why 4 to 20 ma? why cant some other range?

Answer Posted / g pravin

at 4-20ma with +24V power supply, no spark will be
generated.& 1 VDC at 4 mA of loop current and 5 VDC at 20
mA of loop current as per standard of analog i/o cards.
if we use 0 to 20ma instead of 4 to 20 ma then we can not
find actual position zero reference output, for example if
we have a motorized valve, it's full close at that time we
get 0ma (0%) reference and at fully open position we get
20ma (100%) reference, in this condition if power supply of
is off then we also get 0ma reference, so here in this kind
of
Condition we can't get actual result like that gate is
actually close or any other problems as per explanation of
above

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