Burkert Type 8791 - Manual (Page 12)

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Description of System
5. DescripTiOn Of sysTem
5.1. general description
The positioner Type 8791 is a digital, electropneumatic position controller for pneumatically actuated proportional
valves. The device incorporates the main function groups
- Position sensor
- Electropneumatic 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 position controller.
If there is a control difference, the electropneumatic control system corrects the actual position accordingly.
5.1.1. features
• version
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.
• position sensor
- internal high resolution conductive potentiometer or
- external non-contact, non-wearing position sensor (remote).
• Microprocessor-controlled electronics
for signal processing, control and valve control.
• control module
The unit is operated via 2 keys and 4 DIP switches.
3 LEDs indicate the status of the unit.
• control system
The control system consists of 2 solenoid valves and 4 diaphragm reinforcers. In single-acting actuators the
working connection 2 must be sealed with a threaded plug.
• feedback (optional)
The feedback is implemented either via 2 proximity switches or via an 4 – 20 mA output.
The operator can change the proximity switches or limit positions via control lugs.
• pneumatic interfaces
Internal thread G1/4“
• electrical interfaces
Circular plug-in connector or cable gland
• communications interface
For configuration and parameterization
• housing
Plastic-coated aluminium housing with hinged cover and captive screws.
english
Type 8791