INFICON IC/5 Thin Film Deposition Controller - Manual (Page 49)

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IC/5 Operating Manual
Figure 2-7 Response of Process To An Open Loop Step Change
(At t=0 Control Signal is Increased)
A controller model used extensively is the PID type, shown in Laplace form in
equation [9] .
[9]
Where
 M(s) = manipulated variable or power
 K
c
= controller gain (the proportional term)
 T
i
= integral time
 T
d
= derivative time
 E(s) = process error
Figure 2-8 represents the controller algorithm and a process with first order lag plus
a dead time. The process block implicitly includes the dynamics of the measuring
devices and the final control elements, in our case the evaporator power supply.
R(s) represents the rate setpoint. The feedback mechanism is the error generated
by the difference between the measured deposition rate, C(s), and the rate set
point, R(s).
M s   K
c
1
1
T
i
s
------- T
d
s + +
 
  Es
=