DAQmx - PCI 6071E sample rate problem

[mitulatbati]

Hi all,

I have a PXI-6071E DAQ card, which can acquire at max 1,25MS/s.

I create a task with 4 channels, at sample rate 50 kS/s each. The result waveforms look different, if I do the same at 1kS/s.

The only thing what I chane is the sample rate.

Does anybody know about this kind of strange behavior?

regards

MB

[Dennis_Knutson]

'Different' is not much of a description. How different? Can you post some images that show the difference. Displaying some differences due to sample rate is not strange at all depending on the frequency of the signal that you are measuring. Are you familiar with Nyquist and sampling theory?

[Hillman]

Hi

I was going to post a few hours ago, but got a bit busy.

But Dennis is completly right - what sort of input are you acquiring and is the 50K or the 1K correct.

Regards,

[mitulatbati]

Hi Knight 🙂

Sorry, I have given insufficient input. To answer the second Q first, yes I am familiar with Nyquist and sampling theorem.

I have made two screenshots. Both have been taken on the same software, the only difference is the sample rate. At 1kS/s look all the 4 signals perfect. The same waveform I expect at 40kS/s, just a bit higher resolution.

Just for info:

Dev2/ai3 and Dev2/ai0 are voltages on a resistor, so the difference shoud be the current.

Dev2/ai55 and Dev2/ai57 are motor control signals, the "jungle" at the end is a PWM signal.

So, why look these curves different on different sample rates?

regards

MB