MKS 651D Series, User Manual, Page: 39 / 162

Chapter Three: Overview Control Mode
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Gain
Gain provides a control signal that is directly proportional to the error signal. The error signal is
the difference between the actual pressure and the set point. This gain is responsible for
controlling how quickly the pressure responds to a change in set point. A large gain generally
results in a faster response to set point. However, if the gain is too small, the system will be
slow in responding to set point (refer to Figure 7). If the gain is too high, the pressure will
overshoot and then oscillate around the set point before settling in (refer to Figure 6).
Pressure
Time
Set Point
Figure 6:Gain Set Too High
Pressure
Set Point
Time
Figure 7: Gain Set Too Low