Burkert Type 8793 - Manual (Page 9)

9
Description of System
Type 8792, 8793
6 DESCRIPTION OF SYSTEM
6.1 General description
The positioner Type 8792 / process controller Type 8793 is a digital,
electro-pneumatic position controller for pneumatically actuated pro-
portional valves. The device incorporates the main function groups
- Position sensor
- Electro-pneumatic control system
- Microprocessor electronics
The position sensor measures the current positions of the proportional
valve.
The microprocessor electronics continuously compare the current position
(actual value) with a set-point position value specified via the standard
signal input and supplies the result to the positioner/process controller.
If there is a control difference, the electro-pneumatic control system
corrects the actual position accordingly.
6.2 Designs
6.2.1 Type 8792, positioner
The position of the actuator is regulated according to the position
set-point value. The position set-point value is specified by an external
standard signal (or via field bus).
6.2.2 Type 8793, process controller
Type 8793 also features a PID controller which, apart from actual
position control, can also be used to implement process control (e.g.
level, pressure, flow rate, temperature) in the sense of a cascade control.
The process controller Type 8793 is operated with a 128 x 64 dot
matrix graphics display and a keypad with 4 keys.
The process controller is linked to a control circuit. The position set-
point value of the valve is calculated from the process set-point value
and the actual process value via the control parameters (PID controller).
The process set-point value can be set by an external signal.
6.2.3 Type 8793 remote operation with
external position sensor
In the case of this model the positioner has no position sensor in the
form of a rotary position sensor, but an external remote sensor.
Depending on the connection type of the path sensor,
Type 8793 functions as a process controller or positioner
(position controller)
The following connection options are possible:
Function Interface Sensor Setting in the menu
(ADD.FUNCTION)
Process con-
troller Type
8793 digital
(serial) Remote Sensor
Type 8798 POS.SENSOR
→ DIGITAL
Positioner
Type 8793 analog
(4 ... 20
mA) * Any, high-
resolution path
sensor POS.SENSOR
→ ANALOG
Tab. 1: Connection options Type 8793 with external position sensor
* If the path sensor is connected to the process controller Type
8793 via the analog interface, it can be operated only as a
positioner (position controller).
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