Answer / jb

In long distance wire if some wire are broken then at the
receiver end there will be current value 0. If we take 0-20
standard in that case it will be difficult to know that the
current value is actually 0 or its 0 because of broken wire.
but in case of 4-20 it the the signal is in off state then
at the receiver end we will have current value 4 and in
case of broken wore we will have current value 0.

Answer / bhanu prabhath

yes, i agree with JB,s answar, to some exctent, some times transmitter 0 drifts due to calibration disterbance,if we use 0-20ma we cont find the -ve 0 drift of the transmitter in case of 4-20 the drift will be within the 0-4ma. also the 4-20ma is easy to equal division and calculate with any range .

Answer / parag pathak

Signal can be sent via voltage, but as signal will be drop
if it has to sent long distance,but current signal will not
not lost,so we are preffering current signal over voltage
signal. secondly we can use 0-20 mA instead of 4-20 mA, but
then we cannot know whether it is dead zero or 0 reading.
Now once any manufacturer make any standard it is accepted
throughout so that new Instrument will also be compatible
with that system.

Answer / charankumar

We are using 4 -20 ma because we will get linear current
with respect to 24 V,so i most of cases 4-20ma is used.
If u want to try plese plot a graph and check.

Answer / muthu

in communication, some loss occurs . if we sent 0-20 mA
signal through comunication, 0-4 mA vanishes due to loss.
so 4-20 mA current signal are preferred in standard.

Answer / anwar azim

Other communication methods suppose RS232 are having
constrains for long distance communication and require
repeater after some distance and are prone to external
disturbances.4-20mA is not prone to external disturbances
and the cabling can be done for long distances with out any
effect on signal.

i have an interview in Qatar Petroleum. So please provide the all details abt fire & gas systems

1 Answers   Qatar Petroleums,

What is the role of integral in PID controller

3 Answers  

is motorized valve closed when power shutoff?

0 Answers   Unilever,

generally transmitter power supply having some range(12v to 35v) but the out put(4-20 mA) must same for given input.If we vary the power supply voltage then output mA also to be change according to V=IR. Is there any voltage regulator in the transmitter ?

2 Answers  

Explain operation of Haskel pump.

0 Answers   CCIE,

What is the difference between a Extension cable and a copnesating cable.Where can we use compensating cable. Is anywhere compensating cable are used for mv transmission to the indicator.

1 Answers  

how can i calibrate E & h make conductivity transmiter . unit : mocro siemens Range :0 to 100 micro siemens sensor : capacitive type

1 Answers  

Exapain Deatails of the PID controlller

4 Answers  

The wire is disconnected from the temperature sending unit (magnetic gauge). A voltmeter connected to the wire reads 0v. What does this indicate?

2 Answers  

CAN WE CALIBRATE LEVEL TRANSMITTER USING HART COMMUNICATOR WHEN WATER LEVEL IS PRESENT IN THE BOILER SHELL?

4 Answers   Chemin, Emerson,

How to convertion 100 m3/hr to mmH2O or to Kg/cm2?

0 Answers  

why we use the ac supply load cell>?can we use the dc supply load cell?advantages and disadvantage of the ac supply load cell?

0 Answers