Missing EMG Signal Frequency between 100Hz and 110Hz

[ArvinB]

Greetings,

I've been working on an EMG device where I use LabVIEW to receive the signals, save to LVM file and also analyze the signals. Attached is my analysis interface and two sample files. My problem is that, for every good EMG signal I get, the frequency spectrum seems to behave similarly to the prescribed EMG signal frequency spectrum except that there are missing amplitudes from about 100 Hz to 110Hz, as shown in the image below. This happens to all my EMG signals, why is this happening? what is causing this? and what does it mean to my signal?

It's my thesis defense on Thursday so I need help fast. Thank you.

[DFGray]

Two issues:

1. The files you posted are simple ASCII files, not LVM.
2. Your time values are not evenly spaced.  Some are pretty wildly off.  This will definitely effect your frequency analysis, which assumes evenly spaced data.

To fix this, read the data in using the Read from Spreadsheet File VI from the File I/O palette, then use one of the resampling VIs in the signal processing palette to convert your variable length timestamps to evenly spaced.  Then run your FFT.  You may also consider changing your data acquisition so it is evenly sampled.  If you are using a DAQ card, this is fairly simple.  Post your acquisition code if you want pointers.