USB-6211 noise problem

[yonijar]

Hi,
I'm using a NI USB-6211 device, on windows XP, and i have problem reading the voltage (attached photo).

My analog differential signal (DC signal from a DC power supply) is connected to analog input in the usb-6211 (to AI1 and AI9 ports).

The signal I'm getting is constantly changing between 0V to the input volt (in the attached picture - 4V) instead of 4V DC.

When i measure other channels, i get voltage jumps between 0-11V, although no voltage exist in other channels.

Also RSE have noise, and the only time the measurment were good was when i connected directly the analog input to the DAQ analog output.

I also use a NI USB-6008 and it works well.

The self test is ok, and i also did self calibration, and of course installed the driver NI-DAQmx 9.8.

i hope someone can help me,

Yoni.

[Eric-E]

Hello Yonijar!

Thanks for the screenshot. It looks like there is a "yellow bang" or exclamation mark inside a yellow symbol next to your device. This is due to an issue between USB 2.0 and Windows XP which causes data to be read incorrectly. Please take a look at the KnowledgeBase link below to find out a bit more information. 

http://ae.natinst.com/public.nsf/webPreview/4BE60A5A38574E59862578D8005CFD4F?OpenDocument

The typical solution is to download the USB hotfix for XP:

http://support.microsoft.com/kb/969238

I hope this helps, but let me know either way.

Thanks,

Eric-E

[yonijar]

Thank you Eric-E, 

I've installed the hotFix and the "yellow bang" is now gone, but the problem remains..

I've also installed "DAQ Diagnostic Utility" and diagnostic results were "pass" for all the tests.

I also tried a different cable and it didn't helped.

any more ideas? 

how can i check if the problem is in the DAQ itself?

thank you for your help.

[Eric-E · Accepted solution]

It might be a good idea to test with a 9 V battery using a differential connection with the wiring configuration outlined in the manual (picture and link below). I know it sounds basic, but re-seating the black I/O connector to the device might help. Make sure you refference AI GND as well.

http://www.ni.com/pdf/manuals/371931f.pdf

[yonijar]

Thank you very much, it did solve the problem.

I believe that the problem is caused because the DC power supply have +,-,& ground terminals -  connecting the minus terminal to ground

also solved the problem.

[Spaulding9717]

I'm trying to reduce the noise that is being read from my pressure transducer with a USB-6211 DAQ, but everything I have tried is leading to an incorrect measurement. In the form I have it now is the closest I'm getting to the correct measurement, but with a lot of noise. Any ideas on how to reduce this noise?

[DollaBrillz]

I have attached a link on our website that goes through several steps for troubleshooting noise for analog signals.

http://www.ni.com/white-paper/3344/en/

I hope this helps!