Moniteur 50 Series SMART Positioners - Manual (Page 19)

Design and Method of Operation
2-1
Positioner SIPART PS2/SIPART PS2 PA
C79000-G7476-C150–01
Design and Method of Operation
This Section describes the mechanical and electrical design, the com-
ponents of the instrument and the principal method of operation of the
instrument.
2.1 Overview
The SIPART PS2 electropneumatic positioner forms a closed-loop con-
trol system together with an actuator. The current position of the actua-
tor is acquired via a servo-potentiometer and returned as actual value
x. The setpoint and actual values are output simultaneously on the dis-
play.
Setpoint w is formed by a current fed to the SIPART PS2 positioner
which is also used to power the instrument in 2-wire operations. In
3/4–wire operation the power supply is taken from a 24V power input.
The setpoint is supplied to the positioner by the control system digitally
via PROFIBUS PA.
The PROFIBUS PA variant of the SIPART PS differs from previous ver-
sions by its bus interface. The basic functions including operation and
display have remained almost unchanged. The interface tasks are per-
formed by function blocks 1 to 6 (see Fig. 2-13).
The positioner functions as a predictive 5-step controller, the output
quantity
±∆
y of which is used to operate the integrated control valves
with pulse-width-modulated pulses.
These positioning signals effect differences in pressure in the actuator
chamber(s) and consequently adjustment of the actuators until the sys-
tem deviation is reduced to zero.
Process operation (automatic and manual mode) and configuring
(structuring, initialization and parameterization) is performed with the
three pushbuttons and the display when the housing cover is removed.
The standard version of the basic instrument also has a binary input
(BE1). This input can also be configured individually and is primarily
intended for blocking operating levels.
Introduction
Devices without
PROFIBUS PA
Devices with
PROFIBUS PA
2