INFICON XTC/C Thin Film Deposition Controller - Manual (Page 117)

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XTC/C - XTC/2 Operating Manual
As illustrated in Figure 5-7 on page 5-13 , the control dead time, L, is the time
delay between a change in the source’s power setting and a noticeable change
in deposition rate. The control time constant, T
1
is (T
0.632
- L) where T
0.632
is
the time between a change in the source’s power setting and the time to
achieve 63.2% of the new equilibrium rate.
K
P
is then the ratio of the change in rate over the change in source power
setting.
[1]
These values may be adjusted slightly in use to optimize the tuning. The tuning
may change because of process variations. Usually CTL TC and CTL DT do
not need to be changed.
NOTE: Remember that increasing the value of CTL GAIN reduces the
controller change for a given rate error.
Figure 4-7 Examples of Delay Settings
K
p
(change in output)
(change in control signal)
-------------------------------------------------------------------
Å sec
⁄ ∆
%Pwr
∆
--------------------- = =