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DAQ hardware damaged?

Hi all, I have just assembled a new DAQ system to measure temperature. The DAQ components that I use are PCI 6251 with SCXI 1102 and TBX 1303 terminal. Immediately after the setup, I checked the system with a fluke temperature calibrator. It works fine and accurately with an error of within 1 degree F. However, when I add in a SCXI 1161 card and checked the temp measurement again, it suddenly mulfunction. I started to measure 'Ghost' signal; signal that gives the max value  of whichever range that I give. I tried removing the SCXI 1161 card and reassemble all hardware again but it does not work anymore. What could have happened by adding another SCXI 1161 card to it? Does anybody has such experiences that could advise and share with me? I would greatly appreciate it.  Thanks..
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Hello Phooi,

I'm not exactly sure what could be causing the behavior you are seeing, but the first place to start would be to verify that your system is installed and configured correctly.  When working with both analog and digital SCXI modules, you must use the analog module as the communicating module because it can transfer both analog and digital signals from the SCXI bus to the DAQ device.  I am assuming you are connecting the SCXI system to your NI PCI 6251 with a 68-pin cable connected through an SCXI 1349 adapter into the back of one of your modules.  Make sure that the module that you are connecting to is your SCXI 1102 and not the SCXI 1161.

The next thing I would try is to re-configure your system in Measurement & Automation Explorer (MAX).  Anytime you make a change to the hardware in your SCXI system, you need to rescan for devices in MAX to reconfigure your changed system.  Here are the basic steps for configuring your SCXI system:

1.  Under 'My System', expand 'Devices and Interfaces'.
2.  Right-click 'NI-DAQmx Devices' and select Create New >> NI-DAQmx SCXI Chassis and select your chassis.
3.  Under the 'Modules' tab, autodetect your modules and select the accessories associated with each module.
4.  Under the 'Chassis' tab, select your NI PCI-6251 as the 'Chassis Communicator' and select your SCXI 1102 as the 'Communicating SCXI Module Slot'.
5.  Click 'OK' to save your changes.

You must re-autodetect your modules and re-configure your chassis communication settings every time you make a change to the hardware in your system.

My final thought is that you might have blown a fuse in your SCXI chassis.  There are two sets of fuses in the chassis: one associated with the main power for the chassis, and another protecting the analog circuitry in the backplane of the chassis.  If the first fuse is blown, you will not be able to even power on your chassis.  If the second set of fuses (protecting the analog circuitry) are blown, you will still be able to power on and autodetect your modules, but you will not be able to acquire any analog input data.  SCXI modules are NOT hot-swappable, i.e. you need to power down the chassis before plugging in or removing modules from your system.  Swapping SCXI modules with the chassis powered on could have resulted in a blown fuse and the behavior you are seeing.  A blown fuse is not that serious and can be replaced by you without having to send the chassis back to NI for repairs.  Here is a link to a knowledgebase describing how to diagnose and fix blown fuses in a system.

KnowledgeBase 29EHH5SV: SCXI Fuse Information

In conclusion, try starting from scratch and fully reconfiguring your SCXI system in MAX.  If that does not work, investigate the status of the fuses in your chassis for signs that they might be blown.  If none of these suggestions solves your problem, post another reply to this thread with your progress and hopefully we can get you up and running.

Regards,
Travis Gorkin
Applications Engineering
National Instruments
www.ni.com/support
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Travis, thanks a lot for the very good advises. I went through the step accordinngly per what you said and yes, I found the problem. I found the 1.5 A fuse behind the fan of the chassis blown.

I have it changed out and it's back on business again.

This is the first time I use this thread and I must say it is effective. Smiley Happy 

Phooi
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