SLC Analog Input Card Issue

[G_DeMark 2]

I am having an issue with a 1746-NI8 analog input card installed in slot 3 of an SLC 500 1747-L541.  Apparently the PLC is not seeing the card.  The card has been replaced one time already.  I am wondering if there is an issue with the backplane?  I do have an open slot available in position 4.  I may try and install the card in that slot next.   One very important note is that after replacing the input card the machine worked for several hours without any errors.  Only after the machine was powered down briefly and then powered back up did the card show the error.

If anyone has suggestions that would be super.

Thanks

Edited 9 May 2017 by G_DeMark

[kaiser_will 65]

The 1746-NI8 analog input module is faulting after power cycle.  This analog module goes through Power-Up Diagnostics.  When the module is faulted, go online with the program and take note of the input module's Input word, bits 12-15 (page 5-14).  You are disabling the unused channels?   You have verified the input channel configurations?   http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1746-um020_-en-p.pdf

[G_DeMark 2]

At the moment the machine is working fine again.  I think there is some requirement that the processor should be in program mode when the new analog module is installed so that when it powers up the module is initialized.  I am not sure about this, can anyone comment on the specific requirement.

-  All channels are enabled (however, I do not believe they are all being used)  I am trying to find a reliable electrical print from the people that work at this plant.  I am assuming is a best practice to disable unused channels?

- Ch 1 and Ch 6 do have an under range errors.  But I think that goes away when the machine is cycling and reading real data.

Thanks

[G_DeMark 2]

I have been down at the plant all day and I can not re-create the issue.  I have  cycled power on the machine a half dozen times and no issues were found.  Very strange.

[kaiser_will 65]

There is a note in the ControlLogix analog input modules user manual, page 53, that specifies disabling unused analog channels so extraneous alarm bits are not set.  http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1756-um009_-en-p.pdf

PLC-5 4-channel analog input modules specified unused channels have their signal + & - terminals tied to common to "reduce noise" (pg 2-12).  This practice eliminates unused channels having their data value bobble around possibly creating confusion for technicians.  http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1771-um663_-en-p.pdf