An artefact desynchroniser for use with visual evoked potential stimulators

Technical Note


When recording visual evoked potentials elicited by a CRT raster display, driven from a frame-synchronised stimulus generator, artefacts caused by magnetic fields originating from the CRT field coils may seriously contaminate the recordings. This interference cannot be removed by signal averaging as it is time locked to the frame rate of the CRT. The circuit described here effectively desynchronises the interference, enabling the signal averaging process to reduce the artefact without the bandwidth restriction and resultant distortion of the recording which would be caused by lowpass filtering.


Artefact Averaging Bandwidth CRT Dithering Filtering Magnetic fields Synchronous Visual Evoked Potentials Visual stimulators 


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  1. Evanich, M. J., Newberry, A. O. andPartridge, L. D. (1972): ‘Some limitations on the removal of periodic noise by averaging’,J. Appl. Physiol.,33, (4), pp. 536–541Google Scholar

Copyright information

© IFMBE 1999

Authors and Affiliations

  1. 1.Department of Medical Physics & Clinical EngineeringRoyal Hallamshire HospitalSheffieldUK

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