Description
3
3.1 Function
● The electropneumatic positioner and an actuator form a control loop. The current position
of the actuator is recorded by a servo potentiometer and the actual value x is fed back. The
setpoint and the actual value are also shown simultaneously on the display.
● The positioner works as a predictive five-point positioner, through whose output value ±Δy
the pneumatic block can be controlled by pulse length modulation.
● These control signals cause pressure changes in the actuator chamber(s) and thus an
adjustment of the actuator until the control deviation becomes zero.
● The three keys and the display are used to operate (manual mode) and configure
(structuring, initializing and parameter assignment) with the enclosure cover removed.
● By default, the basic unit has a digital input. This digital input is individually configured and
blocks the operating levels, for example.
● The positioner has a friction clutch and a selectable gearbox. It can therefore be used on a
large number of mechanical part-turn and linear actuators.
● 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
Various add-on extensions are available for linear actuators:
● IEC 60534-6-1 (NAMUR)
● Integrated mounting on ARCA, except with flameproof stainless steel enclosure (6DR5..6)
● Integrated mounting on SAMSON, not for Ex d
SIPART PS2 with 4 to 20 mA/HART
Operating Instructions, 11/2019, A5E00074631-AE 23
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