Why we are using 4-20 mA as Analog signal transmission
other than 3 to 19 or 2 to 18 or 6 to 22 like wise ? What
is the reason behind using 4 & 20 mA? Can anyone give
proper technical reply ?
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Answer Posted / vinoth
the destination of any signal will be a Controller.
Take DCS, its input supply will be 1-5V.
from instruments, across a 250ohm resistor, the value will
reach DCS as desired 1-5V.
expl:
say 4ma is the output of transmitter.
V=IR,
V=4ma * 250 ohm
V= 1V,
say 20ma,
V=20ma*250ohm
V=5V.
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