Capturing peaks

[KowdTek]

Hello! Image below is gathered from oscilloscope and I used a waveform generator to come up with this graph. What I'm trying to do is replicate this using LabVIEW.. just using FFT power spectrum vi I can only see "peak 1" (still new to this) What can I do to capture peak 2 & 3? Any example or help would be appreciated...

Here's my SW/HW:

LV 2009

PCI-6259

Thanks!!

[battler.]

Is the image you show a frequency spectrum?

Do you mean you want to capture the amplitude at a particular (or any) frequency?

The first step would be to capture your signal using your DAQ.  There are heaps of examples shipped with LV and/or try a search of ni.com.  Use the DAQ assistant if you're new to it.

Once you have a signal (some data) you can use the Signal Processing VIs in the function pallette to do an FFT.

There are all sorts of ways to extract the peaks; some simple, others complicated (probably more reliable and robust).  Apply some windows and/or filters.

[aeastet]

Something like this

[KowdTek]

Thanks for the quick reply.

Yes, the oscope was set to FFT math.

I guess that's the best way of describing it, I want to capture the amplitude at any frequency. Actually, in the actual test I'll be expecting to see several peaks and would like to capture the first 3 with the highest amplitude.

Thanks again!!!