LG Electronics 120S user manual System response when a long integration time given

Chapter 7 Usage of Various Functions

Fig. 2.5 The system response when a long integration time given

Fig. 7.4 The system response when a long integration time given

Fig. 2.6 The system response when a short integration time given

Fig. 7.5 The system response when a short integration time given

(c)Derivative operation (D action)

①When a deviation occurs due to alteration of SV or external disturbances, D action restrains the changes of the deviation by producing MV which is proportioned with the change velocity (a velocity whose deviation changes at

every constant interval) in order to eliminate the deviation.

②D action gives quick response to control action and has an effect to reduce swiftly the deviation by applying a large

control action (in the direction that the deviation will be eliminated) at the earlier time that the deviation occurs.

③D action can prevent the large changes of control object due to external conditions.

④The period of time from when the deviation has occurred to when the MV of D action become the MV of P action is called derivative time and represented as Td.

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