Answer Posted / eid elatawy

PLC is a programmable logic controller which take the inputs from the system and execute it through the program written by Ladder or STL (statement list)language and provide the output to the system.the famous CO Siemens,Allen Bradly.

DCS is distributed control system the same idea for PLC for take the input and execute it through the program to provide the output.the famous CO Yokogawa,Honeywell


We can enumerate the difference as following:-
PLC
1- no of points less.and almost of these points digital points.
2- no of analog points very less.
3- trends and history not allowed.
4- used for machines and separate units with HMI and in this case called SCADA system.
5- cost is less and easy to make extension.
6-scanning time less.

DCS
1- you can use more than 10000 points
2- no of analog points more.
3- trends and history allowed and saved in server for along time.
4- used for a big plants like oil&gas-chemicals and petrochemicals..
5-cost very high and you have to min cost of the system + no of points separate. so the extension not easy like PLC
6- Scanning time more than PLC.
7- We can monitor the all inputs and control all outputs

Regards

Eid Elatawy
I&C Engineer
TCI sanmar chemicals CO
Port said
Egypt
contact no- 002 01000470262
mail- eng.eid72@gmail.com

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