Process.controller.type.ep.501.C; Process.controller.type.ep.501.C - EBRO ARMATUREN EP 501 C Operating Instructions Manual

Typ EP 501
Description of System
9. PROCESS CONTROLLER TYPE EP 501 C
In the case of process controller Type EP 501 C 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 EP 501 C 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.
CMD
+ -
Xd2
SP
+
-
Process set-
point value
Figure 5: Signal flow plan of process controller
B1
Xd1
E1
Control system
Positioner
Solenoid valves
POS
Position sensor
Position control circuit
CMD
Position
control
circuit
Process
controller
PV
Transmitter
Z1
Valve opening
P
K
Continuous
valve
Z2
Valve
opening
Process
english
Process variable
21