Trouble reading 4-20mA into Micrologix 1000

[Electrician4JC 1]

Hello all. I have a problem trying to read 4-20mA into a Micrologix 1000 Analog PLC. Not sure if my issue is with wiring, or an option within the PLC, or even the PLC itself. I scoured the message boards and found a wiring schematic for creating 4-20mA using a potentiometer. One leg of the Pot wired in series to 950ohm resistors. Wiper of the pot wired in to the IA/2(I+). Last leg of the pot wired to the 0VDC bus. IA(I-) wired to the 0VDC bus [see attached picture] When I check my circuit with a meter, I am able to read 4-20mA fine, but when I connect to the PLC and check my inputs with RsLogix (in online mode), I:0.6 just seems to flipflop between 0 and 1, and doesn't seem to change no matter what direction I rotate the pot knob. I've checked the IO Configuration>IO Setup>Input Enables and made sure that Input #2 is turned on. So not quite sure what else I can do to read the signal into the PLC. Any suggestions are appreciated. Thank you and blessings! Mark.

[JRoss 84]

What's your full model number? I was under the impression that the analog inputs built into the MLX base units was 0-10V only.

[HKU_MS 0]

I think J Ross is right on that one I have not used the micrologix 1000 but it is that way on the 1100 I have worked around this as long as you don't need high accuracy you can add a resistance around 450 OHMs across I+ to I- to generate a voltage drop that you can then scale as needed. also the input should be set to read at the highest time rate you can get away with as this system will have some built in noise.

[Mickey 71]

HKU_MS, JRoss FYI, The ML1000's analog inputs can be voltage or current. See picture -10.5 to + 10.5 voltsDC -21 to +21 ma current The ML1100's embedded analog inputs are 0-10 vdc only. See picture. ML1000Analog.pdf ML1100EmbeddedAnalog.pdf

[HKU_MS 0]

paper work trumps blind guessing every time! Electrician4JC's circuit should be giving IA/2 what it needs to read. how are you looking at it in the program Online at the input data file or at an addressed function?

[Electrician4JC 1]

Hello all and thank you for the suggestions and help. Just to answer a previous question, the model number of the Micrologix is a 1761-L20BWA-5A. I finally tracked down the issue to a miswiring. I had connected the pot wiring to a terminal strip, and then brought the signal from the terminal strip to the ML1K. The wiper signal made it to the PLC, but the 0VDC wire somehow was not landed at the terminal strip. Which is why I could read the pot to the terminal strip, but not to the PLC. Anyways, thanks for the suggestions! My bad, but a good learning experience. Thank you all and God bless! Mark.