Instrumentation Back to EMG main page

Volume II (Second Edition) : Atlas of EMG Waveforms
Chapter 1: Instrumentation

Objectives
1 - Review the basic components of an EMG system.
2 - Study the effects of filter settings on EMG waveforms.
3 - Introduction to digital EMG signal processing.
4 - How to make manual measurements.
5 - Concentric vs Monopolar needle electrodes.
6 - Strategies for reducing noise.
The Instruments:
Analog to Digital

Model M2 Electromyograph

Model JM

Oxford Synergy N2

Block Diagram

Signal Analysis on Digital Electromyograph
Electrodes

Concentric Needle Construction

Concentric Needle Recording

Monopolar Needle Construction

Monopolar Needle Recording
Cables

Leads and Cables

Minimising Ambient Noise
Amplifer

Principle of Differential Amplification

How Noise is Attenuated

Common Mode Rejection Ratio

Improving Signal/Noise Ratio
Filters

Principle of Filters

Signal and Noise

Low Frequency and Insertional Activity

Low Frequency and Motor Unit Potential

High Frequency and Motor Unit Potential
Analog to Digital
Conversion

From Analog to Digital

Theory and Theorems
Aliasing

When Sampling Rate is Low

Aliasing in EMG

Spontaneous Activity

Technology or Pathology
Trigger and
Delay Line

Amplitude Trigger

Assessing Motor Unit Potential
Averager

Averaging Motor Unit Potential

Noise Reduction with Averaging
Manual
Measurements

Amplitude

Duration

Firing Rate <10 Hz

Firing Rate =10 Hz

Firing Rate >10 Hz

Firing Rate =20 Hz
Electrical Safety

Unsafe Operation

Safe Operation


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