DESCRIPTION

Technical Description

Field bus technology plays a key role in modern-day process automation. The field bus permits networking of terminal devices such as controllers, sensors or actuators in the plant system (field level) with the higher-level control room (control level). A network of this kind can be quite extensive; line lengths of as much as 1000 metres and more are possible.

This experimental unit is used to teach the initial basic steps in field bus technology based on the example of Profibus DP. Various terminal devices (slaves) are activated and read by a PC with a Profibus DP interface (master). The required hardware is largely pre-configured. Students are able to concentrate on the software programming of the field bus system. The following specific topics can be covered: System configurator with DMF (Device Master File), bus topology, communication protocols, tags, OPC (OLE for Process Control) server, input and output of process data, and much more.

The experimental unit includes a digital controller as well as analogue and digital input and output modules with a Profibus DP interface. Two potentiometers permit the simulation of input signals for the controllers. A digital voltmeter displays the output signals. Digital signals are generated by switches and displayed by LEDs. The controlled variable, manipulating variable and reference variable data are delivered as standard signals at lab jacks, enabling the controllers to be incorporated into real processes at any time.

The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.

Learning Objectives / Experiments

- function and programming of a field bus system
  * defining the bus topology with the stations
  * writing the communication protocols
  * familiarisation with the device master file
  * familiarisation with the OPC server
  * defining tags
  * accessing the OPC database from a process control program
- familiarisation with the field bus stations  
  * function of a digital process controller
  * function of an analogue input / output module
  * function of a digital input / output module