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Freeze and Frequency Analysis

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Freeze and Frequency Analysis

Hey,

I am new in Labview and for my project i have to do a FFT analysis. I use a NI SCB68a and a MEMS Adxl335 sensor for vibration and frequency analysis.

I tried around with while- and for-cases, but i cant solve it and so I have 2 Questions to you:

How can i get my signal visable in a graph-chart for e.g. 10 seconds? Now its just for some milliseconds, played arround with the rate and the samples but no change. Then i got the plan to make it with a loop but i dont now how.

Plan is:  push the trigger for recording the measurements. so far its working (for some milliseconds)

and after the vibration measurement like 10 seconds, with an FFT i wanna analyse the graph manually.

 

Thanks a lot for you help. 

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Message 1 of 42
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Re: Freeze and Frequency Analysis

Hello Gregory88,

you can set the chart histroy length, this defines how many samples are stored inside of the diagramm.(right click on the diagramm)Unbenannt.PNGWhat i recommend is tu use a produce consumer structure and making the FFT in the consumer.

sample.pngHope it helps.

best regards
Alexander Glasner
CER AES
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Re: Freeze and Frequency Analysis

hey duffy,

thanks for the reply.

i think it´s because you´ve labview '16 i can´t open your recommend VI :/ is it possible to make it run under my '15?

ok i found the chart history length, but if i play arround with it nothing changes... i mean the more important chart is the one below cuz i thought i could make there the FFT.

 

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Re: Freeze and Frequency Analysis

Hello Gregory88,

saved down to 2015

best regards
Alexander Glasner
CER AES
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Message 4 of 42
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Re: Freeze and Frequency Analysis

hey alex,

thank you, also for the VI, now i can open it but it isn´t working Smiley Sad

I setted everything and i in the DAQmx i could see my signal, but not if run the VI. 

And a Question: this makes a FFT over the whole time like 10seconds? Or is it also possible to analyse the signal at a peak or over a time like 2 seconds, you know, to be variable/flexible.

But therefore i think must be created cursors right?

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Re: Freeze and Frequency Analysis

Hello Gregory88,

 

this example makes an FFT every 10 seconds over the complete signal. In the singal chart you only see the last second.

If you want to have a variable analyse system, where you see the 10 seconds and select what region should be analysed you can use the cursor function to select the regions.

best regards
Alexander Glasner
CER AES
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Re: Freeze and Frequency Analysis

This would be the one i am looking for. Do you know if NI provides such a VI?

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Message 7 of 42
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Re: Freeze and Frequency Analysis

Hello Gregory88,

there is no ready to run function. Attached an idea from my side

sample.png

 

best regards
Alexander Glasner
CER AES
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Re: Freeze and Frequency Analysis

:/

Thank you again for the VI.

I got a error - 200279: "The VI cant keep up with the hardware recording.

Maybe the problem can be solved trough increasing the buffer, read out more often the datas, or set a special number of the samples."

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Re: Freeze and Frequency Analysis

I wanna use labview like in the following example. Like a normal oscilloscope.

https://www.youtube.com/watch?v=vkEg7P3oPvs

I tried to rebuild the VI but doesn´t work at all. Smiley Sad

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