Answer / naveen

Logically Zero milli amps means no current in the circuit .
if we have an initial value to be measured , we cant measure
it as zero milli amps . It means no current in the circuit
or the circuit is open . so we go for the span of 4 to 20 mA
. this is coz we can easily split 4- 20 as multiples of four
(4,8,12,16) which means 0%,25%,50%,75%and 100% respectively.

Answer / sanjay sojitra

The live-zero represented by 4 mA allows the receiving
instrument to detect some failures of the loop, and also
allows transmitter devices to be powered by the same
current loop (called two-wire transmitters)

Answer / nirmalya basu

In both of the measurement 20ma represents full data and 4ma
or 0ma shows no data.But with 0ma we cant diagnose the wire
breakage in the transmission line but with 4ma we can diagnose
because if this type of fault is occurred then it shows
0ma.Thats why 4 20ma is used.

Answer / shshiki

logic zero is show no current in circuit but we use 4 mili amp for instrument is on and ready for use and lower 4 mili amp current relation with non linear ..

Answer / vikash tiwari

4-20ma is a linear system.
Live zero system used in loop so 4-20ma use.
Various instrument use in a loop,when one instrument is faulty so not required to check all loop instrument in live zero system.

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