Logic for 1771-NIV/A

[jwardla]

I am trying to set up a 4-20 input (conv to 1-5vdc) when I look at the data it displays a -5494. What am I doing wrong. I used the insert logic feature. Calibration maybe?

 

[Mark Buskell]

4-20 input

Please forgive me if you have already tried this. Have you tried swapping your + and - wires and see what your input does then.

If you have, let me know and then I will look at some old logic that I have to see if I can find something that might need to be changed in the parameters.

 

[Mark Buskell]

Are you set to Two's Compliment Binary?

 

[akreel]

I'm not familiar with that module, so I'm talking out of my backside on this one, but:

1. Are there configuration jumpers on the module?
2. Are there configuration bits in the I/O table of your program? The analog module for the SLC platform (1746-NI4???) needs to be configured by setting I/O bits.
3. Is the module TRULY 4-20ma or does it read a slightly wider range? I had a scaling issue once because the module was really scaled 0-21ma.

Even if you've missed one of these, I can't really imagine why you'd be seeing a negative value (unless your transmitter isn't transmitting, or the module isn't receiving). But, sometimes strange things DO happen.

If all else fails... jiggle the handle.

AK

 

[g.robert]

Are you sure you are getting the analog input from the field device?

I would verify this with a meter or use a simulator to input known 4-20ma signal (or 1-5vdc). This will let you know if problem is in program or source.

 

[kamenges]

I think Mark's first comment has some validity.
In my experience the 1771-NIV comes configured out of the box +/-32767 for a bipolar full scale input. If you don't explicitly change this with the appropriate field set to a non-zero value in the configuration BTR that is what you get. I also know that the 4-20mA input is not a power sourcing style input. If the 4-20mA transmitter you are dealing with is a 2-wire as opposed to a 4-wire device, you need to provide a supply from something other than the input module. So the 4-20mA input is polarity sensitive. The direction of current flow through the module will determine the sign of the input.

Keith