Type 8696 Positioner; Schematic Representation Of The Position Control Type 8696 - bürkert TopControl Basic 8696 Bedienungsanleitung

Type 8696
Systemdescription
5.6 Type 8696 positioner
The position measuring system records the current position (POS) of the pneumatic actuator. The positioner com-
pares this actual position value with the set-point value (CMD), which is definable as norm signal. In case of a control
deviation (Xd1), a pulse-width modulated voltage signal is sent to the control system as a manipulated variable. If
there is a positive control difference in single-acting actuators, the air inlet valve is controlled via output B1. If the
control difference is negative, the bleed valve is controlled via output E1. In this way the position of the actuator is
changed until control difference is 0. Z1 represents a disturbance variable.
CMD
Position
set-point
value
Figure 5: Signal flow plan of positioner
5.6.1 schematic representation of the position control Type 8696
4 ... 20 mA
2)
0 ... 20 mA
INP
DIR.CMD
SPLTRNG
Default setting
2)
can only be activated with communications software
3)
Figure 6: Schematic representation of the position control
Xd1
+
-
Position
controller
Position control circuit
DIR.ACT
CHARACT
CUTOFF
3)
Z1
B1
P
K
E1
Control system Control valve
Solenoid valves
POS
Position measuring system
POS
X.LIMIT
3) 3)
X.CONTROL
CMD DBND
X.TIME
3)
Valve opening
POS
CMD
english
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