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Strange analog behavior on USB-6356

I have a USB-6356 DAQ that I am using an a Windows XP machine running LabVIEW 2011.  The analog side of the DAQ is not behaving as expected.  Using the test panels in MAX, the AI channels show either ~0V or 10.2 V.  For a simple input signal I am measuring a DC voltage generated by a battery through a voltage divider.  I have the signal connected as suggested in the user manual for a floating source: AI+ to V+, AI- to GND and AIGnd to GND.  I tried multiple channels and get the same result.

 

On the analog output channels I get 0.85 Vdc output no matter what I set the output voltage to be or if I set the AO to be a sine wave (signals measured using a digitial multimeter and o-scope). 

 

The digital port appears to be working correctly. I can toggle the state from low to high and the readings are correct.

 

I have applied the DAQ Hotfix patch and this did not change the behavior.

 

The board is relatively new and worked previously so I am not sure what has changed or if I am overlooking something obvious. 

 

Thanks.

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Corey,

 

Unless you omitted it from your description, it sounds like you're missing a connection from V- to AI-.

 

So you'd have V+ to AI+ (Pin 68)

V- to AI- (Pin 34)

and AI- to AIGnd (Pin 34 to Pin 67)

 

Does this line up with what you've done?

 

Dan

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I am using the USB version of the 6356 DAQ so the pin numbers don't match your list, but I am wiring in my signal as you describe.  For example to do analog input on the AI0 channel I am connecting V+ to pin 1 (AI0+), my battery ground to pin 2 (AI0-), and then jumpering pins 2 and 3 (AI0- to AI GND). 

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Hi Corey687,

 

It sounds like you have everything wired properly.  You may want to try to wire your application to another channel such as AI1.  Have you verified with a voltmeter the values you should be seeing?    

Cole R.
National Instruments
Software Engineer
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I verified that I had a DC voltage in the right range using a DMM and tried a couple different AI channels and got the same result.  I ended up contacting NI tech support yesterday afternoon and just sent the board back for inspection there.  If they find a definitive cause for the improper readings I will post that here.

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