Difference between waveform and array

[Water]

Hi,

Not too sure if this is the right place to post this.

Anyway have a question regarding the difference between this two when I try to set the DAQMxread to 1 channel and N-sample. It gave the option of choosing between two types of output (1) an 1D array of double (2) waveform. I have set the acquisition to finite samples and the samples read into memory from buffer would be FFT using the Spectral Measurement express.vi. which one would provide the correct measurement? It seem that the representation of the spectrum with different inputt format(1D array of double or waveform) will give different result or rather different representation

For the 1D array input, the spectral measurement stop at 0.5(i assume this is the half sampling frequency) along the frequency axis while for the waveform, it represent it in the frequency value for the frequency axis.

Need some clarification for this query

Thanks a lot for your help!

[Dennis_Knutson]

The 1D array is just an array of amplitude measurements. A waveform data type is a cluster. In the cluster is the same 1D array, a timestamp (start time of the acquisition), and the dt or the time between samples. When you wire a 1D array to one of the FFT functions, because there is no sample rate information in an array, the FFT assumes a sample rate of. With the waveform data type, since the actual sample rate is part of the data, the FFT will use that and give you an accurate result.