EMG Software

Main Features

Analysis Software: EMG Raw Data - (mV on the y axis and the time in seconds on the x axis) the peaks represent periods of muscle activation (muscle contraction)

EMG Raw Data

Analysis Software: EMG Work Done

EMG Work Done

Analysis Software: Frequency Analysis – Moving from data with respect to time to data with respect to frequency

Frequency Analysis

  • Adjust the gain of an EMG sensor. This allows the user to increase the sensitivity with choice of five settings giving peak to peak readings of:
    +/- 6000 mV, +/- 2000 mV, +/- 600 mV, +/- 200 mV, +/- 60 mV (DataLITE)
  • Control the overall bandwidth of the EMG sensor with a choice of settings: 10 - 250, 470, 950, 5000Hz (DataLITE)
  • Transfer data to memory for display, analysis and saving
  • Open an unlimited number of data files with the option to track the time axis across all files allowing display and analysis for a large number of channels
  • Waveform display in multiple windows and formats with full zoom, scroll and area marking facilities, option to split, tile and cascade windows
  • Link multiple files together to synchronize data from multiple units
  • Engineering units with custom scaling ability on all traces independently
  • Each recorded file is both time and date stamped
  • Independent upper and lower alarm levels both audible and visual
  • File save, load and export facilities with many files simultaneously
  • Graphs and Results may be pasted into other Window applications such as Microsoft Office
  • Comprehensive filtering (see below)
  • Power Spectrum
  • X-Y graphs
  • Multiple traces per window
  • Unlimited number of windows
  • Markers – time and/or Y axis
  • Paste the graph and graph key to clipboard
  • Full trace management (change line width, color, background color etc.)
  • Export as ASCII or Wave file
  • Calculations:- minimum, maximum, mean, no. of excursions, no. of repetitions, auto Y2 - Y1 calculation
  • Filtering:
    • rectify
    • average
    • RMS
    • velocity
    • median
    • mean
    • integrate
    • offset
    • scale
    • median frequency
    • mean frequency
    • EMG work done
  • Power Spectrum Graph (linear and logarithmic)
  • FFT high pass filters:- remove DC, remove very low frequencies
  • FFT window functions:
    • Rectangle / Flat top
    • Triangle / Bartlett
    • Blackmann standard
    • Blackman Opt
    • Hamming
    • Hann

As soon as a file is opened it is displayed as a raw EMG file and may then be subject to any or all of the features listed above. The data may be left as a whole or truncated into smaller files of specific data for further analysis. Of course not only EMG data may be displayed at any one time. The Y axis may be labelled with any units governed by what sensors were connected at the time of recording, e.g. Kg or lbs for force or degrees for limb movement. These units are then saved with the file and automatically compute every time the file is reopened.

The digital inputs are displayed on a separate graph to the analog inputs. Using this facility toe contact and heel off may be obtained using the contact switch assembly type no. FS4.

Once an EMG waveform has been obtained, it is often necessary to process the waveform to extract useful information. The type of analysis depends upon the application but the following guidelines may be helpful:

  • EMG waveforms are fundamentally bursts of random signals with certain characteristics that indicate timing, force and fatigue.
  • After acquiring a waveform, remove unwanted sections of the trace. There is often a period before the activity of interest and a period after - removing these reduces the data and speeds up subsequent processing.
  • Display the waveform as an RMS signal to obtain meaningful amplitude values. See RMS Filter for further information.
  • As an alternative to an RMS display, rectify and then average the signal to produce a mean absolute waveform.
  • Use the median frequency filter to estimate muscle fatigue. See the section Median Frequency Filter for further information.
  • Frequency analysis only has a meaning for muscle activity where the length of the contracting muscle remains constant.
  • Several filters may be cascaded. For example, the RMS value can be produced followed by a median frequency filter. See the Filters Overview section for further information.
  • To measure muscle timing, be careful not to apply too much filtering. Taking an average over many samples will effectively delay the onset of muscle activity as seen on the filtered waveform.

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