NI Scope FFT frequency shift

[ninskaya]

Hi,

I use a DAC card (NI PXI/PCI-5401) to generate a sinus and a ADC card (NI-PCI-5911) to pickup this sinus. To transform the time domain sinus signal into a frequency domain signal, I have used an example of NI using the NI-Scope vi "Add process" with FFT.   Somehow, the sinus generated at 50kHz is shown in the frequency domain at a frequency of approximately 58kHz. I don't understand this shift. Would you have an idea? Both vis used are attached

Best,

Ninskaya

[Honsel]

Hi Ninskaya!

What happens if you try higher or lower frequencies?

Best regards,
Hendrik

Message Edited by Honsel on 05-30-2006 08:24 AM

[ninskaya]

Hi Henrik,

Thank you for your help. Actually, I had programmed a sinus with a sample rate, which was lower than the one of the card. After changing this, the shift disappeared. Thanks again.

Ninskaya