how to pick dominant frequency

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stephy1

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if i have a signal with amplitude versus time and i want to find wether a particular value/range of frequency is present over there in my signal. What steps should i take?

For example i have above signal from accelerator and i want to know whether it contains 20 Hz signal or not?

Should i convert it into frequency domain or what?
I am using LabVIEW for my signal processing.
 

Hi,

To explicitely answer this question:
Should i convert it into frequency domain or what?
Click to expand...
Yes, it's the only way, I think.

But thinking further I have to say:
The signal will always contain some 20Hz components. The question is: how much.

A lot of thought cross my mind:
* what information do you really need?
* where does this 20Hz come from?
* what's your sampling frequency?
* is the sampling frequency an integer multiple of this 20Hz? (To use a DFT)
* is the sampling frequency an integer multiple 2^n of this 20Hz? (To use an FFT without windowing)
* what bandwidth do you expect?
* how fast or how often do you need this information
..and a lot more...

There are several solutions:
* analog filters
* lock in amplifiers
* DFT
* FFT
....

Klaus
 

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