Interested to Buy Any Domain ? << Click Here >> for more details...
Answer Posted / marmikjani
Why we use 4-20mA signal?? Not start from 0-03mA? & 20mA??
· We can not use 0-20 mA signal cos then it becomes very difficult to distinguish between "zero" signal and "instrument fail" signal.
· Where as if we use 4-20 mA. its very easy like when we get 4mA means the signal is at low level and if it is below 4mA it shows us that the instrument is not working or it is failed
•That may have been one of those arbitrary decisions that is sometimes made when a standard is developed. In addition to providing a non-zero minimum to allow detecting signal loss, the minimum signal voltage provides for a margin between the minimum signal and any noise that might be present. Perhaps someone determined that 4ma was large enough to help with noise and thought that the numbers worked out conveniently. A 16 volt difference between min and max, difference = 4 X min, range of 20% to 100%, perhaps seemed easier to work with than 17 volts, 5.67 X min and 15% to 100% or 18V, 9 X & 10% to 100%
•This 20 mA signal is not enough to trigger a spark and therefore we can limit fire hazards in plant area
•As there is a leakage current so 0 to 3 MA, so we consider as 4-20MA. But in some cases we will find some transmitters 0-20MA which are more costly than 4-20mA
| Is This Answer Correct ? | 1 Yes | 0 No |
Post New Answer View All Answers
why would you like to join our company
Which types of quections asked in interview for FORMULATION PLANT (PHARMA)
If a control valve is hunting means means if we are giving 50% to the cv, the cv will open at 51% then slowly slwoly it will reaches 49% , so what to do for solve this problem. The cv is double acting and mounted for anti surge operation, it having 4 nos. volume booster, one sov, one positioner, etc..?
what diffrence b/w plc s7200,300,400
what are procedure of sox-nox calibration
the pump holds on run indication into the dcs and filed local control panel remote push button condition operaton wrong like when the push button pushing conditions the pump is off and the push button release condition the pump is on totally opposite condition . And control room inside give the stop command into dcs just 1secon relay engage and again normal condition. How can I slove
ORP sensor working principle?
What you mean by multi stage control vavles?
Isometric drawings are generated during _________________ phase of a project
How to work temperature gauge?
In apron feeder how TPH is calculated?
HOW CREATED LP & HP PRESURES IN DRUM FOR DRUM LEVEL MEASUREMENT!
How to convert Differential pressure to flow in TPH
what is difference between HOT permit and cold permit
describe flow nozzel principle?
