Thursday, June 18, 2009
Interview Question: Why SCAN time of DCS is more than PLC? or Why does PLC have scan time less than DCS.
If so,then why do we use DCS instead of PLC?
My Interview Answer:
Scan time of DCS is more than the scan time of PLC when the I/O's are digital.Whereas the scan time of DCS is less than the scan time of PLC when the I/O's are analog.Hence DCS is better when analog signals are considered whereas PLC is better when digital signals are considered.However DCS do handle both analog and digital signals. It can also have more no. of I/O's compared to PLC.About 1 lakh I/O’s are available in DCS. Hence we use DCS.