xtr117 is not working, power supply is 12VDC serial with a 510 ohm resisitor, but Vreg is 1.2 V respect to Iret.

Hi Bin,

This sounds like a compliance voltage issue where the supply voltage is not high enough to support the load resistor and output current. We wrote a blog about this subject which you can read here: e2e.ti.com/.../two-wire-4-20-ma-transmitters-background-and-common-issues

Try reducing the load resistor to 0 or 10Ohms or increase the supply current to >20V and see if the output current reacts as expected.

Hi Bin,

Try using the attached SPICE simulation file to debug and understand your system better.  The model uses some ideal components so it should be used to check basic understanding and operating functions of the XTR117 product.  If you notice very large voltages or currents, then it's likely something is not connected properly.

I suggest you double-check all of your circuit connections because the circuit should provide basic functionality as you've drawn it. This is shown in the SPICE simulations below:

XTR117_Potentiometer.TSC