Type.8793.With.process.controller.function; Type.8793.With.process.controller.function - Burkert 8792 Operating Instructions Manual

8. Type 8793 WiTh prOcess cOnTrOller
funcTiOn
If the positioner Type 8793 is operated with process controller function, the position control mentioned in chapter
7. becomes the subordinate auxiliary control circuit; this results in a cascade control. The process controller in the
main control circuit of the positioner has a PID function. The process set-point value (SP) is specified as set-point
value and compared with the actual value (PV) of the process variable to be controlled. 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 determined by the process controller. If there is a control
difference (Xd1), the actuator is aerated and deaerated via the control system. In this way the position of the actuator
is changed until control difference is 0. Z2 represents a disturbance variable.
CMD
SP
Process set-
point value
Fig. 5: Signal flow plan of process controller
26
Xd1
+ -
Position
controller
Position measuring system
position control circuit
CMD
Xd2
+
-
Process
controller
English
Z1
B1
P
K
E1
Control system
Continuous
Solenoid valves
valve
POS
Valve
position
opening
control
circuit
PV
Transmitter
Types 8792, 8793
Description of System
Valve opening
Z2
Process variable
Process