How to design multirate filter system for EMG signals

Christian - 2020-12-29T10:01:41+00:00

Question: How to design multirate filter system for EMG signals

I am using Delsys Bagnoli EMG System to acquire sEMG from forearm muscles. When I use Delsys EMGworks application, output signals are clean as expected with minor interferences. However, when I use the following Matlab script to acquire the  signal unusual signal pattern occured (spikes). the image of frequency domain of the Data (Red color frequencies contains EMG information) acquired from Matlab script is attached herewith. I want to know why this happens and how to remove thoses spikes the Matlab script: %% EMG initialize raw = zeros(1,6); % EMG setup emg = daq.createSession('ni'); ch1 = addAnalogInputChannel(emg, 'Dev1', 0, 'Voltage'); ch2 = addAnalogInputChannel(emg, 'Dev1', 1, 'Voltage'); ch3 = addAnalogInputChannel(emg, 'Dev1', 2, 'Voltage'); ch4 = addAnalogInputChannel(emg, 'Dev1', 3, 'Voltage'); ch5 = addAnalogInputChannel(emg, 'Dev1', 4, 'Voltage'); ch6 = addAnalogInputChannel(emg, 'Dev1', 5, 'Voltage'); emg.Rate = 4000; % sampling rate lh = emg.addlistener('DataAvailable',@stopWhenExceed); emg.NotifyWhenDataAvailableExceeds = 400; % data per one feature set (total of all channels) emg.IsContinuous = true; emg.startBackground(); while 1 % check the existing time.mat file time(end + 1 : end + 1, 1) = str2double(datestr(now,'SS.FFF')); pause(0.01); % this pause should be there to acquire EMG data if (getGlobalSx==0) % if new set of data is available data = getGlobalx; % aquire data setGlobalSx(1); end raw(end +1:end+400, : ) = data; end

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Expert Answer

Neeta Dsouza answered . 2025-11-20

I realized that the pause we provide to the code to acquire EMG data should be equal to the,

 

emg.NotifyWhenDataAvailableExceeds / emg.Rate

while 1
   
    % check the existing time.mat file
    time(end + 1 : end + 1, 1) = str2double(datestr(now,'SS.FFF'));
    
    % ---------------------This value should be 0.1.-------------------------------
    pause(0.1); % this pause should be there to acquire EMG data
    if (getGlobalSx==0)           % if new set of data is available
        data = getGlobalx;          % aquire data
        setGlobalSx(1);
    end
    raw(end +1:end+400, : ) = data;
    
end

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