The Open UniversitySkip to content
 

Myoelectric electrode amplifiers: rejection of unwanted common mode signals

Poulton, Adrian (2008). Myoelectric electrode amplifiers: rejection of unwanted common mode signals. In: Myoelectric Controls Symposium MEC 08, 13-15 Aug 2008, Fredericton, New Brunswick, Canada.

Full text available as:
Full text not publicly available
Due to copyright restrictions, this file is not available for public download
Click here to request a copy from the OU Author.
Google Scholar: Look up in Google Scholar

Abstract

It is well established that electrode amplifiers for myoelectric control require high input impedances, high common-mode rejection ratio (CMRR) and mains frequency notch filters to cut out unwanted noise. Further, they generally offer a high degree of d.c. isolation. However, it is not generally recognised that the isolation between the skin ground electrode and the common lead may reduce at higher frequencies, and this can create a path for interfering common-mode signals. Harmonics of the mains frequency may be a particular concern as they are not rejected by the notch filter. Common-mode interference can adversely affect prostheses in electrically noisy environments, as long lead runs may act as antennas. Moreover, because of the nature of common-mode, screening the leads may have little effect. Measurements were made on a commercially available electrode amplifier to quantify the effect of injected common-mode signals with and without imbalance in the electrode contact impedances. The results presented here indicate that a low impedance a.c. path between input and output can contribute to the effect of common-mode injection. Analysis of the common mode mechanism is presented and possible alternatives are discussed.

Item Type: Conference Item
Copyright Holders: 2008 The Author
Academic Unit/Department: Mathematics, Computing and Technology > Computing & Communications
Item ID: 25825
Depositing User: Adrian Poulton
Date Deposited: 04 Jan 2011 10:29
Last Modified: 12 Dec 2012 20:05
URI: http://oro.open.ac.uk/id/eprint/25825
Share this page:

Actions (login may be required)

View Item
Report issue / request change

Policies | Disclaimer

© The Open University   + 44 (0)870 333 4340   general-enquiries@open.ac.uk