SMART TRANSMITTER

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vishals Member Join Date: Mar 2008 Posts: 5	SMART TRANSMITTER 05/18/2008 11:54 PM
	what is difference between conventional 4-20ma transmitter and smart transmitter?
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Kilowatt0 Guru Join Date: Aug 2007 Location: Earth - I think. Posts: 2143 Good Answers: 165	#1 Re: SMART TRANSMITTER 05/19/2008 12:54 AM
	The conventional 4-20ma transmitter only sends information about the process variable being measured, by varying the current (4-20ma). A smart transmitter can send/receive information about the instrument itself, e.g. zero and span info, instrument loop identification number, etc. There are basically 2 different ways that information is passed back and forth with a smart transmitter: 1. By varying the 4-20ma signal in a similar fashion to RS232. 2. Use the 4-20ma (essentially DC) as a "carrier" and put a modulated AC signal on top of it. By using a choke and a cap, you can split the 2 signals at both ends. __________________ TANSTAAFL (If you don't know what that means, Google it - yourself)
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Vulcan Guru Join Date: Oct 2006 Location: Northern Mindanao, Philippines Posts: 2147 Good Answers: 53	#2 Re: SMART TRANSMITTER 05/21/2008 9:24 AM
	Kilowatt0 already gave a good answer but I just want to add this: There used to be a time when "smart" merely meant that the instrument had a microprocessor in it. Where the conventional transmitter had two potentiometers to adjust the zero and span, the smart transmitters had buttons (anywhere from two to four) and an lcd display. This enabled the user to change the instrument's characteristics (configuration) and also allowed calibration. Then, the manufacturers developed handhelds that allowed the user to configure and calibrate the instrument with something that looked like a large, overgrown calculator that was not built to be put in your pocket. It's a handheld, right? So hold it in your hand! Nowadays, it's an attachment that you can connect to your laptop and do your configuration or calibration without going to the hot, humid shopfloor. Just be sure that what you're calibrating is the actual instrument that you intended to calibrate. __________________ Miscommunication: when what people heard you say differs from what you said. Make yourself understood.
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Kilowatt0 Guru Join Date: Aug 2007 Location: Earth - I think. Posts: 2143 Good Answers: 165	#3 In reply to #2 Re: SMART TRANSMITTER 05/21/2008 8:59 PM
	. __________________ TANSTAAFL (If you don't know what that means, Google it - yourself)
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