How to get power spectrum manigtude at the first harmonic

[dot55]

I use PXI 5122 to capture signals from (2) channels 0-1.Channel One output of my device is 1Mhz and a adjacent channel should be very low signal due to cross talk.   I use power spectrum VI but it does average power sprectrum. I would like to extract just the magnityude

at 1MHZ ( fundamental component od my output signal) in frequency domain.

Per attched graph, I want the different in dB between two signal 1 and 2. Instead of reading off the chart is there a way

to extract that single component magnitude.   See attched VI and frontpanel for referecence. 

Thanks for your help.

[dot55]

forgot one more attached .

[DFGray]

You can use Peak Detector.vi to find peaks in a signal.  Better yet, use the Extract Multiple Tone Information.vi to get the power spectrum and a list of peaks in one operation.  Extract Multiple Tone Information.vi will do a better job, since it does a peak fit and will return subsample accurate information.

[dot55]

Thanks for your reply.  My output is a cluster I cannot wire to extract multitone info vi.

see attched vi (8.6).

[dot55]

I forgot to tell you that I already use this extract tone VI. But it give anplitude in volt which is not what I want.

 I want to get the peak of the 1st hramonic in dB , from the power spectrum cluster as mention in the first post.

Thanks

[dot55]

I found the answer. I just have to split the cluster of power spectrum output into two and search for max value. Thanks