Process controller type 8793, Process.controller.type.8793 – Burkert Type 8793 User Manual
Page 23

23
Description of System
9.
PROCESS CONTROLLER TYPE 8793
In the case of process controller Type 8793 the position control mentioned in Chapter “8” becomes the subor-
dinate auxiliary control circuit; this results in a cascade control. The process controller in the main control circuit of
Type 8793 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 sensor records the current position (POS)
of the pneumatic actuator. The positioner 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.
Valve opening
Continuous
valve
Control system
Solenoid valves
Position sensor
Positioner
CMD
Xd1
B1
E1
P
K
Z1
POS
Position control circuit
+ -
Process variable
Process
Transmitter
Process
controller
Process set-
point value
SP
Xd2
CMD
Valve
opening
Z2
PV
+
-
Position
control
circuit
Figure 5:
Signal flow plan of process controller
English
Types 8792, 8793