why we r using 4-20ma instead of 0-20ma in instrumentation

Answer Posted / nithi

This is to discriminate the wire-break of sensor and the
zero value of measured parameter.
ex:If pressure transducer measures 0 bar pressure,it will
send 4mA signal to the monitoring unit(EX:PLC).in case ,if
there is any break(dis-continuity) in wire then PLC senses
the 0 mA and gives alarm or shutdown depends on the
important of that parameter.

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