EMGLAB FORUM >HELP! Linear envelope detection

  Subject:   HELP! Linear envelope detection
From:   Lost in space Date:   26 Jan 2012 7:08 am  
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  I am using a clinical sEMG system which has inbuilt software that produces the linear envelope of the EMG signal by full wave rectifying it and then passing it through a low pass filter at 3Hz. I am new to EMG and would really appreciate some explanation about the low pas filter used here. It must mean something difference to a "normal" low pass filter because how would I have any signal left with such a low cut off? (the muscles I am looking at produce activity around 50-200Hz). Does the 3Hz cut off actually mean that it is taking a moving average of the signal 3 times a second? Or what? PLease help me! I can't find the answer in any books or websites!!!!
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