MKS MKSINST IE1000A, Инструкция по эксплуатации

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General Operational Functions Chapter Three: Operation
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Derivative Term
The action of the Derivative (D) term creates a valve drive signal that is proportional to the rate of change of
the error signal over time. In moderate amounts, it can be used to reduce overshoot within the system by
adding predictive capabilities to the control algorithm. At high rates of change of the error signal as it
approaches the setpoint quickly (negative slope of the absolute error over time), the derivative term reduces
the effects of the Proportional term. Excessively high Derivative term values can result in instability of the
controller. In general, IE500A / IE1000A Mass Flow Controllers control well with the Derivative term equal
to zero.
Optimizing PID Control Settings
Optimizing the IE1000A High Flow Rate Mass Flow Controller response in your system involves adjusting
the Proportional, Integral, and Derivative (PID) terms. Since every system is different, the optimum PID
settings may vary. Operating pressures, process gas density, and target setpoints, all contribute to determining
the ideal settings.
Guidelines for Optional Input Control Tuning
Tuning is best done with setpoint changes from zero to the target flow rate.
Increasing the I term will reduce response time, especially at setpoints below 20% of full scale, but
promote flow overshoot during setpoint changes. Increasing the P term reduces the overshoot because the
controller is able to respond more quickly to the indicated overshoot. However, an excessive P term will
cause controller oscillation, a highly undesirable condition. Thus, caution must be exercised in setting the
P term aggressively.
Any adjustments to the P and I terms (D is generally kept at zero) should be done incrementally. If
excessive overshoot is observed, the P value may be increased somewhat. For improved control stability,
the I term should be
decreased in small increments.