Design And Method Of Operation; Overview - Siemens SIPART PS2 6DR5020 Series Manual

Design and Method of Operation

2.1

Overview

Introduction
SIPART PS2 Manual
A5E00074631-01
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 actuator is detected by a
servo potentiometer and fed back as actual value x. The setpoint and
actual value are output simultaneously on the display.
The setpoint w is formed by a current fed to the positioner which at the
same time serves to supply the positioner in two-wire operation. In 3 /
4-wire operation the supply comes from a 24 V voltage input.
The positioner operates as a predicative five--point switch by the output
variable ±Dy 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 pa-
rameterization) is effected by three keys and a display with the housing
cover removed.
The standard controller has one digital input (DI1). This can be configu-
red individually and can be used for blocking the operating levels for
example.
With the J -option module, the current actuator position can be output
y
as a two wire signal J
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.
The limit value alarms are output by the alarm option module which can
monitor and report the function of the positioner and the actuator addi-
tionally through a fault message output. The value of the control diffe-
rence dependent on the floating time is monitored in automatic mode.
The fault signal is always set when the control error cannot be leveled
after a certain time because for example the valve is blocked or the
mains pressure is insufficient. The three digital outputs are implemen-
ted as semiconductor outputs and are error self--reporting, i.e. the out-
Design and Functional Principle
= 4 to 20 mA.
y
2
15