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XTR115: Trouble making XTR115 current trasmitter provide proper output current

Scott Daniels
Prodigy 80 points
Part Number: XTR115
Other Parts Discussed in Thread: XTR300, XTR200

Tool/software:

I have this circuit using an XTR115 and using R2 to test the current output. As you can see from the text in the schematic, the output current is only 58 microamps instead of 24mA. I am pretty much at my wits' end here. Do you see anything wrong with the circuit as shown? Or the testing of it? I figure I am missing something obvious but cannot see what.

Also, after watching the TI video Introduction to 4-20-mA current loop transmitters, I realize that I should possibly be using a 3-wire solution (I am providing output current from a PLC). However, neither the video nor the data sheet for the xtr300 make a lot of sense to me in how it is connected to an output device - e.g. the transmitter ground and device ground are shown as different (not connected?). Also, is there a reason the XTR115 chip cannot be used as I am attempting in this application (I am supplying VCC)?

The world of current transmitters is new to me, and I would like as simple of a solution as possible for my application.

Thanks for any help.

  • 0
    TI__Genius 15130 points

    Hi Scott, 

    Happy to help find a solution for you!

    First, I recommend taking a look at the E2E FAQ and article linked here to help understand the different transmitter options available. A main advantage of the 2-wire transmitter like the XTR115 is that the sensor is powered by the transmitter but you need to take caution in connecting IRET correctly as the sensor ground cannot be connected to the supply ground. 3-wire transmitters do not have this limitation but require a local supply.

    The basics of 4-20mA current loop transmitters - Planet Analog

    [FAQ] How do I choose a 4-20mA transmitter? - Amplifiers forum - Amplifiers - TI E2E support forums 

    Based on your requirements mentioned, it does sound like you are needing a 3-wire transmitter solution if you have access to a local supply. This is my assumption since I'm not sure what is connected to J1? 

    I recommend our newest 3-wire XTR, XTR200, as it is a simple current transmitter solution with an integrated output transistor.

    Please let me know which design path you would like to move forward with (either the 2-wire or 3-wire) and I can help with further questions for either solution.

    Thank you!
    Regards,
    Ashley 

  • 0 in reply to Ashley Kang
    Prodigy 80 points

    Thank you. The references were very helpful. That solved my testing problem.

    I really like the XTR200, but it is not currently in production. When do you expect it to be placed into production? What alternative do you recommend in the meantime?