05-01-2012 10:20 AM
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.
05-01-2012 12:46 PM - edited 05-01-2012 12:46 PM
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
05-01-2012 01:16 PM
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).
05-02-2012 09:25 PM
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?
05-03-2012 07:37 AM
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.