Gluggavedur
Member
Hello. PLC beginner here, so apologies in advance for any incorrect terminology or poor communication.
I have an SLC 500 Thermocouple/mV Analog Input Module 1746-NT8 on one of our PLCs. It is reading no input on channels 0, 1, and 7. This seems to be an issue with the Module directly; I removed the terminal block and swapped the module with another 1746-NT8 that we had on hand, and that fixed the problem on the first PLC. However, the issue followed the module to another PLC. Again, the wiring all checks out on the terminal block (and, in fact, when the terminal block is used on the functioning module in this second PLC, all the channels work). But when using the offending module, channels 0, 1, and 7 do not show readings.
Since the problem doesn’t follow the terminal blocks, and isn’t tied to the backplane or the PLC. I don’t think it’s related to the cold junction compensation, right? I don’t see any visible damage on the module or module circuit board. I can’t find anything that would connect channels 0, 1, and 7.
Thoughts? Thanks in advance!
Background: We have a Rockwell automation system and Allen-Bradley equipment. One of our PLCs was without power for an extended time and ended up losing its programming. While it was not powered (but still grounded, so electrically connected) there was also a lightning-related event at our facility, and several of our pieces of equipment were impacted by that. This issue showed up on the module that was connected to that PLC at the time. We know the components were working the last time that equipment was used (roughly a year ago?).
I have an SLC 500 Thermocouple/mV Analog Input Module 1746-NT8 on one of our PLCs. It is reading no input on channels 0, 1, and 7. This seems to be an issue with the Module directly; I removed the terminal block and swapped the module with another 1746-NT8 that we had on hand, and that fixed the problem on the first PLC. However, the issue followed the module to another PLC. Again, the wiring all checks out on the terminal block (and, in fact, when the terminal block is used on the functioning module in this second PLC, all the channels work). But when using the offending module, channels 0, 1, and 7 do not show readings.
Since the problem doesn’t follow the terminal blocks, and isn’t tied to the backplane or the PLC. I don’t think it’s related to the cold junction compensation, right? I don’t see any visible damage on the module or module circuit board. I can’t find anything that would connect channels 0, 1, and 7.
Thoughts? Thanks in advance!
Background: We have a Rockwell automation system and Allen-Bradley equipment. One of our PLCs was without power for an extended time and ended up losing its programming. While it was not powered (but still grounded, so electrically connected) there was also a lightning-related event at our facility, and several of our pieces of equipment were impacted by that. This issue showed up on the module that was connected to that PLC at the time. We know the components were working the last time that equipment was used (roughly a year ago?).
