Answer / ali abideen ,,

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.

Answer / anil

starting with 4ma is to know DEAD or LIVE of the
transmitter,4 to 20 is used for linearty and according to
ohms law to covert 1 to 5 volt dc,

Answer / ravi vaya

Because 4 mA is called live zero of transmeter
If we set 0 mA at 0 pressure ya any ,we can`t deside inst.
is working ok .

And also mA is be a linear from 4 mA

Answer / lalatendu keshari prusty

4-20ma signals will travel along distance without dropping signal value and the internal circuit distinguish between connection break & minimum value.

Answer / mike betts

I am not sure why the range of 16mA i.e 20 - 4, but the 4mA
starting is so that you have a posative value of current for
all values that the loop current represents. This way, if
you have no current at all, the loop is open circuit for
some reason.

Answer / vanapalli rajesh

because 4-20ma is a linear range compared to other ranges

I am manjunath having exp in maintenance of chemical plants,know i want to do a design course INTOOLS,after doing design course can we get jobs in design field.sinve i dont have design exp..

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Dear sir I am MD.zafar eqbal. I have taken this id from allinterwiev .com I have qustion if you dont mind. 1.what is the maximum operating temprature in instrumentation. 2. I want know about viberation i mean wahat types of sensor used in viberation And what types of trabsmitter used.and hiw to control it and wher is used of viberation transmitter and finally how to control it and what types of fault come. Sorry for disturbing you. I know you have no reason for help me. Because you dont know about me.but i request you please help me these question are very usefull for my feauture.plz sir Thanking you. Sent from Yahoo! Mail on Android

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