area under the psd graph from daq

Hi all,

Iwould like toclassifythe signals from measurement. Afterseeingthe resultsofthe psd graphs, the graph area of each sample is  signal is different. 

I think I can classifiy the sample from the area of the signal in the freqwency domain (between 200-800Hz).

I have try to use intergration.vi but the result is not change significanly, eventhough there are any change in the graph.

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Is there something wrong with my code or the value is to small so I cannot see the difference?

Another approach to classify is to summing the amplitudes of the frequency (from 200-800hz), but I still don't have any idea to find this approach.