Problems with DAQ

[Quiksilver]

Hi Labview Helpers I have the following problem I hope you can help me with:

I have Labview 8 and a 6025E Series Multi-DAQ

I am trying to sense a current signal by a 4 wrap Hall effect Current probe and it works I can see the signal on

my oscilloscope, however, when I connect it to my DAQ board on AIO 0 the voltage dissapears.  I have differential input configuration.  My configuration is in the picture and program attached.

Is there anything wrong with my approach/syntax.  I am trying to acquire a waveform from the start of my TTL to 2.2ms after the start at 500 Samples over this period.  The amplitude on the oscilloscope goes up to 1.2 volts however you can see that on my front panel I am only reading 2 mV noise. 

I appreciate any input Thanks

[Quiksilver]

Here is the picture of my connections

[AnalogKid2DigitalMan]

Your image shows you are wired to AI1/AI9 yet you mention AI0. Is that a typo?

When you say the volatge dissappears do you mean you no longer see a signal on the scope when the hall device is connected to the DAQ card?

Also for diffential mode you typically do not wire the input to ground (AI9). You may want to read the section in the 6025 manual about selection and wiring of the 3 various analog input configurations. From the looks of your diagram the hall output is ground referenced, not floating.

[TheWoost]

Hi Quiksilver,

I see no problems with the syntax of your LabVIEW code.  For a differential input, you are correct in using AI1 and AI9 for ACH(+) and ACH(-).  However, I'm not clear on whether you have the proper terminal configuration selected for your sensor.  Is the current probe you are using grounded, and if so, is this the same ground that your JPEG indicates that AIGND and AI9 are connected to?  For more information about signal sources please refer to a document on our NI Developer Zone that discusses this here.

Another thing to consider is that you are wanting to acquire 500 samples in a 2.2ms period after your start trigger.  This calculates to a sampling frequency of a little over 227kS/s.  However, the 6025E has a maximum sampling frequency of 200kS/s.  You may want to consider an M-Series data acquisition board that could provide much higher sampling frequency capabilities.

Regards,
Andrew W
National Instruments