bürkert TopControl 8630 Betriebsanleitung Seite 78

Fig. 3.5: Process control example: TopControl with sensor
3.2.1 Working of the positioner as position controller (Fig. 3.6)
The actual position (POS) is measured by the displacement measuring system. This position value is compared to the normalized
position setpoint signal (CMD). In cases of difference (Xd1), a voltage pulse-width modulation signal is sent as control signal.
With single-acting actuators, a positive error exists and pulses are sent from output B
error exists, and pulses are sent from output E
of the actuator and the setpoint is reduced 0. Z1 represents a disturbance variable.
CMD
Position
setpoint
Fig 3.6: Position control diagram
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to activate the exhaust air. With this system, the difference between the position
1
Xd1
Position controller
Position control
to activate the air supply. When a negative
1
B1
P
K
E1
Position Valve actuator
conctrol sole-
noid valve
POS
Path measuring system
Z1
Valve opening
Operating instructions no. 800607