Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 236)

Comparing ISA/1771-PD Algorithms
Appendix E
EĆ2
Word ISA Algorithm AĆB Algorithm
W07 (W14) Proportional Gain K
C
(dimensionless)
Proportional Gain K
P
(dimensionless)
W24(W44) Reset Term 1/T
I
repeats per minute)
Integral Gain K
I
(inverse seconds)
W25(W45) Rate Term T
D
(minutes)
Derivative Gain K
D
(seconds)
Conversion
Converts ISA standard values to 1771-PD values as follows:
K
P
=K
C
K
I
= K
P
(# repeats per minute
60
K
D
=K
P
(T
D
)(60)
Example
If you desired ISA standard values are:
controller gain = K
C
= 1
reset value = 1/T
I
= 5 repeats per minute
rate term = T
D
= 3 minutes
convert them to 1771-PD values as follows:
proportional gain = K
P
= K
C
= 1
integral gain = K
I
= (1)(5) = 0.083
60
derivative gain = K
D
= (1)(3)(60) = 180
Insert the converted gain values into the 1771-PD algorithm as follows: