Type 8694 Positioner (Position Controller); Schematic Representation Of The Position Control Type 8694 - Burkert 8694 Operating Instructions Manual

5.5. Type 8694 positioner (position controller)
The position measuring system records the current position (POS) of the pneumatic actuator. The position controller
compares this actual position value with the set-point value (CMD) which is definable as standard signal. In case
of a control deviation (Xd1), a pulse-width modulated voltage signal is sent to the control system as a manipu-
lated 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.
Position
set-point
value
Figure 4: Signal flow plan of position controller
5.5.1. schematic representation of the position control Type 8694
4 ... 20 mA
0 ... 20 mA
INP
DIR.CMD
Default setting
1)
Can only be activated with communications software
2)
Figure 5: Schematic representation of position control
16
CMD Xd1
+
-
Position
controller
Position control
circuit
1)
CHARACT
SPLTRNG
2)
English
B1
E1
Control system
Solenoid valves
POS
Position measuring system
POS
DIR.ACT
2) X.LIMIT 2)
CMD
CUTOFF X.TIME
2)
Type 8694
System description
Z1
P Valve opening
K
Control valve
X.CONTROL
DBND
POS
CMD