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Getting natural Frequencies of Fixed-Free beam

I am using Sound and Vibration assistant and i connected my acceleromter and hammer to my DAQ device and i want to get the natural frequncies of beam 

 

Thanks in advance

 note :  I am a beginner at using Labview

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Message 1 of 9
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So are you able to get any readings from your accelerometer and hammer at all in LabVIEW? Or are you needing help actually getting the devices to communicate with LabVIEW? Just need a little clarification in what you actually need help with.

 

Have you looked over any of the examples that are specific to the Sound and Vibration Toolkit? They can be found in the NI Example Finder (Help » Find Examples » Toolkits and Modules » Sound and Vibration). These shipping examples may be of some help for you getting started. Here is also a link to some Sound and Vibration exapmles:

http://www.ni.com/white-paper/6107/en

dK
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Message 2 of 9
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I was able  to connect the accelerometer in Labview (making basic VI ) but could  not get reading at the sound and vibration assistant

and my goal is to get the natural frequencies for the beam , I know that I need to make impact test and get the 

frequency response graph using the accelerometer and the hammer signals as input signal and trigger

 

I understand what I want to do but I can not perform it on the sound and vibration assistant

 

Thanks in advance

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Message 3 of 9
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This video may be of some help for you:

https://www.youtube.com/watch?v=tnHBP7e6JX0

 

Also, going through the Getting Started with the NI Sound and Vibration Assistant PDF file has lots of great information:

http://digital.ni.com/manuals.nsf/websearch/0AFDDDCEEB04E6D986257368006A380D

 

If you are still having trouble getting a reading with the sound and vibration assistant, just let me know what procedure you are following to try and acquire the signals so that we can make sure we are not missing anything.

dK
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Message 4 of 9
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 although I am using a filter a very wide range of frequencies appears in the output graphs and I think the graphs are giving the wrong answer(I performed simulation on ansys ).

My supervisor told me to use scaling feature with the hammer signal but I do not know why and how .

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Message 5 of 9
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Dont' use the frequency response step.  That might work if you had a regular forcing function that you wanted to compare your response signal to.  You re doing a simple hammer rap.

 

Use a regular FFT such as Power Spectrum to analyze your data.

 

Beyond that, your input waveform just looks very noisy.

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Message 6 of 9
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May you tell me the function of the custom scaling in the channel settings and can this help me reduce the noise in the input waveform or is there another way  , and why does the output graph has very wide range of frequency although I put a lowpass filter with cutoff 990 Hz

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Message 7 of 9
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Custom scaling will allow you to change from the basic voltage reading of millivolts to some other reading such as engineering units.

 

You are sampling at a higher frequency.  You may be filtering to a lower frequency, but that doesn't change the underlying timebase for your waveform.  So any FFT of that signal will still be established up to the Nyquist frequency of your sampling rate.  Just that the frequency components of your signal that are higher than your filter will be removed.

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Message 8 of 9
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i am also facing same problem

i get acceleration and frequency plot

but i cannot find out natural frequency from that data.

acctually i do not know how to find out natural frequency from that plot.

and i want block diagram of labview .

even i want to start my recoder when i impact hammer is take place so i can get actually reading

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Message 9 of 9
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