4 channels of 4-20 mA xtr117.

juan camarasa

Other Parts Discussed in Thread: XTR117

i wanna use the xtr117 due to the application requirements(see image). My question is,If those 4 XTR117 are connected to the PLC, the current levels will affect the common gnd?

over 9 years ago

0 Collin Wells over 9 years ago

TI__Guru 62035 points

Hello,

When all four sensors are returning their full-scale values you will have 80mA flowing through the common return. This shouldn't cause issues as long as you've made good Kelvin connections across your current shunt resistors and have a solid GND plane for the current to return through.

Please attach your circuit schematic and PCB layout if you'd like us to review it.

0 juan camarasa over 9 years ago in reply to Collin Wells

Intellectual 390 points

hi Collin

Let me rephrase the question, will the current consumption of this 4 XTR117 affect the gnd level of the system (due to the common ground present in the PLC)?

0 Collin Wells over 9 years ago in reply to juan camarasa

TI__Guru 62035 points

Hi Juan,

We're not experts on building PLC end equipment so if there's something in particular you're concerned with please elaborate a little for us so we can understand your concern.

I believe your concerns are simply about the return currents disturbing other analog circuitry in your design. If that's the case, this concern is present in almost every precision analog design and you must make proper connections such that you don't accidentally create additional differential signals in your signal-chain design. I authored a short blog on this subject which you can find here:

http://e2e.ti.com/blogs_/b/precisionhub/archive/2014/07/04/plant-analog-when-gnd-isn-t-gnd-single-ended-circuits-become-differential.aspx

Basically don't take the "GND" symbol for granted and make sure that you're treating the amplifier circuits as differential circuits like they really are.

0 Van-Ngoc Nong over 9 years ago in reply to Collin Wells

Prodigy 140 points

Hello Collin,

3124.diagram.pdf i have similar design like Juan. In my case i have two XTR117. I also attached the diagram.

My question is if i leave one current loop signal floating, will his current flow through the other current loop signal?

In other words when you see my diagram. If i leave the I_Loop_2 floating and measure the current I_Loop_1, i will

have the current of I_Loop_1 + I_Loop_2.

Regards

Ngoc3513.diagram.pdf

0 Van-Ngoc Nong over 9 years ago in reply to Van-Ngoc Nong

Prodigy 140 points

Sorry,

forget my question. I made a mistake in soldering my breadboard. It works fine now.

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4 channels of 4-20 mA xtr117.