Windowing function in LV before FFT

[krishk24]

Hello

I am having some trouble with respect to windowing in LV2013. the shape of the windowed time domain waveform looks wrong.

Here is the window function - C:\Program Files (x86)\National Instruments\LabVIEW 2013\vi.lib\Analysis\4window.llb\Hamming Window (DBL).vi

I am trying to extract the tone amplitude from the frequency domain and the value is wrong when windowing is enabled.

But it is correct when windowing is disabled.

appreciate any help that is offered. thanks

[krishk24]

Sorry never mind, I did not have right scaling on X and Y axis.

the problem still remains - the tone amplitude from frequency domain does not match the unwindowed waveform. But all works out ok in matlab sim.

[johnsold]

The GNSSSignalMag.vi is missing. Is it part of some toolkit?

I replaced the Express Simulation VI with Sine Waveform.vi from the Signal Conditioning palette so that I can control things like Fs. When I do that and look at the maximum value in the adjusted spectrum, it remains the same whether windowed or not. 

Extract Single Tone Information.vi uses FFT techniques for measuring tone information. You can open its block diagram to see how NI did things.

It has been a while since I used MATLAB but I think they use a different scaling method for FFT.

Lynn