RESET (INTEGRAL) CONTROL SYSTEMSProcess ControlsFigure 20 Integral Flow Rate ControllerInitially, the system is set up on an anticipated flow demand of 50 gpm, which corresponds toa control valve opening of 50%. With the setpoint equal to 50 gpm and the actual flow measuredat 50 gpm, a zero error signal is sent to the input of the integral controller. The controller outputis initially set for a 50%, or 9 psi, output to position the 6-in control valve to a position of 3 inopen. The output rate of change of this integral controller is given by:Output rate of change = Integral constant x % ErrorIf the measured variable decreases from its initial value of 50 gpm to a new value of 45 gpm,as seen in Figure 21, a positive error of 5% is produced and applied to the input of the integralcontroller. The controller has a constant of 0.1 seconds^{-1}, so the controller output rate of changeis 0.5% per second.IC-07 Page 30 Rev. 0

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