Chapter 5. SCADA Technology

Table of Contents
General Definition
Building Automation
SCADA vs DCS
SCADA Future
Process simulator
Reliability and hot standby
Protocol converter
SCADA HMI Input Devices
References

General Definition

Re: Definition

Wed, 22 Jan 1997 15:31:00 +0000

Bernard, My working definitions are as follows: SCADA - uses MMI to present the data acquired from the process to allow the process's operation to be supervised e.g. Start/Stop or changing setpoints. Typically a SCADA system consists of a PC with a SCADA package connected serially to a PLC. A DCS (Distributed Control System)can also be considered to provide SCADA functionality. However, a SCADA system is not necesarily a DCS. One can argue about the definition of distributed control system but the issue can get cloudy depending onthe vendor you talk to. For example is a number of networked PLC's and PC SCADA systems a DCS? Ignoring the traditional use of the term DCS the answer is Yes. Please don't get caught up with the fact that SCADA has been more traditionally applied to a system that uses some form of radio or leased line communications to get the data from the 'process'. Batch Control Systems - a specific application that could be developed on a PLC or DCS to handle batch process automation. Softlogic - This is a bit of a misnomer as PLC code is softlogic as is DCS code. The PC based tools around that allow control schemes to be performed on a PC. It is not a term I would use. SCADA Software is a software package that usually comes with a single driver of your choice from an extensive list. It does not include the PLC. SCADA provides MMI functions such as: Mimics - A graphical representation of the process with dynamically updated values. Trends - Graphs of variables against selected time periods Reports - Allows process variable to be summarised on a periodic basis Alarms - provides presentation of process alarms In addition there is the data acquisition and the facility to enter required changes back to the process control hardware. Hope this helps. Shaun

Ref: c:/emacs/definitions/msg00003.sgml