Intermittent SCXI module shows step change in data

[DieselPower]

I have an SCXI-1001 with nine modules in it.  The first four modules are reading voltage and the last five read temperature using thermocouples.  I am not using the 3rd, nor the 8th or 9th modules.  Intermittently, and seemingly more in the middle of the night, the thermocouples from the 7th module will show a step change in response that is not real.  Each channel will have a drastic offset change.  These are the things we've tried to change:

5th-7th SCXI 1125s swapped out.

7th SCXI 1328 swapped out.

PCI-MIO 16XE swapped out.

Cable from MIO to SCXI swapped.

SCXI Chassis swapped.

Cable connector to module 1 tried on module 1 or 2 and also swapped.

Yet the problem persists.  I've updated the drivers and I'm using the same program that I use in many other cells and I have never seen this problem before.  What could be causing this issue?

Thanks.

[CWolf]

Michael,

Sounds like you have been very thorough in your troubleshooting of this issue.   When you made all these changes, did the issue follow the SCXI module, or the slot, or was it random?  Also, could you post a screenshot of the errant readings you are receiving? 

When you start getting the incorrect data, does it eventually go away, or do you have to restart the system to get good data again?

Thanks for the information,

-Christina

[DieselPower]

I never tried the suspect SCXI 1125 from slot 7 in any other slot.  The problem only happened on slot 7.  I hooked the thermocouples from slot 7 up to slot 8 this weekend (different, but pre-existing wiring) and they had no problems. The blue channel on the attached data set is on slot 6.  The red, green, and purple channels are on slot 7.  You can see that they all undergo an instantanous step change in output while module the module 6 channel stays the same.  It seems as though channels are getting confused with each other (positive of one channel minus the negative of another channel) because green changes to the same trend as red was, but with a different offset.  Once the problem starts, it does not stop.

Message Edited by SCXI and MS 2k3-VB.NET on 11-23-2009 11:11 AM

[CWolf]

Michael,

If I understand you correctly, any module you put in slot 7 seems to show this behavior, even though those same modules work in other slots.   Does your DAQ card pass the self test in MAX?  Also, do all the channels seem to work fine if the SCXI chassis is not plugged in?  Do you have any other types of DAQ cards that you could try in the system?  (Perhaps an M series or USB DAQ card?)  When you change the DAQ card for a different one, do you still get this behavior in slot 7?  What about when you switch out the chassis?  

-Christina

[DieselPower]

The DAQ card does pass the self test.

How can I know if the channels work find if I don't plug the chassis in?

I have tried two different MIO boards, and this is the same configuration that we use all over the place.

I have tried two different chassis with the same results.