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How to read the signal from a 4-20 mA HART device with LabVIEW?

Hi everybody, I'm trying to collect the data from a HART pressure transmiter (Rosemount 3051S) with LabVIEW, I tried to put a 250 ohm resistor in the loop to convert the 4-20 mA output to 1-5 VDC output, so I can capture it with our current I/O DAQ, but the signal is fluctuating pretty bad, and the error is way too high to be used. Since the transmiter is kinda different, the power input pins are also used for signal output, I wonder if it is possible to just get a current input DAQ from NI and capture the signal directly?


I'm also not sure about the HART protocol, seems like if I don't put a resistor in the loop, the HART protocol won't work, so does that mean that is the only way I can use the 4-20 analog signal? or if I put a 250 ohm resistor in the loop, is it possible to get the digital signal with LabVIEW and how?


I hope you guys can give me a better idea, any suggestions will be appreciated.


Thanks for viewing!



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Duplicate Post.


Please don't post the same question multiple times.

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although 7 years have passed since this post still NI does not have a solution for HART communication, or how to extract a 4-20mA signal from HART. I am one of those who bought equipment over 20K euro for 5 projects that do not work properly just because of this. All sensors are for design only, NI equipments are not able to interpret their signals. I'm still looking for solutions to this problem at a reasonable cost, hoping to recover the investment started four years ago.

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Where are you trying to read the 4-20mA signal from?  If you are tying to use the PWR/COMM terminals you will need a HART converter to convert the HART protocol to something else like Modbus or something else. 


You do not mention if you have a transmitter that has a dedicated mA output that would have to be configured with a field communicator.


You would need to add specific information about each piece of equipment and specifically where you are reading the output that you are having trouble with.


Have you tried searching Google for "Hart converter" ?


Have you taken a look at this?


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