Frequency Measurement

[razor149]

I am taking an ECG signal(simulated) through thr NI USB 6009, as input.

When I display the waveform on a waveform graph, I can use the cursors to pin-point amplitude etc.

But is there any way I can directly display the frequency of ECG or sine wave, or any other peiodic signal ?

Thank you.

[ABCPrograms]

Hi Razor,

As far as I know, it's not possible, but I'm no Expert 😉

What you could do is use the FFT analysis VI to get the frequence of a certain graph.

You can use this execute this VI everytime there is a change on your graph for instance.

[Steve.J]

Yes - the easy way is to position two cursors on the waveform at points representing the period of the waveform.  You can read the X-index of each cursor and subtract and use this to calculate the time interval (period) knowing the sampling rate.  The inverse of the period is the frequency of the periodic waveform.

By the way - please visit our Biomedical User Group at www.ni.com/biomedusers

Steve

[razor149]

Thank you very much for your suggestions!

Since there is no direct method, I will try out both methods listed above.

I actually wanted automatic calculation of frequency. Since I am new to LabVIEW, I think it may take some time to figure out how to implement alternate solutions.

Any VI's present as an example?

Thank you again.

[ABCPrograms]

Hi,

This is a VI you could use.  You wire your graph as input and get the spectrum of your graph as output.

More help on this VI can be found here

the outpust will be something like the image in attachment.  You will get a peak at the frequence which apears the most.