Azbil KFDB, Руководство пользователя

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10
(3) Other Controller Units
a) ON/OFF Unit
This unit is used for control of process whose time constant is large but dead time
is small. This unit is structured by eliminating the feedback mechanism from the
proportional control unit so that the nozzle back pressure is directly applied to the
pilot relay. The ON/OFF actions take place depending on whether the nozzle is
uncovered or covered by the flapper.
b) Differential Gap Unit
This unit is used in such case that, if the ON/OFF controller is used, ON/OFF action
will be repeated too frequently and the actuator or other device will be ad versely
affected.
This unit is structured by replacing the feedback chamber of the proportional unit
with a spring and feeding the output pressure of the pilot relay to the integral chamber.
The differential gap width is adjustable for a range of 1 to 100 %.
c) Manual Reset Unit
This unit is structured so that the output pressure of the pilot relay is applied to the
feedback chamber of the proportional unit and a reset pressure (20 to 100 kPa {0.2 to
1.0 kgf/cm
2
}) manually generated with a pressure regulator is applied to the integral
(reset) chamber.
d) External Reset Unit
This unit differs from the manual reset unit in that an external reset signal (20 to 100
kPa {0.2 to 1.0 kgf/cm
2
}) is employed instead of generating it manually (locally) with a
pressure regulator. The external pressure signal should be connected to the RES port
of the controller.
Fig. 1-8. Differential Gap