Russ
Lifetime Supporting Member
We switched from a SLC5/04 to a 5069-L320ER, and the SLC's NI4's were replaced with the 5069-IY4, which is a pretty neat card; however, the IY4's don't use isolated channels... which lead to an issue...
One of the 4-20mA loops passes through a chart recorder. When we wired them like the original NI4, this channel showed an OOR value, which is somewhere around 3mA. In troubleshooting it we shorted the neg-comm and it worked.. however, when this occurred the other inputs went out of scale.
We tried shorting all negs-comms, and it didn't change anything. The one going through the chart recorder worked fine, but the
rest were garbage. We found that we could leave the other channel's neg-comm shorts in place and remove the one channel neg-comm short, and the other channels worked fine.
I spoke with Rockwell Tech Support, and it seems clear that the channel passing through the chart recorder is creating an uncommon ground, and it sounds like the only viable options are to either loop the channel into the card (like the others) and send a 4-20mA to the chart recorder, or add another IY4, and drop that oddball signal there.
While both are possible, it seems like there should be a way to get what we have to work. I'd like to check the ground from the chart recorder, and possibly redoing it (the equipment is 25 years old). but I'm not sure if that would be a viable approach, or a waste of time.
Has anyone run into something similar? How did you resolve it?
One of the 4-20mA loops passes through a chart recorder. When we wired them like the original NI4, this channel showed an OOR value, which is somewhere around 3mA. In troubleshooting it we shorted the neg-comm and it worked.. however, when this occurred the other inputs went out of scale.
We tried shorting all negs-comms, and it didn't change anything. The one going through the chart recorder worked fine, but the
rest were garbage. We found that we could leave the other channel's neg-comm shorts in place and remove the one channel neg-comm short, and the other channels worked fine.
I spoke with Rockwell Tech Support, and it seems clear that the channel passing through the chart recorder is creating an uncommon ground, and it sounds like the only viable options are to either loop the channel into the card (like the others) and send a 4-20mA to the chart recorder, or add another IY4, and drop that oddball signal there.
While both are possible, it seems like there should be a way to get what we have to work. I'd like to check the ground from the chart recorder, and possibly redoing it (the equipment is 25 years old). but I'm not sure if that would be a viable approach, or a waste of time.
Has anyone run into something similar? How did you resolve it?