Thank you.
Sum is not very meaningful because some elements are positive and ohters are negative. RMS is probably a better measure.
The data set in the VI you posted has almost nothing significant in the 200-800 Hz band. The overall spectrum shows a rolloff with increasing frequency but no "interesting" spectral features. The raw data has an average DC component of about 5.7 with a peak to peak variation about one tenth of that. Removing the mean before other processing may be useful.
You may not need a filter at all. If you take the RMS value of the spectral components representing 200-800 Hz or whatever bandwidth you need, it is about the same as the RMS of the spectrum of the filtered data.
In the attached version I placed a constant obtained from the Waveform indicator inside the Enabled case of a Diagram Disable structure. The disabled case contains the DAQ Assistant. The mean is subtracted to get rid of the large DC component. The RMS of spectral components from 200 to 800 Hz is calculated.
Lynn