Answer / abhishek

Main difference between DCS and PLC is about the scanning
time. PLC's have a fixed scanning time whereas DCS
execuation order(scanning) can be varied with certain
minimum limit. Generally a PLC can have a scan rate of as
low as 5msec(fixed) to some where around 20msec(fixed). As
DCS handles larger number of inputs/outputs its scanning
rate is 50msec and this value needs to be defined (can be
kept more than 50msec) while writing a program. But latest
DCS can have scanning rate of 20msec.

Answer / vijay

Scan time is time required for checking i/p,to executive
program and give out put.generally 5msecfor plc

Answer / raja2016

time taken for 1 scan sequence ::

Housekeeping -I/P update - Program execution - O/P update - Programmer windows - System communication window - Housekeeping

Answer / abu maryam

scanning time:
In general: scanning time: it is the time taken to read all inputs then execute the program and apply on outputs.
In PLC: it is only 1 processor check the previous procedures so its scan time depend on the quantity of data and program.
In DCS: There are several processors each processor has its inputs and outputs and its private program so each processor in DCS has its private scan time applied on each loop.

Answer / srikrishnan

SCANNING TIME OF PLC DEPENDS ON THE NUMBER OF RUNGS, JUMP
COMMANDS, SUB ROUTINES, AND INTERFACING DRIVER
CONFIGURATION. THERE IS NO FIXED SCAN TIME FOR PLC.

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