Answers were Sorted based on User's Feedback
Answer / sunil kumar
Before using 4 - 20 mA all most of the instruments were
using 0 - 20 mA but after some problem faced for
finding "live zero", it was changed to 4 - 20 mA. By live
zero I mean when the instrument is connected but with 0
process value, the current is 0 mA, & the same current
value is seen when there is a cable damage or no power. By
this it was difficult to find the live zero. After that it
was changed to 4 - 20 mA. 4 - 20 mA Why? why not 5 to 20 mA?
The reason is that most of the a to d convertor which is
capable of providing 1 - 5 VDC with 250 ohms the same
current could be used as per below.
4 X 250 = 1 V DC & 20 X 250 = 5 V DC.
|Is This Answer Correct ?||78 Yes||8 No|
Answer / gurpreet chahal
we use 4-20 ma to achieving maximum linearity ,and another
tning safety point of view no spark can genrate up to 20 ma.
|Is This Answer Correct ?||4 Yes||0 No|
Answer / therion
for eg. if we are monitor a flow tube and measure the rate
of flow through the tube or pipe then 4mA will represent
ZERO flow and 20mA maximum flow..if it drops to below 4mA
then it shows reverse flow (which is not good)
|Is This Answer Correct ?||3 Yes||3 No|
Answer / sandeep bisen
due to achieving maximum linearity in between 4- 20 ma.
|Is This Answer Correct ?||9 Yes||11 No|
what is difference between neutral and earth
WHAT IS THE MEANING OF CYWY
I Want randstand placement papers
what is the healthy specific gravity of lead acid battery used in DG sets ?
how the 3phase induction motor is running in 2phase supply with help of capacitor?
How to convert 2 phase to 3 phase electricpower in induction moter?
If i want to build 230kv substation what are the equipments to be installed?
What is the reason behind 11kv 33kv 132kv.....means multiple of 11?
can we use transformer for 70 Hz?
Difference between divercity and power factor
When generator connected, the circuit ELCB exploded. What is the reson?
how steam converted into electricity in power plant