Difference between SCADA system and DCS system

[rj061991]

hi!

i am quite confused about SCADA and DCS.. is there any differences between the two systems?.

thanks for the info..

 

[Brendonh]

Brace yourself for a lot of differing opinions.

in my opinion they have become basically the same thing now days.

some will argue that SCADA is by very defination more aimed at data aqcuisition and alarming, and less about controlling machinery like a DCS.

but when you link a scada to a plc you pretty much have a DCS in my opinion.

 

[GeoffC]

is there any differences between the two systems

fro one - the cost
but seriously a DCS is a more tightly integrated control and monitoring system than with a plc and SCADA system.

 

[Tom Jenkins]

To me, in current usage, DCS and PLC are the business ends - the I/O and the control. SCADA is the human machine interface, usually PC based.

 

[rj061991]

ok. thanks you for the informations... it enlightened me about the differences between the two..^_^

 

[jraef]

Here is how it was taught to me years ago, it still rings fairly true even though the lines are more blurry.

A PLCs is used in machinery to make things, fast and accurately using primarily digital IO with some analog. Think thousands of relays interacting with each other, and a few loop controllers.

A DCS is used in a processing facility to make stuff, consistently and repeatedly using primarily analog IO with some digital. Think thousands of PID loop controllers interacting with each other and a few relays.

A SCADA system watches "big picture" activities happen over a wide area, makes sure it happens safely and that everyone involved knows about it, using stand alone small PLCs or other local loop controllers as field interface devices talking to a central user interface. Think dozens of individual pump control panels acting independently on local conditions, feeding sewage to a treatment plant while talking to a central system that is coordinating their activities.

 

[danw]

Great summary statements, Jeff.