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hiteshpurani
Active Contributor

Join Date: Feb 2009
Location: india
Posts: 12

4-20mA

02/01/2009 7:43 AM

why we use 4-20mA range in current o/p or i/p. what is the reason for calibration zero at 4mA and span for 20mA
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lyn
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Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#1

Re: 4-20mA

02/01/2009 8:02 AM

This question was just asked and answered a few days ago.

If you look to the right, you'll see a "search this forum" window. Type your question in there.
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Anonymous Poster
#2

Re: 4-20mA

02/01/2009 5:06 PM

Don't feel bad hiteshpurani, I cant find it either
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Anonymous Poster
#3
In reply to #2

Re: 4-20mA

02/01/2009 6:33 PM

Please see this thread:

http://cr4.globalspec.com/thread/32389/standard
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betomachine
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United States - Member - New Member Engineering Fields - Chemical Engineering - New Member

Join Date: Apr 2007
Location: Austin, TX
Posts: 367
Good Answers: 10
#4

Re: 4-20mA

02/02/2009 8:41 AM

Hit the link, it will tell you the answer.

__________________
 Money doesn't talk, it screams in your face.
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michelle2480
Member

Join Date: Jun 2008
Posts: 6
#5

Re: 4-20mA

02/02/2009 11:36 PM

4-20mA range in current is used , since this range allows to transmit the signal effectively and also keeps the instrument device safe from any explosion/destruction.

in case if calibration is done at zero and a problem occurs in the device or the wiring it will not be detected since the system will assume that the instrument is working fine and showing 0mA thus to avoid this situation calibration is done at 4mA , since incase if the value goes below 4mA the system can detect the device is malfunctioning or there is some error in the reading
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