What is scan time of plc?& diff. between DCS & PLC?

[onkpat]

Pl. explain in details.
thanks.

 

[Unregistered]

Pl..... search some info on your own first. Then you can get some help about it.

 

[dchartier]

Hello Onkpat;

At the very least, open the Learn PLCs page available at the top of this website and read the available info. And you can also use the Search utility to find out if others before you have asked the same questions that you need to answer for your test/lab/exam.
Hope this helps,
Daniel Chartier

 

[Tom Jenkins]

First, you need to differentiate between scan time and communications latency.

Scan time is usually referring to the time it takes the PLC to scan its logic - the time it takes to go from the beginning to the end of the program and solve the logic and update I/O. A DCS doesn't usually have scan time issues, since the internal logic is quite short and standardized.

Communications latency is the time it takes the master, either a PC, a master PLC, or a mini-computer, to read and write the data to all of the devices in the system and be ready to repeat the cycle. This varies with baud rate, protocol, errors, etc. It doesn't really matter whether it is a DCS or a PLC network if all of the communications parameters are the same.