回复： Saving FFT PSD waveform to TDMS file maintaining x-axis scale

[Donners]

Hi all,

I'm having trouble saving a Power Spectral Density waveform to a TDMS file because the method I'm using is losing the x-axis (frequency) scaling. The only way I can get it to save is extracting the magnitude from the waveform and saving that in the TDMS file. This loses all the frequency information.

Does anyone know how I can save the PSD information in a TDMS file or failing that, any type of file?

Thank you,

[deppSu]

Hi,

I've downloaded and took a look at the "Data Calculations TDMS 4.vi", however I'm not sure which part in the VI you have problem with. Would you please offer more informatin?

[Donners]

Hi deppSu,

If you look at the jpeg of the front panel, the frequency of the 'Power Spectral Density 2' graph, you can see that the frequency component is centred around 12 Hz instead of 0.4 Hz where it should be. This is what is being saved in the TDMS file and it's incorrect.

Thank you,

[zaizhou.ma · Accepted solution]

Hi,

As my understanding, you are trying to log the PSD to "Power Spectral Density" channel, but you do it wrong with double array. TDMS write don't accept cluster as input, but accept waveform.  I have updated the VI and the PSD in TDMS file viewed as

[Donners]

Thank you zaizhou,

You have no idea how long I've been trying to work this problem out.