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Design and method of operation
2.1
Overview
Introduction
SIPART PS2 PA Manual
A5E00127926--05
The following chapter describes the mechanical and electrical design,
the instrument components and method of operation of the positioner.
The electropneumatic positioner forms a control system in connection
with an actuator. The current position of the positioner is detected by a
servo potentiometer and fed back as actual value x. In addition a
separate sensor can be fitted to the positioner for purposes of position
detection. The setpoint and actual value are output simultaneously on
the display.
The setpoint is set by the control system and passed to the positioner
by the PROFIBUS PA digitally.
The PROFIBUS PA variant of the positioner differs from previous
versions in the bus interface. The basic functions of the positioner
including operation and display are virtually unchanged.
The positioner operates as a predictive five--point switch by the output
variable ±∆y of which the integrated actuating valves are controlled with
pulse length modulation.
These actuating signals cause fluctuations in pressure in the actuator
chamber(s) and thus adjustment of the actuator until the control error is
zero.
Operation (manual) and configuration (structuring, initialization and
parameterization) is effected by three keys and a display with the
housing cover removed.
The standard controller has one binary input (BI1). This can be
configured individually and can be used for blocking the operating
modes for example. A further input (Shut down) has the function of
moving the actuator to a pre--set safety position (end stop).
With the I
-option module, the current actuator position can be output
y
as a two wire signal I
y
In addition the actuator can be monitored for two programmable limit
values which respond on exceeding or dropping below the stroke or
angle of rotation.
Design and method of operation
= 4 to 20 mA.
2
23
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