Current does not have any drop during transimission through 
electrical wires however the voltage drops as the lengh of 
elecrical wire used for transmission increases.
Thats why mA is preffered over mV etc.

  MA IS PREFFERED THERE IS NO DROP IN CURRENT.SO ONLY MA 
IS  PREFFERED

most probably mA signal is preffered in signal transmission 
because the voltage in the cable may be affected by the 
sidewise power cables which are running with this cable   
(in the same cable tray).

as we know  voltage is  noise sensitive ..so if transmission
is in the form of voltage then ll loose the original signal
nd at the reciever side ll not get accurate reading  ,,but
in d form of current  ..its not affected by noise

mA Signal :-

1. Current measures remain same in any point of the signal 
transmission line(no loss).
2. Less noise interference.

mV Signal:-

1. Voltage droup occurs(loss).
2. Noise interference is high. 


So that mA signal is preferred over mV signal

mA is the ideal analog signal to be used because it has no 
voltage drop. The same current will be recieved  even in 
100m transmission line.
Voltage signal is much accurate than mA but it is good only 
for short range application because of its characteristics. 
Prone to noise and voltage drop.