Operation As A Process Controller (Option); Example Of Process Control: Top Control Continuous With Sensor - Burkert 8630 Operating Instructions Manual

S D
YSTEM ESCRIPTION

* Operation as a process controller (option)

On operation of the TOP Control Continuous as a process controller, the abovementioned position
control becomes a subordinate auxiliary control loop; the result is a cascade control. The process
controller in the main loop of the TOP Control Continuous has a PID function. The setpoint specified is
the process setpoint (SP) and it is compared with the process variable to be controlled. The actual
position (XPOS) of the pneumatic actuator is measured via the position sensing system. The controller
compares this actual value of the position with the setpoint (CMD) , which can be specified as a
standard signal. If a control difference (Xd1) exists, a pulse-width modulated voltage signal is sent to the
positioning system as the correcting variable. With single-acting actuators, if the difference is positive,
the pressurizing valve is driven via output B1. If it is negative, the exhaust valve is driven via output E1.
In this way, the position of the actuator is altered until the control difference is zero. Z2 represents a
disturbance.
Xd1
SP
Process
setpoint
22 - 8630
B1
E1
Positioner Positioning
system Soleno-
id valves
XPOS
Position sensor
Xd2 CMD
Process controller
PV
Z1
P
K
Valve
opening
Continuous
Valve
Z2
Valve
opening
Process
Transmitter
Process variable