4-20mA Simulating vs Sourcing

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eltech Power-User Join Date: Mar 2011 Location: oz Posts: 252 Good Answers: 10	4-20mA Simulating vs Sourcing 07/28/2011 9:06 PM
	When will you simulate 4-20mA as oppose to sourcing 4-20mA. I notice some of the calibration instruments gives you a choice to use one or the other.
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Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#1 Re: 4-20mA Simulating vs Sourcing 07/28/2011 11:57 PM
	I don't think there is anything "vs" or "opposed" between simulating and sourcing. Do you mean sinking vs sourcing? __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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Turbotroll3 Power-User Join Date: Oct 2008 Location: Houston, Texas Posts: 252 Good Answers: 5	#2 Re: 4-20mA Simulating vs Sourcing 07/29/2011 5:25 PM
	The difference is not as clear cut as one might think. You can simulate a transmitter by sourcing current if the transmitter powers the loop. Typically known as a 4 wire transmitter where power is not supplied to the transmitter through the 4~20 mA output. You can simulate a transmitter by sinking current if the instrument or an external source powers the loop. Typically known as a 2 wire transmitter where power is supplied to the transmitter through the 4~20 mA output. As a general rule: When the 4 to 20 mA loop is powered by the transmitter, use source to drive a signal back to the instrument. When the 4 to 20 mA loop is powered by the instrument, use sink to drive a signal back to the instrument. This seems the best I can do on a sleepy Friday afternoon! Have FUN! TT3 __________________ If the software can detect, compensate, avoid, or correct an anomalous condition in the system, it is, by definition, a software problem-regardless of the root cause. In the long run, for most classes of problems, it is cheaper to fix it in the SW
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