User Manual

Load Initial Configuration Values
Chapter 7
7-30
Comparison of Gain Constants
Compare dependent and independent gains constants as follows:
Dependent Gains Constants: Independent Gains Constants:
Controller Gain K
c
(dimensionless) Proportional Gain K
p
(dimensionless)
Reset Term 1/T
i
(minutes per repeat) Integral Gain K
i
(inverse seconds)
Rate Term T
d
(minutes) Derivative Term K
d
(seconds)
Other variables used in any algorithm choice include:
Output = Percentage of full scale
E = Error (scaled) SP-PV (Setpoint-Process Variable)
PV = Process Variable (scaled)
Convert from dependent to independent gains constants by substituting
controller gain (K
c
), reset (1/T
i
), and rate (T
d
) values in these formulas:
K
p
= K
c
unitless
K
i
=
K
c
60 T
i
inverse seconds
K
d
= K
c
(T
d
)60 seconds
We entered bit B07 = 1 for A-B independent gains on all corresponding
worksheets.
Important: PID gain constants that we entered on worksheets and used in
closed-loop tuning procedures in chapter 10 were independent (A-B) gains.
If, after attempting to tune your pressure loops in chapter 10, you believe
you must use dependent (ISA) gain constants, refer to Section 3 of the
Plastic Molding Module Reference Manual (publication 1771-6.5.88) for
information on this option.