Using two XTR116

Yassine Hayou

Other Parts Discussed in Thread: XTR116

Hello

Can you please tell me if the schematic below is correct or not, because i have the same output signal in both transmitters, if it's not correct what should i do ?

Thank you

over 7 years ago

0 Collin Wells over 7 years ago

TI__Guru 62085 points

Hi Yassine,

This system will have issues if the two "GND" nets that connect to pin 3 of the two XTR116 devices are connected together. This is because the IRET pin of the XTR devices must be allowed to float up and down as the output current changes. This is explained in the first blog post I've linked at the bottom of this message. If you're trying to control the output of two 2-wire transmitters with one MCU or multi-channel DAC, then you'll have to isolate the two transmitters from each other with a digital isolator. Information about isolating the transmitter input is described in the 2-4th blogs below.

2-Wire 4-20mA – IRET Can’t connect to Vloop GND
https://e2e.ti.com/blogs_/b/precisionhub/archive/2014/12/09/part-2-two-wire-4-20-ma-transmitters-background-and-common-issues

2-Wire 4-20mA – IRET < 4mA
https://e2e.ti.com/blogs_/b/precisionhub/archive/2015/01/13/two-wire-4-20ma-transmitters-background-and-common-issues-part-3

2-Wire 4-20mA – Controlling 2-Wire Transmitters with Externally Powered Sources
https://e2e.ti.com/blogs_/b/precisionhub/archive/2015/02/24/two-wire-4-20ma-transmitters-background-and-common-issues-part-4

2-Wire 4-20mA – Input Isolated Sensor Transmitter
https://e2e.ti.com/blogs_/b/precisionhub/archive/2015/03/10/2-wire-4-20ma-sensor-transmitters-background-and-common-issues-part-5