Chapter 5. SCADA Technology

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

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