Up and Functional Tes AF 650 GPTM Design and Installation Guide 3 6 DET 767A 3 3 ...
Page 55: ...About Programming AF 650 GPTM Design and Installation Guide 5 10 DET 767A 5 5 ...
Page 91: ...Application Setup Examples AF 650 GPTM Design and Installation Guide 6 36 DET 767A 6 6 ...
Page 103: ...Status Messages AF 650 GPTM Design and Installation Guide 8 4 DET 767A 8 8 ...
Page 123: ...Warnings and Alarms AF 650 GPTM Design and Installation Guide 10 10 DET 767A 10 0 ...
Page 127: ...Basic Troubleshooting AF 650 GPTM Design and Installation Guide 11 4 DET 767A 11 1 ...
Page 129: ...Terminal and Applicable Wir AF 650 GPTM Design and Installation Guide 12 2 DET 767A 12 2 ...
Page 161: ...Specifications AF 650 GPTM Design and Installation Guide 13 32 DET 767A 13 3 ...