1,why we use 4-20 ma output of all instrument qhy not use 0-
20,
2,what is the different between PLC & DCS.
3,how can we meaure maximum span of new flowmeter if not
given any information.

Answer Posted / rohan g

0 to 20 vdc signal may detoriate over distance but current
signal will remain intact.
noise will not affect current signal at all but vdc signal
will get affected.
if equipment fails then also it gives 0 vdc signal in case
of 1 to 20 vdc.but not in case of 4 to 20 ma.
DCS can be viwed as bigger version of PLC.Since no i/p dcs
can support is more in case of dcs.Also dcs can have
operator interface but plc dosent have such.

Is This Answer Correct ?    17 Yes 5 No



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