D8 Series User’s Guide
Chapter 5: Tuning and Control
91
Integral Settings
The controller’s integral parameter is set in seconds per repeat. Some other products use an
integral term called reset, in units of repeats per minute. Table 5.2 shows integral settings versus
reset settings.
Table 5.2
– Integral Term and Reset Settings
INTEGRAL
(SECONDS/REPEAT)
RESET
(REPEATS/MINUTE)
INTEGRAL
(SECONDS/REPEAT)
RESET
(REPEATS/MINUTE)
30
2.0
210
0.28
45
1.3
240
0.25
60
1.0
270
0.22
90
0.66
300
0.20
120
0.50
400
0.15
150
0.40
500
0.12
180
0.33
600
0.10
As a general rule, use 60, 120, 180 or 240 as a starting value for the integral.
Derivative Settings
The controller’s derivative parameter is programmed in seconds. Some other products use
a derivative term called rate programmed in minutes. Use the table or the formula to convert
parameters from one form to the other. Table 5.3 shows derivative versus rate. Rate = Derivative/60.
Table 5.3
– Derivative Term Versus Rate
DERIVATIVE
(SECONDS)
RATE
(MINUTES)
DERIVATIVE
(SECONDS)
RATE
(MINUTES)
5
0.08
35
0.58
10
0.16
40
0.66
15
0.25
45
0.75
20
0.33
50
0.83
25
0.41
55
0.91
30
0.50
60
1.00
As a general rule, set the derivative to 15 percent of integral as a starting value.
NOTE!
While the basic PID algorithm is well defined and widely recognized, various
controllers implement it differently. Parameters may not be taken from one controller
and applied to another with optimum results even if the above unit conversions are
performed.
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