Answer / maiatec

The main reason is that the current 4-20mA can reach long distances without loss of information. The current does not alter because it is a loop without derivations. Moreover, with the voltage of 0-10V can not reach long distances due to voltage drop on the resistance of the wire.

Answer / hari krishna

the signal are transmitted from the field to the
controlroom and vseversa through cables. for long
transmission the cable resistance increases.thus if 0-10v
are transmitted over this long distance,due to the
resistance of cable there will be drop in the voltage and
the signal received at the controlroom will not be
accurate. to overcome this difficulty 4-20ma signal is used
for transmission.

Answer / ribin

while transmitting current there is a less drop, while
transmitting as a voltage more drop occurs. so prefer 4-20mA

Answer / swagat pundpal

For detecting open loop we need non zero current ie "live zero".
For transmitters min 3mA current is needed to turn it ON.
so 3mA + safety factor (1mA) =4mA

Within 4-20mA range, get good linearity, also one more reason is if more than 25mA current flows through human heart hi dies so safety point of view 20mA.

Answer / shafqat khan

when 0-10 v will b use in the transmission line the out put
value will b not correct bcz of voltage drop due to resistance
and the 0 which is used win case 0f v signal can b effect
in case of input fault we can,t find the input fault as well
as the o/p value will b also effected.....

Answer / pooja

becoz in 0-10 v there is voltage drop due to increase in resistance ( due to increase in length) that us why signal obtained is not accurate

Answer / satishpatel

generally in a transister some amount of voltage is
required for turning it on. this voltage is the cutin
voltage. up to this voltage the exists a nonlinerity in its
charecteristics. beyond this cutin voltage the char. of
transister is linear. this nonlinear region lies between 0-
4ma,beyond 4ma it linear. this is why 4-20 ma range is used.

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