write and read waveform + power spectrum

[Philipp Kravanja]

hi,

i am using the attached vi to calculate a power spectrum of a time domain signal. I would like to save the time domain signal and be able to read it and then use it as input data for the FFT powerspectrum.vi. I used the write and read waveform to and from flie vi´s and saved it as a .txt. It didn´t work. when i opened the .txt there where a lot of weird symbols.
 I also tried to use the export waveform to spreadsheet file.vi but could not read it as an input for the FFT Power spectrum.vi.
 
What would be the best way to solve my problem ?

Thanks for any help

[Philipp Kravanja]

here is the blockdiagramm

[Philipp Kravanja]

by the way, i am using LabVIEW 6.1.
i want to write the time domain signal (=waveform) to a file and the read this file as input for FFT Power spectrum.vi.
actually i want to vary the number of averages and the time window (not the type of window, but the time) to calculate the power spectrum.
Thanks for help

[H. Hager]

Hi Philipp,

It is not advantageous to save the signal in a *.txt - file or in a spreadsheet-file. In current versions of LV it is advisalbe to use the *.tdms-format. But in LV 6.1 this format is not supported. So I think in your case it is the best to use the read/write datalogfile VIs to save your data or read it as input for the FFT power spectrum VI. The disadvantage of this format is, that you are not able to display the data in a text editor programe.

The attachement contains a short, commented application, in which the datalogfile VIs are used. These application is taken out from the NI Example Finder.

To vary the number of averages of the FFT, you only have to vary the numeric value, named "number of averages", in the cluster connected to the "averaging parameters" pin.

Kind regards,

H. Hager