why we take 4 to 20 mA as out put of every instrument like
pressure transmittre ?why we cant take 0 to 20mA as output?

Answer Posted / haridass (kwt)

Including the above answers the reason for selection of 4-
20mA for the transmitter signal is, the LINEARITY.

From 0-4mA the signal will not be much linear (in graph we
can come to know),

from 20+ mA is the indication to conclude that the
measuring signal is above to its range or loop fault.

Only from 4-20 the mA signal is with perfect slope.

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