Y to use 4 to 20ma instead of 0-10v

Categories >> Engineering >> Instrumentation
Suggest New Category

Question Posted / sathish

5 Answers
9416 Views
I also Faced
E-Mail Answers

Answers were Sorted based on User's Feedback

Y to use 4 to 20ma instead of 0-10v..

Answer / ravinder

Because Voltage drops as resistance of cable conductor
increases but current will be same at any point of the
loop.4mA is called Live Zero,shows liveliness of the loop
when process variable is zero.

Is This Answer Correct ?

27 Yes

4 No

Y to use 4 to 20ma instead of 0-10v..

Answer / jaldeep

For signal transmission we are using 4 to 20 mA, because of
following reasons.
1. If you are using 0 to 10 for long distance then
signal will be dropped due to cable resistance you will not
get correct feedback
2. 4 to 20 mA will give correct feedback even for
long distance. It will not drop according to cable
resistance. Only you have to keep loop impedance as per
your field instrument.
3. Open loop, you can easily detect in 4 to 20 mA.
You can program if mA is less than 4 then you can define it
as open loop.
4. For 0 to 10 v input if cable is open then it will
be difficult to identify that cable is open or input is 0
volt.

Is This Answer Correct ?

17 Yes

0 No

Y to use 4 to 20ma instead of 0-10v..

Answer / himanshu

beacause total loop resistence is 250ohms.
so 24VDC supplied loop 1v corresponds to 4mA
and 5v corresponds to 20mA.
HART PC communicates to 1-5VDC only.
As explained in above answer 4mA is LIVE ZERo.
for 20mA reason is above 20mA current can be hazareous for
fieled.(fire).like HC and Refineries
thats why 20mA signal is used.

Is This Answer Correct ?

9 Yes

4 No

Y to use 4 to 20ma instead of 0-10v..

Answer / ecxlsync

current signal is used because as explained
it will not change even the loop resistance is changed
due to transmission lines resistance. it is stated in the KCL that current entering in the circuit will be equal to the
current leaving no matter if the circuit resistance is changed.

Voltage signal is greatly affected by the circuit resistance.
long distance transmission has large wire resistance that
will cause large voltage drop.

Is This Answer Correct ?

1 Yes

0 No

Y to use 4 to 20ma instead of 0-10v..

Answer / kalpesh

Because if we use 0-10V signal and if there is a break in
cable loop then it will show 0V which is the low level of
the measured signal but in reality it is a signal failure
from transmitter.

Is This Answer Correct ?

4 Yes

4 No

Post New Answer

More Instrumentation Interview Questions

model question paper of instrumentation for Jindal GET 2010.plz reply sudhanshukumar08@yahoo.com

0 Answers Jindal,

I wnat to practice more online type questions .so will you show them me to take a practice test?

0 Answers VA Tech Wabag,

what is plc? Basic function of plc? application of plc in industry? What is lader diagram ? What is the main advantage to use plc in industry?

15 Answers Schlumberger,

What is difference between converter & transducers?

4 Answers

Draw block digram for well head from well to shipping pump?

0 Answers

Explain Difference between Bech set and operating range of control valve

3 Answers

what is beta ratio?

3 Answers

Can anyone help me with the Question bank(objective type) for complete Instrumentation engineering,either a soft copy or a Hard copy(Book),or the name of the author ,or publisher.

1 Answers Reliance,

What is the difference between rich gas and lean gas?

3 Answers

What is megering????

2 Answers

To find closed tank level by DP transmitter , how to findout its range.and insomeplace they using range like - 1500 to +1500 mmwc why not 0 to 3000 mmwc. how they spilit they range for minus and plus.and why?

1 Answers Kuwait Oil Company,

what are the on/off valve precaution?

1 Answers Reliance,

For more Instrumentation Interview Questions Click Here