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Frequency Response Function (FRF)

Hello LabVIEW Community!


I am working to get a basic modal analysis code in LabVIEW. I am using an Impact Hammer for the input signal and an Accelerometer for the output signal with an NI DAQ. I want to replicate the modalfrf function from MATLAB here i.e. to get amplitude, phase, and coherence using these two signals. I am also interested to save all the data as well. Kindly help.

PS- I used the SI Estimate FRF VI from the 'Advanced Signal Processing Toolbox', but I am not getting the required results. Also, the Modal Analysis of Plate VI is too complex to use for practical purposes. It will be great if someone can help me understand these VIs as well.


Thank You

Deepak Kumar


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Are you looking to learn LabVIEW (expect to spend a few months, at a minimum!) and write the code yourself, or are you looking to hire a LabVIEW Developer (an "expert") to do this project for you, and perhaps also provide a tutorial experience?  


Bob Schor

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Dear Sir/Ma'am


I am not looking for any expert to do this project on my behalf.

I am new here in the community and in a learning phase. I just want to know how FFT and FRF can be done in LabVIEW using any VI. An explanation of the above-mentioned VIs (in query) will be helpful too.


Deepak K

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Try this one:





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A simple example for the VI that Bert points to can be found here:
<LabVIEW>\examples\Signal Processing\Waveform Measurements\Frequency Analysis of a Filter


For FFT, you could take a look at either of the following:

<LabVIEW>\examples\Signal Processing\Waveform Measurements\Amplitude Spectrum (sim).vi

<LabVIEW>\examples\Signal Processing\Transforms\FFT and Power Spectrum


Generally, the Example Finder can help you find examples by keyword or task. 

NI Sound and Vibration
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Sound and Vibration Toolkit also includes many examples for measuring FFT and FRFs. Specifically, the SV Toolkit includes a sample project for Impact Test. You could install the toolkit and evaluate the sample project under the Evaluation License. The sample project includes software triggering to detect impacts as well as limits criteria to detect double hits, overloads, and other signs of a mishit. 


<LabVIEW>\ProjectTemplates\Source\Sound and Vibration\Impact Test\Impact Test.lvproj

NI Sound and Vibration
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