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spread sheet file to the formula loop

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Accepted by topic author KK54321

Hi GerdW,

Thank you for your help,

I have exactly created VI as you mentioned above. But I am unable to get the plots for FFT, IFFT, FFT2. Instead I am getting an 1D array. I have attached the VI for your view. Could you please help me with this. Also, I need multiply with hann window function to the first FFT then need to take IFFT.

 

Thank you

KK

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Message 11 of 22
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Thank you. I figured it out.

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Message 12 of 22
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Hi GerdW,

I have incorporated all your suggestions, Now I am moving to the actual program as follows, (goal is to educe the spectral noise to get a clear spectrum)

1. Load and convert spectrum from wavelength to wave number

2. take FFT

3. Multiply with Hann window

4. IFFT.

Some how I made the above steps, and my final spectrum looks good. But I am facing a problem where the spectrum peaks are repeating if you see the plots its like mirror image. How to avoid this. Could you please help me with this. I have attached the VI for your view.

 

Thank you

KK

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Message 13 of 22
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Hi KK,

 

do you remember my older message?

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Message 14 of 22
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Sorry I forgot to down convert. Please find the attached VI.

 

Thank you

KK

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Message 15 of 22
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Hi KK,

 


@KK54321 wrote:

I have incorporated all your suggestions,


No, you have not…

 


@KK54321 wrote:

2. take FFT

3. Multiply with Hann window


2. Why is there still a PtByPt function used? I already told and showed you to use the "regular" functions!

3. I don't see tis in your VI. And I already showed you how to apply a Hanning window…

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Message 16 of 22
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Hi GerdW,

Thank you for your reply. Yes I have created a similar similar VI as you suggested. But I am only seeing noise in the final IFFT. I suppose to get clean spectrum without noise, that is the goal. Then I modified it to see some peaks in the final IFFT.So here I use PtByPt VI to get window function and multiplied it with FFT, then i took IFFT, finally i see some peaks. The Vi you suggested, there I need to multiply with Hann widow and FFT then use IFFT. I could not find any option to choose window size. is it possible with the labview.

 

Thank you

KK

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Message 17 of 22
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Hi KK,

 


@KK54321 wrote:

But I am only seeing noise in the final IFFT. I suppose to get clean spectrum without noise, that is the goal.


There is a misconception: you don't get a spectrum from an InverseFFT!

The IFFT converts data from frequency space to time space…

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Message 18 of 22
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Hi GerdW,

 

Thank you for your reply. IFFT converts freq - time space that's true. But the actual FFT will be done on the 1D array, that will be y-axis (intensity in our case). I have attached an image from a research article, where they have done the same process. So here I am trying to do the same process. Please let me know if you have any suggestions for me.

 

Thank you

KK

 

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Message 19 of 22
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Hi,

I have a spectrum with background and some noise. I need to get rid of these effects and make a clean spectrum. I have made a labview code for this purpose. Here are the steps for the code,

1. Program loads the data file and converts it to wave numbers

2. Taking the FFT of wave numbers spectrum

3. Multiply with gaussian window

5. Then IFFT,

My final spectrum looks good, and i am able to reduce the noise, but still background is present in the final spectrum. But here the problem is if I given a clean spectrum it produces some extra noise to it, also adding extra peaks to the final spectrum. Can someone help me with this. I have attached the VI and data file. We can also multiply with a high pass filter with FFT and then do IFFT to reduce the noise, but i am not sure how to do this in labview, I have attached an image for this process from an research article.

 

Thank you

KK

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Message 20 of 22
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