Siemens SIPART PS2 6DR50xx Instrucciones de operaciones descargar pdf (Pagina 29)

Description

3.5 Mode of operation

SIPART PS2 with and without HART communications

Operating Instructions, 09/2007, A5E00074631-07

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Figure 3-14 Restrictors

① Restrictor Y1

② Restrictor Y2, only in the version for double-acting actuators

③ Hexagon socket-head screw 2.5 mm

See also

Pneumatic connection in the flameproof enclosure (Page 26)

Sequence of automatic initialization (Page 108)

3.5 Mode of operation

3.5.1 Control loop

Control loop

The electropneumatic positioner forms a control loop with the pneumatic drive:

● The actual value x represents the position of the drive spindle for linear actuators or the

position of the drive shaft for part-turn actuators.

● The control value w represents the positioning current of a closed-loop controller or a

manual control station from 0/4 to 20 mA.

The lifting or rotary movement of the actuator is transferred to a high-quality conductive

plastic potentiometer using suitable attachments, feedback shaft and a backlash-free,

switchable gear drive, and then to the analog input of the microcontroller. The current

position can also be forwarded to the positioner using an external sensor. A Non-Contacting

Position Sensor is used to record the lifting or rotation angle directly on the actuator.

If required, the microcontroller corrects the angle error of the feedback lever bracket,

compares the potentiometer voltage as an actual value x with the setpoint w that is fed

through terminals 3 and 7, and calculates the controller output increment ±∆y. Depending on

the magnitude and the direction of the control deviation (x-w), the piezo advance controlled

supply or exhaust air valve is opened. The actuator volume integrates the controller

increment for the actuating pressure y which is proportional to the drive rod or the drive

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Siemens SIPART PS2 6DR50xx Instrucciones de operaciones Pagina 29