HI Annika,
The XTR116 is a 2-wire current transmitter, where the IRET pin is the local ground of the current transmitter, and this pin needs to float with respect to the Loop Ground.
In other words, the IRET pin can't be connected to the Loop GND or the transmitter can't regulate current. In the schematic above, the IRET and the load resistor is connected to the same GND.
Figure 2, shows the 2-wire current transmitter properly connected, where the 2-wire current transmitter GND (IRET) is allowed to float with respect to the Loop GND:
Please review the short article below, it explains in detail how the 2-wire current transmitter works:
2-Wire 4-20 mA Sensor Transmitters: Understanding the 2-wire Transmitter GND (Part 2)
If you require a current transmitter that uses the same ground as the loop ground, you could consider a 3-wire current transmitter, for example, the XTR111 is a 3-wire current transmitter that can be referred to the same ground as the Loop GND.
If you which to learn more about 2-wire and 3-wire current transmitters, please review the resources below:
Thank you and Best Regards,
Luis Chioye
