User Manual Owner's manual

EAF
Process Control Instructions
Chapter 16
16-4
Independent Gains
Using the independent gain equation you adjust the proportional, integral
and derivative terms separately.
CO + K
P
E ) K
I
ŕ
Edt )
KD[E * E(n * 1)]
dt
) Bias
t
o
CO + K
P
E ) K
I
ŕ
Edt )
KD[PV * PV(n * 1]
dt
) Bias
t
o
or
where: C= control output
K
P
= proportional gain constant (unitless)
K
I
= integral gain constant (1/sec)
K
D
= derivative gain constant (sec)
dt = time between samples
Bias = feedforward or output bias
E = error equal to (PV – SP) or (SP – PV)
E(n-1) = error from last sample
PV = process variable
PV(n-1) = process variable from last sample
You can convert dependent gain constants to independent gain constants by
using the following formulas:
K
P
= K
C
K
I
= K
C
/(Ti(60 sec/min))
K
D
= K
C
(TD)(60 sec/min)
For more information about PID control, see the Fundamentals
of Process
Control Theory by Paul W. Murrill (Instrument Society of America).