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XTC/3 Operating Manual
CONTROL GAIN
. . . . . . 0.01 to 100.0 Å/sec/% Pwr
This parameter determines the change in % Power for a given rate deviation
(dRate/dPower). The larger the process gain value, the smaller the change in
power for a given rate error. The default is 10 Å/s/% Pwr.
Figure 4-6 Control Gain
TIME CONSTANT
. . . . . 0.1 to 100.0 sec
This is the evaporation source’s time constant. This value is defined as the time
difference between the actual start of a change in rate and the time at which 63%
of the rate step is achieved. This value may be measured according to the above
criterion or it may be determined empirically. The default value is 1.
Figure 4-7 Time Constant
R
A
T
E
P
O
W
E
R
Å/s
%
delta Rate = 10
20
19
20
10
0
delta Power = 1
CONTROL GAIN = dRate / dPower = 10/1 = 10
TIME
R
A
T
E
P
O
W
E
R
TIME CONSTANT
TIME
RATE INCREASE
Power
Rate
63% POINT
0