why we used for range in pnumatic 3-15 psi and current 4-20
ma?

Answers were Sorted based on User's Feedback



why we used for range in pnumatic 3-15 psi and current 4-20 ma?..

Answer / saravanamurthy

Hi,

4-20 mA standard is mainly to differentiate the conditions
live zero and dead zero i.e let me tell an example consider
a level sensor fixed in a tank . now the tank is empty .
then the sensor will send the reading as 0mA this zero is
live zero, if there is no standard as 4-20mA. in the same
case if there is any problem in the sensor output then also
the reading ll be 0mA this zero is Dead zero.In order to
differentiate the fault and the original process condition
we have chose this range as the standard.

Thanks & Regards,

S.I.Saravanamurthy.

Your comments are welcome

Is This Answer Correct ?    101 Yes 14 No

why we used for range in pnumatic 3-15 psi and current 4-20 ma?..

Answer / pankaj kumar

because in b/n 3 to 15 psi the responce of actuator & control
valve is linear.before this hunting problem occurs.
we use 4 to 20 ma signal as standard signal because during
confurigation of hart 250ohm resistance or connected that is
easly converted in to voltage signal.(1v to 5v )......
instead of voltage signal current signal use because voltage
is pickup noise more as compare to current.
and in case of voltage signal chance of voltage
droff...............

Is This Answer Correct ?    19 Yes 5 No

why we used for range in pnumatic 3-15 psi and current 4-20 ma?..

Answer / gunasekar.man

because it is use for voltage drop 4-20ma pnuematic input supply presure 6bar will be converted to be 3-15 psi are also its standrd use.some application will be use diffrent power supply for 5v,12v,24v.....but 4-20ma are constant

Is This Answer Correct ?    6 Yes 2 No

why we used for range in pnumatic 3-15 psi and current 4-20 ma?..

Answer / lomesh vadhankar

For 4-20mA, the linearity scale comes proper, as well as if
we want to convert, 4-20 mA than its easy to factorize, in
range of, 0-25%,25-50%,50-75% and 75-100%.. So, If suppose,
any control valve is needed to control, then it will be
easier to control it... And for other reasons, as
Mr.S.I.Saravanamurthy Perfectly said, is the ZERo zone. so
that, the Dead condition of any instrument can be
differentiated from normal Zero parameter condition.

Thank you..
Your comments are welcome

Lomesh Vadhankar

Is This Answer Correct ?    10 Yes 9 No

why we used for range in pnumatic 3-15 psi and current 4-20 ma?..

Answer / saravanamurthy

Justification Steps:

1. Interpolate the coordinates of % opening and Current in Y-axis and X-axis Respectively

2.Connect the coordinates , you will get a straight line

3.Since it is with slope , it's our responsiblity to calculate the slope so that we can project it in normal plane
Slope Calculation:
a.Equation of straight line : Y=mX+C

where,
Y- Current in mA
X-%opening of full scale
m-Slope of the straight line
C- constant (calculated from Y intercept )

b.Calculate Slope using the formula:

m=(X2 - X1)/(Y2 - Y1 )

4.In this range of current , the value of slope is found to be constant , ie.m=0.16, but when we go for some other ranges slope changes as it ascends so its non linear for other ranges.
5.finally straight line equation for the above range is Y=0.16*X+4
6.This constant slope means that the line is linear


Regards,

S.I.Saravanamurthy

Is This Answer Correct ?    4 Yes 5 No

why we used for range in pnumatic 3-15 psi and current 4-20 ma?..

Answer / biju antony

The transmitter output stance from what is known as "live zero". This system has
specific advantages :
1. The systems automatically alarms when the signal system becomes inoperative.
2. The output areas is linear ( Ratio of 1 : 5 ).
DEAD ZERO SIGNAL :
The advantage is that it does not have to be biased to true zero. A "Live zero" gives the
computer additional information, so that it can takes appropriate alarm action in case of a
measurement failure, because it can discriminate between a transmitter operating, but
transmitting a zero measurement and a failure, in the signal system.

Is This Answer Correct ?    4 Yes 6 No

why we used for range in pnumatic 3-15 psi and current 4-20 ma?..

Answer / yashpal

i want to add just one thing that above mA there will be a
electromagnetic interference and signal may be distort due
to that.

Is This Answer Correct ?    1 Yes 4 No

why we used for range in pnumatic 3-15 psi and current 4-20 ma?..

Answer / vivek jain

why not 0 to 3 mA becoz the output is nonlinear.(also live
zero(if it is a process variable)and dead zero(if there is
wire break))
4-20mA the output is linear.
also 20 is a multiple of 4 i.e why 20mA!
IF THE OUTPUT GOES ABOVE 20 mA THEN THERE IS UPPER LIMIT
VIOLATION I.E THE OUTPUT WILL REMAIN CONSTANT AT 20.5mA.

Is This Answer Correct ?    1 Yes 5 No

why we used for range in pnumatic 3-15 psi and current 4-20 ma?..

Answer / rawjaw

Previous ans is right. But also
refer the answer posted by
others asked same question
by ONGC exams for the very
best answer

Is This Answer Correct ?    1 Yes 6 No

why we used for range in pnumatic 3-15 psi and current 4-20 ma?..

Answer / mdshafiullakhan

why we should use for range in 3-15 psi and 4-20ma because
the linearity curve will starts from 4-20ma only during this
source range only we will get the linearised output that is
the reason and 0.22 psi to 1 kg the process will begins from
0.22 to 1 kg

Is This Answer Correct ?    8 Yes 23 No

Post New Answer

More Instrumentation Interview Questions

1)How many tpes of vibration probe and how many tpyes of vibration. 2)how we can calibrate a vibration probe with tk3 3)what is RMS value in vibration measuring application and how we calculate it.

0 Answers  


the output of the common trasmitter protocol in qatar gas are the following

0 Answers  


How to calibrate electronic type level switch low?

1 Answers  


what is SIL 1 2 3

0 Answers   KOC,


send me last 5 years questions asked in rrb chennai, for section engineer

0 Answers   RRB,






is here anybody who knows how to calibrate the pressure transmitter? ONLINE

5 Answers  


in the pipe line if the control valve fails to respond to controller action,by what means we can stop the flow in the pipe line ?

9 Answers  


why orfice is not used for main steam flow calculation

0 Answers   OEG,


what is function of PLC, and how is it work , explain with difination

1 Answers   Bapco Bahrain Petroleum Company,


How much voltage we get between two wire of 4 to 20 ma output? Is this voltage up or down respectvice to 4 - 20 ma ?

9 Answers  


Determine the manipulated variable, controlled variable, and the measured variable given a description of various typical industrial processes.

6 Answers   Honeywell,


what is gas metering system? gas chromatograph? and gas compressors?

0 Answers   HPCL,


Categories
  • Civil Engineering Interview Questions Civil Engineering (5084)
  • Mechanical Engineering Interview Questions Mechanical Engineering (4451)
  • Electrical Engineering Interview Questions Electrical Engineering (16631)
  • Electronics Communications Interview Questions Electronics Communications (3918)
  • Chemical Engineering Interview Questions Chemical Engineering (1094)
  • Aeronautical Engineering Interview Questions Aeronautical Engineering (239)
  • Bio Engineering Interview Questions Bio Engineering (96)
  • Metallurgy Interview Questions Metallurgy (361)
  • Industrial Engineering Interview Questions Industrial Engineering (259)
  • Instrumentation Interview Questions Instrumentation (3014)
  • Automobile Engineering Interview Questions Automobile Engineering (332)
  • Mechatronics Engineering Interview Questions Mechatronics Engineering (97)
  • Marine Engineering Interview Questions Marine Engineering (124)
  • Power Plant Engineering Interview Questions Power Plant Engineering (172)
  • Textile Engineering Interview Questions Textile Engineering (575)
  • Production Engineering Interview Questions Production Engineering (25)
  • Satellite Systems Engineering Interview Questions Satellite Systems Engineering (106)
  • Engineering AllOther Interview Questions Engineering AllOther (1379)