Samson 3374-11 - Page 46

46 EB 8331-4 EN
Operating level
PID controller application
The set point adjustable at the actuator is used to position the valve using a PID algorithm.
The input signal is used as the process variable. The PID controller is adjusted using the pa-
rameters: Proportional-action coefcient Kp, Reset time Tn, Derivative-action time Tv and Op-
erating point Y
0
:
The proportional-action coefcient Kp acts as gain.
The reset time Tn is the time it takes for the integral component during a step response in a PI
controller to produce a change in the manipulated variable identical to the change produced
by the P component. Increasing the reset time Tn reduces the rate of change in the output
when the set point deviation is constant.
The derivative-action time Tv is the time it takes the rise response of a PD controller to reach a
certain manipulated variable value earlier than it would take the response with the P compo-
nent only. Increasing the derivative-action time Tv causes an increase in the manipulated
variable amplitude when the rate of change is constant. After ramped changes of the set
point deviation, a longer derivative-action time Tv causes the D component to have a longer
effect.
The operating point Y
0
determines the positioning value, which is fed to the controlled system
when the process variable is the same as the set point. The operating point is normally only
important for P and PD controllers, but it can also be set for control strategies PI, PID and I
due to the possible limitation of the integral-action component. For control strategies with in-
tegral-action component, the operating point can also be used as the initial value for a re-
start.
Î Set Code 6 to PID.
Î Use terminal assignment according to Fig.17.
Two-step mode application
The binary input IN2 is used for this function. When the binary input is in the active switch-
ing state, the actuator stem retracts to 100% of the adjusted travel range. When the binary
input is in the inactive switching state, the actuator stem moves to the closed position (0%).
Î Set Code 6 to 2STP.
Î Use terminal assignment according to Fig.18.
Three-step mode application
The binary input IN2 is used for this function to retract the actuator stem and binary input
IN3 to extend the actuator stem.
Î Set Code 6 to 3STP.
Î Use terminal assignment according to Fig.19.