SCXI-1520 bad channel when cabled

[ThaDrewid]

I am getting bad readings on channel 1 whenever I have an SCXI-1520 module in my system cabled to a SCXI-1349 chassis adapter.  Null offset and shunt calibration fails on this channel and the readings either rail to min/max or hover around zero no matter what.  I have tried moving modules around and it is always the cabled module that has problems.  My hardware and software is as follows:

Measurement Studio 7.1

NI-DAQmx 8.0

PCI-6052e

SCXI-1001 Chassis 1
    6x SCXI-1102
    6x SCXI-1520 (SC1Mod6 is cabled with SCXI-1346 and has an SCXI-1180 feedthrough adapter)

SCXI-1001 Chassis 2
    12x SCXI-1520 (SC2Mod1 is cabled with SCXI-1346)

SCXI-1001 Chassis 3
    12x SCXI-1520 (SC3Mod1 is cabled with SCXI-1346)

SCXI-1001 Chassis 4
    2x SCXI-1520 (SC4Mod1 is cabled with SCXI-1349)

What am I doing wrong?

-drew

[Otis]

Drew,

Have you checked for bent pins?  It sounds like there may be a communication problem between the board and the cabled module.

Do all of the other modules in your system behave as you would expect them to?

I look forward to your reply,

[ThaDrewid]

I checked for bent pins, etc. and haven't found any.  All other channels seem to be normal.  It is weird though, I thought the readings on that first channel were bad, but they looked normal after I inspected for bent pins and put everything back together.  The strain calibration still fails with a null offset error saying the coarse pot setting is out of range.

[Otis]

Hi Drew,

Can you try going into MAX and just doing a calibration on one channel?  Does that also fail?  Or does it only fail when you're trying to calibrate multiple channels?

Also, before you calibrate, make sure that your readings on that one channel are what you expect them to be.  I have an idea of what may be going on, but we need to try this one channel at a time first.

Thanks,

[ThaDrewid]

Sorry for taking a bit of time off from this issue but things here have been a little hectic.  After more testing on this problem, I have confirmed that the SCXI-1349 adapter is somehow causing the problem.  I have even swapped my old SCXI-1349 with another unit just to be sure mine was not bad.  The same problem crops up.

Just to recap, I get bad/unexpected readings on the first channel of whatever SCXI-1520 module is attached to the SCXI-1349 adapter on the fourth chassis.  I confirmed this by hooking a decade resistor up to the channel and noting the change in reading vs. resistance change.  I also wrote a shunt cal/null offset calibration program to check my strain channels.  When I run my routine on this bad channel, it fails. It doesn't matter whether I  When I run the MAX calibration, it succeeds somehow.  I tried moving the SCXI-1349 adapter to the third chassis and get similar results not for the first channel but the second channel of the attached SCXI-1520 module.  I then replaced the SCXI-1349 adapter with a SCXI-1346 multi-chassis adapter so that the chassis cable chain ends at the third chassis (i.e. there is no downstream chassis cabled).  This seems to fix the problem.  So is the solution here that I need to go out and buy another SCXI-1346 adapter?  Does this have other ramifications for my system if there is no 'termination' to the interchassis bus?  Why am I seeing these problems with the SCXI-1349?

Thanks in advance for your help.

-drew

[Nicholas_B]

Greetings Drew,

I found two KnowledgeBase articles that seem to describe your issue and provide a solution.

The first, found here, describes the fact that you will need to use the 1346 in your system.  The problem may be stemming from the use of the 1180 feedthrough module. 

The second article, found here, describes how to eliminate the offset nulling "out of range" error. 

Please let me know if you need any additonal help or information...

Regards,

Nicholas B, National Instruments