Instrumentation Interview Question:

Why 4-20 mA signal is preferred over a 0-10V signal?

Submitted by: Administrator

Generally in a transistor some amount of voltage is required for turning it on. This voltage is the cut in voltage. Up to this voltage the exists a nonlinearity in its characteristics. Beyond this cut in voltage the char. of transistor is linear. This nonlinear region lays between 0-4ma, beyond 4ma it linear. This is why 4-20 ma range is used.
Submitted by: Administrator

One reason is we can get the most linear characteristics in this range.The second one is if the signal is to be send to long distances,current signal is preferable,because a voltage is subjected to losses due to resistance of the long wire used for transmission.
Submitted by: Vivek Narayanan

because our loop is in series and voltage drop in series but current is not drop in series then current prefer to voltage
Submitted by: Waseem Abbas