AI acquire waveform. maximum readable data

[Ronald]

Hello,

For acquiring data from an DC-accelerometer I'm using the 'AI acquire
waveform.VI' to perform this task. I'm scanning for 10 seconds at a sampling
rate of 10.000 S/s. When I'm looking at the amplitude spectrum I find
spectral components below 1 Hz which can't physically be there. (10 seconds,
so df = 0.1 Hz). Is it possible that this has got to do with the acquiring
technique??

Thanx,

Ron@ld

[martin_00]

Are you using a lowpass-filter for
signalconditioning???
The low frequency components could come
from alaising effects..
(see the NI DAQ tutorial)

[Raecine Meza]

To expand on the previos response, Nyquist Thereom tells us we need to sample at least twice as fast as the signal's frequency to get an accurate sampling and reduce aliasing effects. Aliasing can also be due to noise sources in the environment so using a low-pass filter is still a good idea. Here is a Knowledge Base on aliasing and low-pass filtering:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/68f14e8e26b3d101862569350069e0b9?OpenDocument