Loss of Coms

Hi all

We having a problem with a Thermo coupler input card, on a SLC500 PLC.
Keep lossing coms with the signals.. Have checked everything that I can think of....
The plant may operate for several weeks without problems and then shuts down.

Once the PLC is reset, everything operates well for a while or several weeks.. any ideas ???

Thanks

Assuming this card is a 1746-nt4 or nt8.
What exactly happens. Do the lights for each channel go out or do they blink?
If you can go on-line with the processor look at the configuration files (the input Files) for the slot that the card is in . That will set up all of the parameters for each channel. The manual is on AB's site.

My guess is that a certain sequence of events writes over what should be there. When that happens you will lose the readings from the card.

When you reset the proc. There is probably an instruction that sets all of those parameters . So The card is fine again for a little while.


Drewcrew6

Loss of communications?

Are you actually getting a loss of communication?

It sounds more like you have a Block Transfer Read instruction that stopped functioning.
By resetting the PLC you re-initiate the BTR and the problem clears up until next time.

Monitor that particular BTR and see if it is the culprit.
You may need to use a timer to re-initiate the BTR, when it fails, until you can find the real problem.

Let us know.
Roger

Sorry I have not had time to go to site personally and see exactly what is actually going on...... As soon as I have any more details I will post another message...

sorry

Paul