DAQmx problem for acquisition

[mahasan]

Hi,

I am using the NI product ADC (NI 9215 with BNC, High speed USB carrier Ni USB 9162) for acquisition of analog signal using LabView and after that the signals are written into a text file.

At the moment.I have generated the signal using function generator and passing through the ADC using LabView.

The problem is, after acquiring the signal through ADC, the amplitude of the signal (that is acquired through ADC) is getting very much much higher!!!!

Could you please advise me how to solve this problem????

Thanks!!!!!!!

Hasan

[Pete.Dunc]

Hi mahasan

Thanks for using the forums!  I have a couple of questions to help us start working towards a solution;

• Are you connecting the function generator directly to the 9215 BNC-BNC?
• What function are you generating?

It will be useful to know what you are expecting to read as compared to what you are actually reading.

Hope to hear from you soon.

[mahasan]

Hi Peter,

Thanks!!!!

Yes..I am connecting the function generator directly to the 9215 BNC-BNC..

And, secondly I am using Sine wave from function generator....

Could you please advise me?

Thanks..

Regards,

--

mhasan

[Beutlich]

Are you specifying the value as RMS and reading the value as peak-peak?

[mahasan]

Hi,

Thank you so much.

Actually, I did not specifying RMS.

I have generated the Sine wavefrom (signal) by function generator and confirmed through the Oscilloscope.

Then, I have used the LabView to write that signal into the file through ADC but, the magnitude becomes much much higher in the LabView waveform graph (Attached )

Thank you again for helping

--

[AnalogKid2DigitalMan]

In your loop, the DAQmxRead data type is set to Raw 16 bit integer. Click on that pull down box and try selecting Analog/SingleChannel/MultipleSamples.

Some of your other wires may break due to the change of data type, you may have to adjust some functions as needed.

-AK2DM

[mahasan]

Hi,

Thank you so much for your reply and advice.

I have changed accordingly but still not able to solve the problem.

Forexample, I have checked the sine wave that is generated from function generator by using Oscilloscope and measure the voltage..e.g : peak-peak voltage 6V.

but, when I am using the LabView design for acquisition then the voltage of peak-peak is not really follow what was in Oscilloscope..

I have attached here my design for your kind references..

Could you please advice me?

Thank you again.

[AnalogKid2DigitalMan]

Can you attach an image of your front panel showing the sine wave captured in the graph and also an image of what the oscilloscope displays?

-AK2DM

[mahasan]

Hi,

Thank you for your kind concern.

I have attached here (3 Images) :

                                 1. Frontal panel image

                                 2. Oscilloscope Image

                                 3. Data that is acquired through LabView  (txt file) 

I hope it may be helpful for us to solve the problem.

Looking forward to hear from you.

Thank you again.

[AnalogKid2DigitalMan]

Interesting, the DAQ voltage is biased negative, and much lower amplitude indeed.

What two pins of your DAQ card have you connected the signal generator to?

Have you tried another analog input channel?

-AK2DM