Azbil KFDB, Руководство пользователя

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Fig. 1-5. Deviation Generating Mechanism
1-6-3. Controller Mechanism
The controller mechanism is comprised of a proportional unit, an integral unit and/
or a derivative unit. The various combinations of these controller units are possible and
interchangeable to best suit the characteristics of the process to be controlled.
(1) Proportional (P) Unit
This unit is comprised of a nozzle-flapper mechanism and a feedback mechanism (a
feedback chamber and a reset chamber). Movement of the deviation link is conveyed
to the nozzle flapper mechanism via the flapper pin, which is linked with the feedback
link, to change the gap between the nozzle and flapper, thereby changing the nozzle back
pressure.
The nozzle back pressure is amplified by the pilot relay to the level of a regular pneumatic
control signal. The amplified pneumatic output pressure of the controller is fed back to
the nozzle flapper mechanism via the feedback chamber to change negatively the gap
between the nozzle and flapper. The controller mechanism reaches an equilibrium state
when the pneumatic output pressure proportional to the input deviation is attained.
Proportional band is adjustable by turning the proportional band dial. As this dial is
turned, the angles made up by the flapper, deviation link and feedback link are varied.