AUX E&H Series Instrukcje Operacyjne Pobierz pdf (Strona 41)

5.6.2 P(ID) controller

The Liquisys M supports the definition of various controller functions. On the basis of the PID

controller, P, PI, PD and PID controllers can be implemented. The best control response is

obtained using the controller best suited to the application in question.Depending on the

selection in field R 237 / R 266, the set value can be output via relay or current output 2.

• P controller: Used for simple linear control purposes with small system deviations. Where

major changes are to be controlled, overshooting may occur. A control offset is to be

expected.

• PI controller: Used for processes where overshooting is to be avoided and permanent

offsets are not allowed.

• PD controller: Used for processes that require quick response and where peaks are to be

corrected.

• PID controller: Used for processes for which the type of control provided by a P, PI or PD

controller is inadequate.

Setting options of PID controller

There are three setting options for a PID controller:

• Control gain Kp (P impact)

• Integral action time T

(I impact)

• Derivative action time T

(D impact)

Start-up

If there are no empirical values available for setting the control parameters, use values that

provide the greatest possible stability of the control loop. To optimise the control loop further:

• Increase the control gain K

until the control variable just starts to overswing.

• Decrease K

again slightly and shorten the integral action time T

to achieve the shortest

possible correction time without overswing.

• In order to shorten the response time of the controller, you also have to set the derivative

action time T

PM253E5B.CHP

Liquisys M CPM 223 / 253 Instrument configuration

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AUX E&H Series Instrukcje Operacyjne Strona 41