Objective and subjective approaches to the force and displacement characteristics of input devices used by the disabled

S. August, P. L. Weiss

Research output: Contribution to journalArticlepeer-review


This study was designed to determine how well therapists were able to estimate the mechanical characteristics of adapted switches. This was accomplished using two related experiments. In the first experiment, objective data characterizing the activation force-displacement trajectories for eight commonly used adapted switches were collected. In the second experiment, subjective data identifying the relative ranking of activation force as well as activation displacement by experienced and novice therapists were compiled. The major finding was that although therapists' subjective estimates of activation force and displacement were reasonably good there were specific areas of weakness that should be rectified with quantitative, objective data. In particular, subjective estimates of the mechanical properties appeared to be inadequate when used to evaluate switches separated by only small differences in force or displacement and for those whose properties were larger or smaller than their expected values. Possible difficulties in dissociating activation force and displacement were also noted. The technical and clinical implications of these results are discussed.

Original languageEnglish
Pages (from-to)117-125
Number of pages9
JournalJournal of Biomedical Engineering
Issue number2
StatePublished - Mar 1992
Externally publishedYes

Bibliographical note

Funding Information:
The first author was supported by a student scholarship from the Medical Research Council of Canada. Funding was by the Natural Science and Engineering Research Council of Canada and the Rick Hansen Man in Motion Fund. Thanks to Dr I.W. Hunter and Mr S. Lafontaine at McGill University for the design and construction of the apparatus and computer programs.


  • Adapted access
  • adapted switches
  • disabled
  • keyboard
  • mechanical characteristics

ASJC Scopus subject areas

  • Biophysics


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