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4-20mA simulation circuit for PLC

Hi,

I am looking for a simple circuit to simulate sensor inputs to PLC. Sensors take 12VDC and outputs 4-20mA. I was looking at your XTR series devices which seems to be able to achieve this but I am not sure which one will be ok to use for 12VDC voltage. Also, it would be good to have the range of output from 0 to 24mA rather than 4-20mA so that we can test the PLC input for error inputs as well.

I am electrical engineer with very minimal electronics knowledge so was wondering if someone could help.

I have attached a simple representation of my circuit.



  • There is a product folder for 4-20mA transmitters and receivers at

    http://focus.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&familyId=508&uiTemplateId=NODE_STRY_PGE_T

    In particular, the XTR117 could be of interest for you, it includes its own linear regulator, and the input current could be generated using the Regulated 5V output in series with a potentiomenter to control the current output value.

  • In reply to Avi Chami1:

    Hello,

    Thanks for the help Albert!  You're correct that the XTR117 is likely the best candidate for this type of simple circuit to simulate a 2-wire current loop transmitter. 

    I would suggest a circuit such as the one shown in Figure 1 in the datasheet that I've pasted below. 

    Best Regards,
    Collin Wells
    Precision Linear Applications

    Regards,
    Collin Wells
    General Purpose Amplifier Applications

  • In reply to Collin Wells:

    Hi Collin,

     

    I have seen couple of answers given previously with circuit diagram and components to suit the requirement. Is it possible to get a schematic and calculations? If not I have a circuit calculation for XTR116 which was previously posted so I can work with it. I found a  XTR116 in lab at my work but XTR117 is not available so I will have to buy it. For my application, if I use XTR116 rather than XTR117 then do I miss out on anything? do I need to keep anything else in mind when using XTR116 instead of your suggested XTR117? I have attached files that I found from one of the other questions on ti.com

    1374.XTR116 R-to-I_calculations.zip

  • In reply to harshal patwardhan:

    Hello,

    The XTR116 actually has more features than the XTR117, not less.  The XTR116 includes everything that the XTR117 includes with the addition of a more precise reference voltage of 4.096V. The XTR115 is a similar product with a 2.5V precision reference. 

    Both the XTR117 and XTR116 are fairly easy products to use and full applications diagrams are included in the datasheet.  Figure 1 describes a standard application with a 4-20mA output from a 0.8V to 4V input voltage.  Figure 2 shows how to configure the output for 4-20mA with a 0V minimum input by adding an offset current through the voltage reference.

    Another option to help you understand this circuit better is to download TINA-TI, Texas Instrument's free SPICE simulator at the following link:

    http://www.ti.com/tool/tina-ti

    I have attached a basic SPICE model for the XTR117 that provides a good representation of the basic functional behavior.  When you open the file it is configured for a 4-20mA output with a 0-5V input. 

    0876.XTR117.TSC

    Regards,
    Collin Wells
    Precision Linear Applications 

    Regards,
    Collin Wells
    General Purpose Amplifier Applications