why can't we use 5-20mA standard or some other instead of 4-
20mA?

Answer Posted / mohammed abbas

4 - 20 ma is used because one resion is that control system
like DCS AND PLC will accept (1 - 5vdc)only for that resion
by connection 250 ohm resistand accross with ( 4 - 20 ma)
we can get ( 1 to 5 vdc) (1vdc=4ma and 5vdc=20ma) this is
as per ohms law ,V=IR
IF V=4ma*250ohm=1vdc
20ma*250ohm=5vdc
(4 - 20)ma is linear with(0 -100%) and the output will get
linear from 4ma,

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