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Description
3.1
Function
● The electropneumatic positioner, in combination with the actuator, forms a control
system. The current position of the actuator is detected using a potentiometer and
returned as the actual value x. The setpoint and actual value are output simultaneously
on the display.
● The setpoint w forms a current applied to the positioner, which in two-wire mode is also
used to power the positioner. In 3- and 4-wire mode, power is supplied through a 24-V
power input.
● The positioner works as a predictive five-point controller, through whose output value ±Δy
the integrated valves can be controlled by pulse length modulation.
● These positioning signals cause pressure changes in the actuator chamber(s) and thus
repositioning of the actuator until the control deviation returns to zero.
● Using three buttons and the display with the enclosure cover removed, operation (manual
mode) and configuration (structuring, initialization, and parameter assignment) can be
performed.
● By default, the basic electronics has a binary input (BIN1). This binary input can be
individually configured and used e.g. to block the control levels.
● To be able to use the positioner in a variety of mechanically different rotational and linear
actuators, it has a friction clutch and a switchable gear.
● In the case of positioners with the "Fail in Place" function, the current position of the
actuator is held if the electric and/or pneumatic auxiliary power fails. Does not function in
conjunction with SIL.
3.2
Structure
3.2.1
Overview of structure
The following sections describe the mechanical and electrical structure, components, and
principle functionality of the positioner.
The positioner is used to move and control pneumatic actuators. The positioner works
electropneumatically, using compressed air as auxiliary power. The positioner is used to
control valves, for example, with:
● Linear actuator
● Part-turn actuator VDI/VDE 3845
SIPART PS2 with and without HART
Operating Instructions, 09/2014, A5E00074631-12
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