why do we use 4-20mA as o/p and why don't use 0-20mA or 5-
21mA?

Answer Posted / d tilston

Two wire transmitters require some power to work. 0-20 mA
would not provide any power at 0 mA.

Power = current x volts, (usually 24 VDC)
Power = 0.004A x 24VDC
Power = 0.096W

Not much power.

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